Schedule Acceleration Techniques Using a CM

College of Engineering Schedule Acceleration Techniques Using a CM By PI: Dr. Jesús M. de la Garza, Vecellio Professor Graduate Student: Ms. Daniela Escobar Hidrobo Final Report September 1, 2006 Invent the Future VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY An equal opportunity, affirmative action institution

Table of Contents I. Introduction 5 II. The Construction Manager 6 Agency CM 6 CM at risk 6 Project Delivery 6 Construction management and project delivery method 6 Traditional approach (design-bid-build) 7 Multiple-prime contracting 7 Design-build 8 At-risk construction management 8 III. Schedule acceleration techniques 10 A. Good management practices during project development for achieving reduced delivery times 11 1. Start-up driven scheduling 13 2. Participative management 13 3. Resources 13 4. Pre-project planning 13 5. Alignment 13 6. Well-defined organizational structure 13 7. Pareto's law management 14 8. Employee involvement 14 9. Realistic scheduling 14 10. Construction-driven scheduling 14 11. Concurrent evaluation of alternatives 14 12. Avoid scope definition shortcuts 14 13. Use of electronic media 14 14. Constructability 15 15. Freezing of project scope 15 16. Reusable engineering 15 17. Non-traditional drawing release 15 18. Supplier/engineer early interaction 15 19. Materials management 15 20. Material coordination 16 21. Prioritize procurement of material 16 22. Efficient packaging for transportation 16 23. Material I.D. on purchase documentation 16 24. Testing/inspection 16 1

25. Multiple suppliers 16 26. Supplier submittal control 17 27. Field management 17 28. Safety in workspace 17 29. Aggressive project close-out 17 30. Detailed plan 17 31. Determine system testing requirements 17 32. Zero accidents techniques 17 B. Freezing of project scope a. Technique 18 b. Implementation 18 c. Advantages 19 d. Key elements to ensure a high degree of success 19 e. Disadvantages 20 f. Applicability and use 21 C. Constructability review a. Technique 22 b. Implementation 23 c. Advantages 26 d. Key elements to ensure a high degree of success 27 e. Disadvantages 28 f. Applicability and use 28 g. Other special characteristics 28 D. Cycle time analysis a. Technique 34 b. Implementation 34 c. Advantages 35 d. Key elements to ensure a high degree of success 35 e. Disadvantages 35 f. Applicability and use 36 E. Concurrent engineering a. Technique 37 b. Implementation 38 c. Advantages 38 d. Key elements to ensure a high degree of success 39 e. Disadvantages 40 f. Applicability and use 40 g. Other special characteristics 40 F. Overlapping sequential design activities based on concurrent engineering a. Technique 42 b. Implementation 43 c. Advantages 49 d. Key elements to ensure a high degree of success 49 e. Disadvantages 49 2

f. Applicability and use 50 g. Other special characteristics 50 G. Lean design a. Technique 52 b. Implementation 52 c. Advantages 54 d. Key elements to ensure a high degree of success 55 e. Disadvantages 55 f. Applicability and use 56 H. Value engineering a. Technique 57 b. Implementation 57 c. Advantages 58 d. Key elements to ensure a high degree of success 59 e. Disadvantages 59 f. Applicability and use 59 I. Four-dimensional visualization of construction scheduling a. Technique 61 b. Implementation 61 c. Advantages 62 d. Key elements to ensure a high degree of success 63 e. Disadvantages 64 f. Applicability and use 64 J. Overlapping sequential construction activities based on concurrent engineering a. Technique 65 b. Implementation 66 c. Advantages 67 d. Key elements to ensure a high degree of success 67 e. Disadvantages 67 f. Applicability and use 68 g. Other special characteristics 68 K. Fast-track a. Technique 71 b. Implementation 71 c. Advantages 71 d. Key elements to ensure a high degree of success 72 e. Disadvantages 74 f. Applicability and use 75 g. Other special characteristics 75 L. Just-in-time delivery a. Technique 82 b. Implementation 82 c. Advantages 82 3

d. Key elements to ensure a high degree of success 82 e. Disadvantages 82 f. Applicability and use 82 M. Lean construction 1. "The Last Planner": Shielding production through weekly work plans 84 a. Technique 84 b. Implementation 85 c. Advantages 88 d. Key elements to ensure a high degree of success 89 e. Disadvantages 90 f. Applicability and use 90 2. Improving labor flow reliability for better productivity through the use of buffers 90 a. Technique 90 b. Implementation 91 c. Advantages 93 d. Key elements to ensure a high degree of success 93 e. Disadvantages 94 f. Applicability and use 94 N. Optimization of construction operations through simulation and genetic Algorithms a. Technique 96 b. Implementation 97 c. Advantages 99 d. Key elements to ensure a high degree of success 100 e. Disadvantages 100 f. Applicability and use 101 O. Time-cost trade-offs a. Technique 102 b. Implementation 102 c. Advantages 110 d. Key elements to ensure a high degree of success 110 e. Disadvantages 111 f. Applicability and use 113 IV. Summary 114 V. References 115 4

I. Introduction In today s businesses owners rely on first-to-market product strategies to gain competitive advantage and increase profit margins. Within the construction industry, this has created a growing need for enhanced performance delivery systems that can achieve successful project delivery in shorter time. Owners demand greater improvements in the quality of project construction at lower costs and within reduced schedules. The completion of project s time milestones is a crucial factor because not meeting them usually involves significant economic impacts to the owner while time savings can lead to profit improvements. However, the increasing complexity of project technologies along with the competitive nature of business oblige the owner to make changes in project scope at the last moment, hindering project delivery within the anticipated time. Moreover, today s market opportunities and competitiveness within the industry can also force the owner to accelerate project execution and demand earlier completions. In the presence of increased demands for shortening project cycle times, research has dedicated in the last years significant time and effort in searching for the right tools and techniques to assist owners and construction managers to effectively manage time and resources aiming at expediting project execution and reducing project delivery time. Several sources of research provide the construction community with different strategies and techniques to effectively address today s aggressive schedules and tight delivery demands. The document presented herein is a recompilation of the most effective techniques available to the construction manager that enable project acceleration to achieve reduced delivery times. 5

II. The Construction Manager (CM) The Construction Management Association of America (CMAA) defines the construction manager as a provider of professional services to the Owner, the CM organizes the effort, develops the management plan, monitors the participants progress against the plan and identifies actions to be taken in the event of deviance from the plan. The CM also provides expert advice in support of the Owner s decisions in the implementation of the project. The CM can be a firm, a team of firms, or an individual (CMAA 2002, pp.3). Thus, construction management is the practice of professional management services applied to the planning, design and construction stages of a project, from inception to completion for the purpose of controlling time, scope, cost and quality (CMAA 2003). The ability of a professional CM to manage the different phases of a project has the potential to improve project s success. Construction management can be applied in two different forms: CM in an agency basis and CM at risk. Agency CM The Agency CM acts as the Owner s principal agent to advise on or manage the process from project conception to completion. Agency CM set of services can be applied to any project delivery method. Typically, the owner hires a CM to extend or supplement its own expertise and staff, and to manage the project throughout the delivery method chosen (CMAA 2002). CM at risk CM at risk provides professional management assistance to the Owner prior to construction and advice on constructability, budget and schedule considerations. The CM then converts to the equivalent of a contractor during construction as it assumes the obligations of construction execution and completion for an established price. Because of the responsibility held by the CM at risk over construction performance, CM at risk is a distinct delivery method (CMAA 2002). Project Delivery A project delivery method is a system designed to achieve the satisfactory completion of a construction project from conception to occupancy (CMAA 2003). There are numerous different approaches used in the construction industry to successfully deliver a project, and each of these may present several variations. However, the four basic delivery systems include: Traditional approach (design-bid-build) Multiple-prime contracting Design-build At-risk construction management Construction management and project delivery method Construction management is a discipline intended to provide professional services and expert support to the owner in the implementation of a construction project regardless of the chosen contract form or project delivery method. Thus, CM integrates owner and project needs by effectively managing project delivery through the application of comprehensive controls in the 6

different critical aspects of the project including time, cost, scope and quality throughout project s phases of planning, design and construction. The different systems of project delivery and its variations can lead to different construction management practices and applications. But all project delivery approaches and variations can favorably take advantage of the benefits provided with construction management services in either the agency or at-risk form. The four basic project delivery methods are briefly summarized below, along with a discussion of some of the important characteristics of CM s participation on each. The traditional approach (design-bid-build) The design-bid-build or traditional approach has been the most popular approach to deliver projects for many years. This method involves the owner, the designer, and one or more contractors with subcontractors. Thus, the owner hires a designer for the development of the design of the complete facility. Once design is completed, it is advertised so that the interested general contractors can prepare bids for the construction of the project. In most of the instances, the general contractor that submits the lowest responsive and responsible bid is selected to perform the work, and can employ subcontractors to carry out some or all components that comprise construction. The contractor is then responsible for constructing the facility in accordance with the design. Under this approach, the contractor selected is responsible for the means, methods and sequence of construction, and for the scheduling and coordination of all subcontractors, suppliers and vendors. The owner thus manages the overall process and administers all contracts. The owner can also rely on the designer for monitoring construction as an agent, or hire a CM to administer contracts and manage all the construction work. The owner can also hire a CM from project conception, thus the CM provides professional services and support in project conception and pre-planning, planning of scope, design development, contract administration, and construction management. Thus, the CM operates as the owner s agent and performs on the owner s best interest throughout the entire project delivery process (CMAA 2003). Multi-prime contracting Under multi-prime contracting the owner holds separate contracts with contractors of various disciplines, such as general construction, structural, mechanical, and electrical. The owner may hire a CM to manage project development from conception and design, and to coordinate contractors and to manage the overall schedule and budget during the entire construction phase, thus the CM functions as the owner s agent to administer the multiple contracts. Under this delivery approach, the owner holds direct contracts with the designer party and with each prime contractor. Trade construction contracts may be competitively bid or negotiation directly. Each contractor is responsible for the means and methods of construction. There are two basic types of multi-prime contracting: phased construction and full multi-prime or trade contracting (CMAA 2003). Phased construction: Under phased construction, the project is bid in phases such as site work, site utilities, and one or more general construction packages. The CM manages and coordinates the individual contracts on behalf of the owner. The owner, through the CM, has control over the overall schedule since the CM develops the schedule for bidding the individual work packages. The CM also assists the owner in managing costs throughout the phased procurement of contracts. 7

Trade contracting: Under this delivery method the owner holds contracts with each individual trade contractor. The CM is responsible for coordinating these contractors in the best interest of the owner. The success of multiple-prime contracting largely depends on the effectiveness of the coordination of the prime contractors and the overall schedule through the CM. Design-build In the design-build project delivery method the development of the design and execution of the construction of the project fall under the responsibility of one sole party or a joint-venture. Under this approach, the owner contracts with a design-build team to plan, design, construct, implement, and control the entire project from conception through completion, and sometimes through occupancy and startup. In consequence, the owner has one single point of responsibility for project delivery. Typically, a design-build firm or a joint-venture between a design and contractor firms provide all of the services required for project delivery. However, the designbuild approach can present two different variations. The first one involves the owner engaging with a developer who then selects its own design and construction partners. Another approach to design-build delivery is given when the construction party acquires complete responsibility for the project and hires its own design team (CMAA 2003). The CM comes into play when the owner decides to supplement his staff team and hire an agent to provide with professional and technical support services to guarantee that the design-build team performs accordingly to achieve the goals and objectives established by the project. At-risk construction management Under this method the CM is hired by the owner at the early stages of project development during the pre-design and design phases. The CM works with the owner and the design team to provide professional support and advice to develop the design that best benefits the owner and to provide input on the methods of construction. When design has progressed and is partially completed (50% to 80%), the CM prepares an estimate for construction performance and offers the owner a total project cost usually in the form of a guaranteed maximum price (GMP) or fixed price (lump sum). If the owner decides not to employ the CM s services for construction performance, the CM continues to perform as the owner s agent (CMAA 2003). When the CM performs the work under a GMP of lump sum, he becomes the equivalent of a general contractor or independent contractor during construction. Under this approach, the CM is completely responsible for delivering the project on time and within the pre-established budget. The CM selects the methods, means, techniques and sequence of construction, the CM is as well responsible for the scheduling and coordination of all trade contractors, subcontractors, suppliers and vendors, and can also perform sections of the work with its own resources. CM at risk also allows the CM to bid and subcontract portions of the work while other unrelated parts are still not completed. Thus, the owner and CM negotiate the GMP or fixed price for a partially completed portion of design (CMAA 2003). Regardless of the form of contract agreement and the delivery system adopted, the CM performs professional tasks and responsibilities throughout all the phases of program or project 8

implementation in the best interest of the owner and the project. With this objective the CM is expected to have the ability to make recommendations regarding (CMAA 2002): o Most effective use of available funds o Enhanced control of the scope of work o Optimal project/program scheduling options o Best use of individual project team members expertise o Maximum avoidance of delays, changes and claims o Enhanced design and construction quality o Optimum flexibility in contracting/procurement options Having identified the basic systems of project delivery available to owners and the core characteristics of each one along with the role played by the CM under each approach, in the following sections the existing schedule acceleration techniques that can be applied to any given project with the use of a CM in order to reduce project durations and improve delivery times are presented. 9

III. Schedule acceleration techniques No. Technique Pages from to Project delivery system Agency CM Multi-prime contracting Design-bidbuild Designbuild CM at risk A Essential good management practices 11-17 X X X X B Freezing of project scope 18-21 X X X X C Constructability review 22-33 X X X X D Cycle time analysis 34-36 X X X X E Concurrent engineering (CE) 37-41 X X X X F Overlapping sequential design activities based on CE 42-51 X X X X G Lean design 52-56 X X X X H Value engineering 57-60 X X X X I Four-dimensional visualization of construction scheduling 61-64 X X X X J Overlapping sequential construction activities based on CE 65-70 - X X X K Fast-track 71-81 - X X X L Just-in-time delivery 82-83 - X X X M Lean construction 84-95 - - X X N Optimization of construction operations through simulation and genetic algorithms 96-101 - - X X O Time-cost trade-offs 102-113 - - - X Table 1. Schedule acceleration techniques 10

A. Good management practices during project development for achieving reduced delivery times Control of project time is fundamental to achieve schedule compression and deliver projects in reduced periods of time. During project development from conception through planning, design, construction, until project close-out, the management and organization of time and schedules is a key to achieve successful project completion. Research reveals that a series of actions could be implemented and enforced throughout project development to give the construction manager an enhanced use of time. Below are listed a series of basic but essential management procedures that should be adopted in the execution of any given project to efficiently manage and control time with the objective of minimizing delays and reducing the time required to deliver successful projects to owners. These actions can be applied to the different phases of project development including pre-planning, design development, materials management, construction and start-up. Nonetheless, the biggest opportunities for achieving true reductions in project delivery occur in the pre-planning and planning phases before the project begins. Consequently, following good management practices during early stages of project development is imperative to increase the potential for early project completion. 11

Project delivery phase No. Description Pages Pre-planning (Agency CM) Design (Agency CM) Materials mgt. (Agency CM and CM at risk) Construction (CM at risk) Start-up (Agency CM and CM at risk) 1 Start-up driven scheduling 13 X X - X - 2 Participative management 13 X X - X - 3 Resources 13 X - - - X 4 Pre-project planning 13 X - - X - 5 Alignment 13 X X - X X 6 Well-defined organizational structure 13 X X X X X 7 Pareto's law management 14 X - - - - 8 Employee involvement 14 X X X - - 9 Realistic scheduling 14 X X - X - 10 Construction-driven scheduling 14 X - - X - 11 Concurrent evaluation of alternatives 14 X - - - - 12 Avoid scope definition shortcuts 14 X - - - - 13 Use of electronic media 14 X X - X - 14 Constructability 15 - X - X - 15 Freezing of project scope 15 X X - - - 16 Reusable engineering 15 - X - - - 17 Non-traditional drawing release 15 - X X - - 18 Supplier/engineer early interaction 15 - X - - - 19 Materials management 15 - - X - - 20 Material coordination 16 - - X - - 21 Prioritize procurement of material 16 - - X - - 22 Efficient packaging for transportation 16 - - X - - 23 Material I.D. on purchase documentation 16 - - X - - 24 Testing/inspection 16 - - X - X 25 Multiple suppliers 16 - - X - - 26 Supplier submittal control 17 - - X - - 27 Field management 17 - - - X - 28 Safety in workspace 17 - - - X - 29 Aggressive project close-out 17 - - - - X 30 Detailed plan 17 - - - - X 31 Determine system testing requirements 17 - - - - X 32 Zero accidents techniques 17 - - - - X Table 2. Good management practices for achieving reduced delivery times 12

1. Start-up-driven scheduling The Construction Industry Institute (CII) recommends, under Engineering/procurement/ construction (EPC) projects, developing the overall schedule based on the owner s needs related to the start-up dates and activities. Start-up activities define then construction dates and construction schedule, and construction establishes procurement and engineering dates (CII: The Game Planner 2004). Thus, under this approach project completion is executed and achieved as per requested by the owner. The start-up driven schedule can then be used by the construction manager for following up, monitoring and controlling progress in relation to the schedule derived from owner requirements (CII: The Game Planner 2004). 2. Participative management Participative management refers to the involvement of employees considerations and ideas to improve planning and productivity, and to reduce inefficiencies. CII defines participative management as the process of involving those who are influenced by decisions where everyone makes certain that everyone gets their needs met (CII: The Game Planner 2004, pp.12). Participative management enhances employees motivation and commitment while reducing process inefficiencies, increasing the likelihood of reducing activity durations as well. Moreover, motivation among workers ultimately results in improved labor performance and higher levels of productivity. 3. Resources It is important to assign enough and adequate resources to develop an effective project plan. Usually costs and expenses at the beginning stages of planning are minimal compared to overall project costs, and the effects that effective project planning may have over overall project duration are gigantic (CII: The Project Manager s Playbook 2004). 4. Pre-project planning Pre-project planning is the process of obtaining and developing important information with which the construction manager and the owner can assess and evaluate areas of higher risk within the project (CII: The Project Manager s Playbook 2004). The identified risk can be addressed by committing more resources, leading to the minimization of areas of potential failure or delays. 5. Alignment Alignment is defined as the condition where appropriate project participants are working within acceptable tolerances to develop and meet a uniformly defined and understood set of project objectives (CII: The Game Planner 2004, pp. 10). Alignment supports individuals and team performance to be consistent with project objectives and needs. 6. Well-defined organizational structure From project conception and throughout project development, all project parties and members should have a clear and proper understanding of the authority, responsibility, and accountability of each position. The construction manager needs to clearly define project participant s 13

functions and expected performance in order to reduce the potential delays caused by the lack of understanding on who is responsible for what (CII: The Game Planner 2004). 7. Pareto s law management Also known as the 80/20 rule, Pareto s law management rule suggests that attention should be given to the few activities and elements (20%) that represent the major part of the work or benefit (80%). Therefore, the construction manager should focus the attention of the project team in the activities that represent overall project duration. CII affirms that on average around 20 percent of project activities represent 80 percent of overall project schedule duration (CII: The Project Manager s Playbook 2004). 8. Employee involvement Employee involvement can be defined in terms of team building, training, communication, performance appraisal, and rewards. These factors are the key to achieve employee successful self-direction and process improvement (CII: The Game Planner 2004). 9. Realistic scheduling Realistic scheduling is the action of constantly reviewing and updating the overall schedule to reflect real progress and actual situations of the project. Realistic scheduling involves the use of general schedules for overall control as opposed to detailed schedules which are more efficiently used for short-term planning (CII: The Game Planner 2004). 10. Construction-driven scheduling The use of a construction-driven schedule is also an alternative for time management and control as it serves as a baseline for determining how much and when schedule reductions can be achieved. Scheduling software can be very useful in preparing and tracking the schedule (CII: The Project Manager s Playbook 2004). 11. Concurrent evaluation of alternatives Concurrent evaluation of technical alternatives generates important savings in time (CII: The Project Manager s Playbook 2004). 12. Avoid scope definition shortcuts Good scope definition is crucial for project success, particularly when striving to reduce project delivery time. Consequently, it is not recommended to take shortcuts on project scope in an attempt to save time (CII: The Project Manager s Playbook 2004). 13. Use of electronic media The use of electronic media through computer technologies facilitates and improves information management by expediting information delivery, improving data management, encouraging strong communication and promoting project documentation, which finally leads to increased productivity and shorter delivery times (CII: The Game Planner 2004). 14

14. Constructability The CII defines constructability as the optimum use of construction knowledge and experience in planning, design, procurement, and field operations to achieve overall project objectives (CII: The Project Manager s Playbook 2004, pp. 10). Implementing a constructability program at early stages and following during project development can lead to reduced construction duration, ultimately reducing project delivery time. Constructability is further discussed in the following section. 15. Freezing of project scope Project scope should be completed and frozen as early as possible in the planning and design phase such that all the major requirements and decisions are early made. Early freezing of project scope allows addressing important issues that may affect project schedule in an early manner, increasing the potential for project schedule reduction (CII: The Project Manager s Playbook 2004). This technique is discussed in detail in the following section. 16. Reusable engineering Design delivery time can be reduced by reusing design elements from previous projects or from standard design libraries when available. Examples of reusable engineering can be design elements like structural steel connection details or instrument junction boxes, supplier s standard designs for equipment or materials, particular systems such as air compressors, among others (CII: The Project Manager s Playbook 2004). Standard design elements can also be produced and saved to be used several times in the same project. 17. Non-traditional drawing release This technique involves the release of partially completed drawings that contain complete and approved detail to be used for expediting procurement and construction planning. This procedure helps guaranteeing that material and equipment will be available when needed, minimizing delays caused by material or equipment unavailability, thus improving construction timely performance. Similar techniques related to drawing release will be discussed in more detail in following sections (CII: The Game Planner 2004). 18. Supplier/engineer early interaction Obtaining in advance engineering information related to design components that allow followon engineering work enable a faster development of design. If it is necessary, the construction manager should send staff to visit the supplier s shop and obtain key engineering information in advance (CII: The Project Manager s Playbook 2004). 19. Materials management Materials management refers to the efficient planning and controlling of all the actions required to guarantee that materials and equipment are appropriately delivered in terms of quality and quantity in a timely manner at the places needed (CII: The Game Planner 2004). Adequate material and equipment availability is indispensable to allow construction progress. Unavailability of material and equipment are a major source for delays. 15

20. Material coordination The CII recommends delegating staff with the primary or exclusive function of coordinating and managing material at the jobsite. This person should be responsible for maintaining material status and reports to allow connection between field and procurement personnel. In addition, this individual could provide with useful advice in the coordination and management of material during weekly look-ahead planning meetings to assure material and equipment availability when required (CII: The Game Planner 2004). 21. Prioritize procurement of material It is important to establish priorities related to the procurement of important equipment and materials according to the needs of the project but also considering supplier capabilities to make sure that the right items are delivered at the right time and in the right place. Sometimes, coordination of material procurement is improved by having the prime contractor or CM at risk purchasing materials for subcontractors (CII: The Game Planner 2004). 22. Efficient packaging for transportation Typically, the handling and transportation of oversized elements and components of construction involve increased costs and longer delivery times. Considering dimensional limitations of the available or of common means of transportation including length, width, height, volume and weight, during design can help in eliminating or minimizing the need for special transportation and handling (CII: The Game Planner 2004). 23. Material I.D. on purchase documentation The use of a material identification code system can improve the management of materials. When possible, it should be requested to suppliers to provide materials with tags containing identification codes that match purchase orders as well as the working package for which each item or material is intended. This technique facilitates a better on-site control and routing of material, minimizing material misplacement or losses. This technique is only applicable to engineering or tagged items, not to bulk items (CII: The Game Planner 2004). 24. Testing/inspection It is recommended to perform material and equipment inspection at fabricator s or supplier s shop prior to shipping to minimize testing on site. Deficiencies are also easier to correct in the shop rather than after delivered (CII: The Project Manager s Playbook 2004). 25. Multiple suppliers Suppliers may have problems accomplishing delivery dates when orders are too large. It is therefore recommended to use multiple suppliers with smaller orders, however too many suppliers may be difficult to track and coordinate (CII: The Project Manager s playbook 2004). 16

26. Supplier submittal control On-time deliveries from suppliers are a vital factor to assure prompt construction delivery times. To achieve this, the construction manager should develop strict compliance policies regarding supply dates, submittals and approvals of documents, and shop drawings (CII: The Game Planner 2004). 27. Field management Construction processes and schedules can be dramatically accelerated while improved by providing sufficient resources and staff with the sole responsibility of performing field management operations (CII: The Project Manager s Playbook 2004). 28. Safety in workspace Importance consideration should be given to planning for safety which can be achieved by orientations on safety and training. Incentive techniques can also be effective in promoting a safety environment for work. Safety improves workers moral and motivation, improves labor performance and increases productivity, all of these resulting in potential schedule reductions. On the other hand, reduced safety increases the likelihood of accidents, which are disruptive and commonly result in delays (CII: The Game Planner 2004). 29. Aggressive project close-out Project closing-out should be managed as aggressively as the rest of the project. Developing a comprehensive list of the items that remain to be completed and a plan on how to complete them can help in accelerating project delivery and close-out (CII: The Project Manager s Playbook 2004). 30. Detailed plan The development of a detailed plan facilitates the transition to facility operations. The plan should include procedures, training, certification of operators, and a preventative maintenance program if required. Accounting for these minimizes transition delays and expedites facility start-up (CII: The Project Manager s Playbook 2004). 31. Determine system testing requirements Determining in advance which systems require testing is important to assure correct functioning and to eliminate unnecessary testing (CII: The Project Manager s Playbook 2004). 32. Zero accident techniques Safety is fundamental in project close-out and operations start-up. Planning for safety during transition to operations should be carried out to minimize potential accidents and injuries. Again, orientation and training on operations start-up as well as incentive programs enable productivity and better performance. Accidents even in the start-up stage of the project can result into unexpected delays in the delivery of the facility to the owner (CII: The Game Planner 2004). 17

B. Freezing of Project scope a. Technique Freezing of scope is a schedule reduction technique defined as the systematic approach to the early identification of major decisions and requirements that may affect the project delivery time (CII: An Investigation of Schedule Reduction Techniques 1996, pp. 106). It also focuses attention on scope issues and details that are often omitted, forgotten, or left to be addressed at later dates. Identification and scoping of such issues can impact the project delivery time significantly. b. Implementation Early freezing project scope aims at defining the project scope before commencement of detailed engineering. Ideally, early freezing project scopes requires the owner to waive the right to make scope changes after the owner, construction manager and architect/engineer team have defined the project scope, unless these changes are in benefit of the project in terms of cost and schedule. It is recommended too that a date for freezing the project scope should be established and included in the overall project schedule as a milestone. The scope should be completed such that all requirements are defined and major decisions made. Strong attention should be given to details early because addressing them at later stages do not allow for reducing project delivery time. The Construction Industry Institute (CII) recommends following a number of strategies for early freezing of project scope and achievement of radical reduction in project cycle time (CII: The Project s Manager Playbook 2004): o Establish a date to freeze project scope. This motivates the project team to early define requirements and make decisions. o Identify which deliverables will define the baseline. o Perform all relevant reviews prior to scope freeze to add to the quality of scope definition and to minimize potential changes if the reviews were performed after scope freeze. Reviews can include constructability, environmental/health/safety, maintainability, operability/reliability, process simplification and value engineering. o Review to ensure that there is clear alignment of the project scope to the business goals and objectives prior to freezing the scope. o If feasible, ask a contractor to review scope documents for clarity and completeness. This may include documents that a contractor typically would not review. o Freeze portions of the total scope so that these portions can continue moving forward while other portions of the scope are being developed. o Perform an integrated project team review of the scope to ensure completeness and alignment. Companies that have experienced major costs and time saving through early freezing of project scope have adopted a series of common actions. Developing a work plan at the beginning stages of the project that highlights the project s objectives, limitations, and deliverables is one technique frequently adopted. The mission and 18

the details of the work plan are then communicated to the end-users and their feedback is requested to identify aspects related to detailed use, operation, maintenance, etc. that might have been overlooked by the executive team (CII: An Investigation of Schedule Reduction Techniques 1996). When receiving feedback of the project s objectives and work plan, the handling and interpretation of such information is very important. End-users do not always have the required knowledge to understand all the information provided to them. It is also important to identify their needs from their wants. Having someone from the end-users background to participate in the exercise of developing the work plan can be very helpful. The construction manager can then use the feedback to review the work plan and the project s objectives, limitations, and deliverables, along with the owner and architect/engineer to convey the user s needs. This process engages end-users in the decision making process as needed. Detailed milestone schedules can also be developed in the early stages of the project, identifying major tasks, dates and parties involved. All participants involved should be made aware of the developed schedules from its conception so to obtain their commitment to meet the established dates. Buy-in of all participants can also be achieved by involving them in the development of the milestone schedule. Pre-qualifying vendors and suppliers, and establishing policies for handling substitutions also commit them to deliver their part of the work as programmed, decreasing changes and delays. The project mission and work plan should be revised continually by the team and end-users to stay focused on the planned objectives, limitations and deliverables. c. Advantages Early freezing project scope has the potential of reducing project delivery time as major issues that impact considerably the project schedule are considered from the beginning. Early freezing of the project scope can also result in fewer do overs which equal fewer change orders, and reducing change orders also reduces disputes between owner and contractor (CII: An Investigation of Schedule Reduction Techniques 1996). In addition, early freezing the project scope allows improved customer satisfaction and the development of partnering relationships with major customers. Focusing early attention on scope issues and details that are often omitted, forgotten or left to be addressed at later dates enable a more effective planning and improved use of capital. Implementing strategies for early freezing project scope enhances commitment of the team involved, and commitment drives the team to perform towards project success. d. Key elements to ensure a high degree of success Success factors can be categorized in three different areas: employee related issues, management related issues, and process related issues (CII: An Investigation of Schedule Reduction Techniques 1996). 19

Employee related factors o Technical skills of individuals have a very important impact in the success of early freezing of scope to reduce delivery time. o Team dynamics and experience of key team members are also major determinants of success as well as people skills and commitment to success. o High levels of trust between the owner, designer and contractor teams drive to a smoother implementation of this technique. Management related factors o Support from management and team empowerment motivates team members to achieve results. o Management willingness to accept the results of taking risks is an important enabler. o Investment in appropriate training can offer significant pay-offs. o Management needs to develop a high trusting environment and offer direct and visible support. Process related factors o Early involvement of end-users in the process allows an early identification of major project requirements. o The use of information technology is a very helpful tool to establish communication with end-users. o Process continuity is also an essential enabler of freezing scoping success. e. Disadvantages Research carried out by the CII identifies several barriers that regularly hinder the implementation of early freezing scope as a technique to reduce overall project duration. These barriers can be categorized as employee related, management related and process related. Employee related barriers o Lack of skills and training Management related barriers o Lack of budget Process related barriers o Lack of continuity and frequent interruption o Lack of identifying optimum degree of end-user involvement o Lack of determining cost-benefits ratio o Lack of process understanding 20

f. Applicability and use In reality, it is rarely possible to identify all major decisions and requirements and to freeze the scope of a project with such anticipation without forgetting, overlooking or omitting important issues. In addition, the nature of construction and today s competitive businesses environment make it impossible to have no changes once project execution has started. Nonetheless, implementing the actions suggested by this technique allows the owner, construction manager and all parties involved in project development to consider and address major issues and requirements that affect delivery time in early stages. It has been vastly proved that the biggest opportunities for achieving dramatic reductions in project delivery time occur at the early stages and early freezing of project scope increases its likelihood. 21

C. Constructability review a. Technique The CII defines constructability as the optimum use of construction knowledge and experience in planning, design, procurement, and field operations to achieve overall project objectives (CII: Preview of Constructability Implementation 1993, pp. 1). Maximum benefits can be obtained when people with construction knowledge and experience become involved in the early stages of the project. As a general overview, constructability involves a series of steps to determine more efficient construction methods after field forces have mobilized. This can be realized by allowing construction personnel to frequently review engineering documents during the design phase, assigning construction personnel to the engineering office during design progression, and through the development of a modularization or preassembly program (CII: Preview of Constructability Implementation 1993). These activities are an essential part of a constructability effort but the truly effects of constructability can only be achieved through the effective and timely integration of construction input into planning, design, and field operations. Furthermore, the earlier the implementation of constructability in the delivery process, the higher the potential benefits for cost and time savings. Therefore, the constructability process has to start with the owner s conception of the project, and continue through project planning, design, construction, and start-up (figure 1). High Ability to influence cost Planning Design Procurement Construction Low Start-up Start Time Complete Figure 1. Ability to influence the final cost over the life of the project (taken form CII: Preview of Constructability Implementation 1993, pp. 1) 22

b. Implementation The CII has developed a program aimed at providing the construction industry with a tool to be used as a guide in the planning, development and implementation of constructability in construction projects (CII: Constructability Implementation Guide 1993). This process of constructability implementation consists of three major steps: o Obtaining constructability capabilities o Planning constructability implementation, and o Implementing constructability 1. Obtaining constructability capabilities Obtaining constructability capabilities involves acquiring and engaging qualified construction personnel in major management and technical decisions that meet both design and construction needs, and retaining key personnel throughout the life cycle of the project. The first step on implementing a constructability program is to define constructability objectives and measures. Developing a clear understanding of the project s objectives and priorities is essential in guiding people s efforts towards the goal, project delivery time reduction in this case. Once objectives have been identified, all participants in the process should be made aware of them. Establishing project planning duration, design duration, construction duration and start-up duration can be adopted as the general objectives of the constructability application. However, the definition of more specific objectives leads to increased team support and commitment through the implementation of the constructability program. The following are examples of specific objectives cited from the CII s Constructability Implementation Guide (1993, pp. 37): - Use of standardized elements - Use of modules/preassembly - Use of lift equipment - Material laydown areas - Ease of fabrication and erection - Number of field welds - Jobsite accessibility - Develop construction-friendly specifications - Improve constructor/engineer communications - Minimizing construction rework - Minimizing design rework - Minimizing jobsite congestion - Minimizing occurrence of labor disputes After the construction management along with the project team has identified the goals and objective of the constructability program, the next step is to establish how these can be objectively measured. Adopting appropriate measures is important for evaluating the effectiveness of the constructability intention in project schedule performance. Examples of performance measures are labor productivity, number of items nonconforming with owner s specifications, design rework work-hours, number of change orders, lost-time incident rate, shut- 23

down duration (hours), personnel and material jobsite accessibility (feet/hour/unit), etc (CII: Constructability Implementation Guide 1993). An assessment of the owner s available in-house capabilities should be carried out at this point. The procurement of external design and construction constructability expertise might need to be considered too. Decisions will depend on different factor including owner s objectives, availability of resources, project characteristics such as project complexity, project size, project location, construction type, contract type, technical difficulty, among others. The owner s selection of the contracting strategy has also considerable impact in the means and the extent of early construction input in the project. In the traditional design-bid-build or the multiple prime contracting approaches, it is not possible to bring the actual constructor to participate in the planning and design phases. Consequently, under these delivery methods the use of construction knowledge and expertise from outside should be considered. This input may come from the design team or an external consultant with the required expertise. However, construction input from external resources may not be as effective as input from the actual constructor. Conversely, under the design-build contracting strategy, constructability is better implemented because there is one design-build contractor who is naturally encouraged to use constructability in the design phase. Yet, it is important to keep in mind that constructability applied at the early stages of planning, before the design phase, increases potential schedule benefits. As a result, executing constructability under each project delivery technique will have different results due to the timing at which the constructor expertise is available to the project. After defining where constructability input will be obtained from, the next step is to determine how to facilitate an early implementation. When constructability is implemented through external resources, a surrogate construction contractor can provide the necessary construction knowledge and expertise. When the delivery system allows the early involvement of the constructor or requires external resources, a constructability program can be included as part of the prequalification process to guarantee constructor s experience and early commitment to use constructability. The use of incentives is an option to enhance constructability performance. Incentives can be related to specific milestones and completion of specific stages. The benefit of incentive programs increases when incentives are effectively integrated between the design and constructor players. 2. Planning constructability implementation Planning constructability implementation should begin as early as possible and be integrated into the entire project execution plan. It should also include all major project participants to the maximum possible extent. The development of the constructability implementation plan follows three basic steps (CII: Constructability Implementation Guide 1993): 1) Creating the constructability team, 2) Identifying and address project barriers, and 3) Developing constructability procedures and integrating into project activities. Creating the constructability team The constructability team should include as a minimum participants that represent the owner, designer and constructor teams. However, to increase effectiveness of the program, it is also recommended to include representatives from subcontractors, vendors and consultants when 24

applicable. The members selected to participate in the constructability team should have construction experience and knowledge, but also strong interpersonal skills to be able to cooperate with the team and act as team players. Team members must understand the importance of constructability and the desired outcomes of its adoption. The construction manager should also enforce a clear understanding of each individual s specific roles and responsibilities as members of the constructability team. A coordinator should be selected with appropriate experience and skills to manage the execution of the program. Identifying and addressing project barriers Constructability implementation commonly presents several barriers that make its execution more difficult. Some are related to owner s and participants commitment, such as lack of constructability awareness, reluctance to provide funding or invest resources; and other barriers are more specifically related to team members performance or lack of performance thereof, such as complacency with the status quo, lack of construction experience, lack of designer s willingness to adopt constructor s input, adverse relationships between design and constructors, construction input requested or provided too late to be of value, etc. The last section of this section presents a list of the most common barriers identified by the CII in the implementation of constructability. Identification of the potential barriers enables the team to anticipate and be prepared to overcome those shortcomings. Developing constructability procedures and integrating into project activities The development of constructability procedures will depend on the individual circumstances of the project. However, the CII (CII: The Project s Manager Playbook 2005, CII: Constructability - A Primer 1986) establishes seven basic constructability concepts that are generally applicable to the design and procurement phases of any project. o Design and procurement schedules should be construction-driven. o Designs have to be configured to enable efficient construction. o Designs should consider major construction methods when establishing basic design approaches. o Design elements need to be as standardized as possible. o Construction efficiency should be considered in specification development. o Module/preassembly designs need to be prepared to facilitate fabrication, transport, and installation. o Designs must promote construction accessibility of personnel, material, and equipments. o Designs should facilitate construction under adverse weather conditions. o Flexibility in designs and specifications should be provided to allow construction to determine the appropriate means and methods of installation. o All of the appropriate information needed by construction should be contained on drawings or specifications or by reference. o Dual-purpose designs should be considered. These are components that can serve a function in construction as well as commercial operations. Constructability procedures and activities should be developed and integrated with the project schedule. These procedures may include developing a schedule with the timing for the various constructability studies and design inputs, developing schedules for regular meetings to discuss constructability concepts, share lessons learned, and provide constructability input to design. Constructability procedures should also embrace how decisions related to trade-off analysis will 25

be done, and how the constructability program progress will be monitored (CII: Constructability - A Primer 1986). Finally, the constructability activities should be integrated into the project activities. One way to do this is by identifying the what, when and who portions of the process in the constructability schedule and linking these to the project schedule. 3. Implementing constructability Adequate implementation of constructability involves (CII: Construtability - A Primer 1986): 1) applying constructability concepts and procedures, and 2) monitoring and evaluating project program effectiveness Applying constructability concepts and procedures Constructability concepts are nothing more that lessons learned from past projects that have spread out within the construction industry. CII and other organizations have extensive checklists of general constructability concepts that can be applied in any given project. However, developing more specific concepts from individual experience and lessons learned improves the quality of constructability input during planning and design. Constructability procedures are actions that have to be implemented by each team member throughout the design phase in order to generate construction input in design. Thus, each member should follow procedures based on its role and responsibilities. Monitoring and evaluating project program effectiveness The team coordinator should monitor constructability progress in order to measure its effectiveness and take corrective actions when needed. When the program is failing in meeting constructability objectives, the coordinator can turn to the list of barriers identified in previous steps to find possible areas of failure. One common weakness in the process is poor communication and deficient working relationships among team members. After obstacles and difficulties have been identified, actions should be adopted to address these. Sometimes it is also necessary to modify constructability procedures or activities to overcome barriers. c. Advantages An appropriate and successful application of constructability in the early stages of project development provides with the following potential benefits (CII: Constructability Implementation Guide 1993, CII: Constructability - A Primer 1986): o Significant schedule improvements o Earlier project completion o Significant reductions in overall installed project expenses, being construction savings the major factor in reducing expenses o Improvement in project quality, for the most part design and construction quality o Better productivity o Improvement of safety during construction o Savings in project costs while preserving aesthetics 26

d. Key elements to ensure a high degree of success One of the major determinants of the success of constructability is the timing at which it is introduced. Hence, in order to explode its potential benefits to its maximum, constructability has to be implemented at the earliest stages when the project is conceptualizing, and continue through project planning, design, construction, and start-up. The construction manager has a critical influence on the success of the project s constructability implementation. When all the team members are truly committed since constructability planning, the chances of attaining greatest benefits increase. Therefore, construction manager s efforts must focus on enhancing commitment from team members to establish a supportive environment and assure constructability success. Commitment however should not be merely directed implementation of the program itself but also to the results in terms of time expected from program s implementation. Constructability can be enhanced when the influence it has over delivery time is emphasized and clearly understood by all parties involved. The owner s selection of the contracting strategy has also substantial impact in the means and the degree to which early construction input into project planning and design can be achieved. Establishing the appropriate project delivery technique will therefore contribute to a successful application of constructability reviews. Regardless of the source from which constructability input will be obtained, a constructability program can be included as part of the prequalification process to guarantee constructor s experience on constructability and early commitment to the program. This can be applicable to situations in which the actual constructor is involved early in project planning and design, or when external resources or consultants are required. The use of incentives has the potential of enhancing constructability performance when incentives are effectively integrated between the design and constructor or constructability teams. The development of common goals among team members is also a key to developing joint-work to achieve constructability success. When selecting members to make the constructability team, several aspects need to be taken in consideration to enhance team effectiveness. First, it is essential to compose a team of individuals with extensive experience and knowledge. It may be worth to develop selection criteria in advance to obtain the minimum level of expertise. Nonetheless, it is also important to select team players that are willing to cooperate, work in team, and accept other participant s points of views. An environment of open communication supports the development of a cohesive team with joined objectives which increases thereby commitment to the program. Finally, the importance of continuity within the team is fundamental to achieve success; team turn-over must be minimized. Developing a constructability program based on a forward-looking, integrated planning philosophy instead of a backward-looking review of completed design increases the quality of design and decreases the risk of design rework. Developing a schedule which determines the needed time of constructability studies and design inputs allows for a smoother adaptability to the process. Regular meetings of the constructability team enable discussing concepts, sharing lessons learned, and providing constructability input to design. An appropriate strategy to improve the 27

efficiency of constructability reviews is to perform a final review for completeness and accuracy of design details on design packages that are ready to be submitted. This approach can prevent rework when changes in design occurred after initial constructability review. One way to monitor and evaluate constructability outcomes is by maintaining communication with the contractor throughout the construction phase of the project. Evaluations also allow discovering areas of possible improvement in the next stages of the constructability program. e. Disadvantages Coordination of the different parties is a major issue when adopting constructability. If the team is not well managed and coordinated the introduction of other parties into the design stage of the project can result in adverse relationships hindering project success. f. Applicability and use Extensive case studies have demonstrated that constructability applications are investments that result in substantial returns in terms of project quality, costs and time. The technique presented herein provides owners, construction managers and other applicable parties with the basic steps to successfully implement a constructability plan to improve construction performance and reduce delivery times. The more detailed and more time and effort devoted to implementing constructability the greater the likelihood of project success. However, taking into account basic constructability concepts during project design can improve construction performance (CII: The Project s Manager Playbook 2004, CII: Constructability - A Primer 1986). The following are a few of these key concepts: o Design and procurement schedules should be construction-driven. o Designs have to be configured to enable efficient construction. o Designs should consider major construction methods when establishing basic design approaches. o Design elements need to be as standardized as possible. o Construction efficiency should be considered in specification development. o Module/preassembly designs need to be prepared to facilitate fabrication, transport, and installation. o Designs must promote construction accessibility of personnel, material, and equipments. o Designs should facilitate construction under adverse weather conditions. o Flexibility in designs and specifications should be provided to allow construction to determine the appropriate means and methods of installation. o All of the appropriate information needed by construction should be contained on drawings or specifications or by reference. o Dual-purpose designs should be considered. These are components that can serve a function in construction as well as commercial operations. g. Other special characteristics For a constructability program to be effectively implemented, potential barriers should be identified and defeated. CII provides a list of typical barriers encountered in the implementation of constructability programs (CII: Constructability - A Primer 1986). The use of barriers checklists can assist team participants in assessing whether a particular barrier is significant and needs more attention and effort to be addressed and overcome. The checklist can also be used 28

periodically to evaluate if identified barriers are being correctly addressed or still need to be mitigated, and to identify and defeat new barriers that can appear along with the implementation of constructability. Some barriers are related to the owner, others the designers or contractors, and some affect all the parties involved in the project. The following are barriers checklists that affect a particular party or all of them at the corporate level and at the project level (CII: Constructability Implementation Guide 1993): Constructability barriers checklist applicable at the owner corporate level Complacency with the status quo o resistance to change o conservative, non-innovative approaches o risk-averse attitudes towards trying something new o no rewards for intelligent risk-taking o a not invented here syndrome Lack of documentation and retrieval of lessons learned o no formal system for documenting lessons learned o reliance on word-of-mouth and experienced personnel to transfer innovative ideas Lack of awareness/understanding of the concepts of constructability, no procedural roadmap is available o constructability used as a buzzword o efforts ineffective due to lack of coordination; direction Perceptions that we do it o routine design practices fully exploit constructability o we already pay for it o we do value engineering; value engineering equals constructability There are no proven benefits of constructability o too expensive o senior management is not convinced of the cost-benefits Reluctance to invest additional money, effort, and time in early project stages o inability to acquire additional front-end funding o inflexible design fee structure/inflexible scope of design services o expectation of free advice/consulting form contractors and consultants Lack of genuine commitment to constructability o constructability is low priority o no policy statement exists, no champion o there are higher priorities 29

Constructability barriers checklist applicable at the designer corporate level Complacency with the status quo o resistance to change o conservative, non-innovative approaches o risk-averse attitudes towards trying something new o no rewards for intelligent risk-taking o a not invented here syndrome Lack of documentation and retrieval of lessons learned o no formal system for documenting lessons learned o reliance on word-of-mouth and experienced personnel to transfer innovative ideas Perception that we do it ; very narrow view of constructability Lack of awareness/understanding of the constructability concepts and/or benefits o constructability used as a buzzword o efforts ineffective due to lack of coordination; direction Lack of construction experience/qualified personnel Lack of mutual respect between designers and constructors o resentment of outsiders o pride of authorship Contractor or construction input is requested too late to be of value o belief design personnel can provide construction input during early stages o reluctance to allow construction into review processes Constructability barriers checklist applicable at the EPC (Engineer-procur-construct) corporate level General organization barriers Complacency with the status quo o resistance to change o conservative, non-innovative approaches o risk-averse attitudes towards trying something new o no rewards for intelligent risk-taking o a not invented here syndrome Lack of documentation and retrieval of lessons learned o no formal system for documenting lessons learned o reliance on word-of-mouth and experienced personnel to transfer innovative ideas 30

Designer barriers Perception that we do it ; very narrow view of constructability Lack of awareness/understanding of the constructability concepts and/or benefits o constructability used as a buzzword o efforts ineffective due to lack of coordination; direction Lack of construction experience/qualified personnel Lack of mutual respect between designers and constructors o resentment of outsiders o pride of authorship Contractor or construction input is requested too late to be of value o belief design personnel can provide construction input during early stages o reluctance to allow construction into review processes Constructor barriers Poor coordination skills; design criticism is often non-constructive or communicate in an offensive, tactless manner Constructability barriers checklist applicable at the constructor corporate level Complacency with the status quo o resistance to change o conservative, non-innovative approaches o risk-averse attitudes towards trying something new o no rewards for intelligent risk-taking o a not invented here syndrome Lack of documentation and retrieval of lessons learned o no formal system for documenting lessons learned o reliance on word-of-mouth and experienced personnel to transfer innovative ideas Poor coordination skills; design criticism is often non-constructive or communicate in an offensive, tactless manner Constructability barriers checklist applicable at the project level General project barriers Complacency with the status quo o resistance to change o conservative, non-innovative approaches o risk-averse attitudes towards trying something new o no rewards for intelligent risk-taking o a not invented here syndrome 31

The right people were/are not available Owner project barriers Lack of awareness/understanding of the concepts of constructability; no procedural roadmap is available o constructability used as a buzzword o efforts ineffective due to lack of coordination; direction Perceptions that we do it o routine design practices fully exploit constructability o we already pay for it o we do value engineering; value engineering equals constructability Lack of team-building or partnering o client-contractor relationships/communications are not respected and nurtured o adversarial relationships are free to develop (expected, accepted, and perhaps even subconsciously promoted) Misdirected design objectives and designer performance measures o mentality is design-driven vs. construction-driven o design process is design-cost driven o design process is design-schedule driven Use of lump-sum competitive contracting, leading to: o limited opportunity for involvement of construction contractor up-front o a false sense of economy with a low bid with constructability viewed as an accessory o requirement for complete plans and specs, precluding a fast-track approach o adversarial relationships on changes o not wanting to give a competitive advantage to reviewers Reluctance to invest additional money, effort, and time in early project stages o inability to acquire additional front-end funding o inflexible design fee structure/inflexible scope of design services o expectation of free advice/consulting form contractors and consultants Designer project barriers Perceptions that we do it ; very narrow view of constructability Lack of awareness/understanding of the constructability concepts and/or benefits o constructability used as a buzzword o efforts ineffective due to lack of coordination; direction Lack of construction experience/qualified personnel Lack of mutual respect between designers and constructors o resentment of outsiders o pride of authorship 32

Contractor or construction input is requested too late to be of value o belief design personnel can provide construction input during early stages o reluctance to allow construction into review processes Constructor project barriers Poor timeliness of input Poor coordination skills; design criticism is often non-constructive or communicate in an offensive, tactless manner 33

D. Cycle time analysis a. Technique Cycle time is defined as the duration for accomplishing a preestablished set of activities; therefore cycle time analysis (CTA) is the formal process of cycle time review to ensure delivery of exactly what is needed, when it is needed, and the amount needed, while eliminating unnecessary activities from all functions of an organization (CII: Schedule Reduction 1995, pp. 18). Applied to the construction industry, cycle time analysis is the systematic process of examining each and every step in the process of delivering a project with the objective of eliminating activities and events that add no value to the project aiming at achieving overall project schedule reduction (CII: An Investigation of Schedule Reduction techniques 1996). b. Implementation Cycle time analysis has been mostly applied to project construction to remove non-value adding activities in construction processes; nonetheless, the same principles that guide cycle time analysis during construction can be applied to any phase of the project. Thus, cycle time analysis applied to planning, design, construction and start-up can lead to reduced delivery schedules by eliminating those processes that add no value to the project. There is no recorded formal procedure for implementing cycle time analysis; however, based on extensive research in combination with case studies, the CII provides the industry with a set of implementation guidelines (CII: Schedule Reduction 1995): o Form a cross-functional steering team with representation of key stakeholders under the leadership of the project or construction manager. o Select a target process or focus area for the analysis. Examples of target processes can be inventory reduction, routing and approval procedures of paperwork, just-in-time manufacturing, minimizing equipment downtime, innovative construction sequences, and so on. o Form teams around the selected work areas. For construction cycle time analysis teams should be developed at the worker level around the selected work areas. Use facilitators and provide the teams with training in team dynamics and techniques specific to the focus area, for example, statistical techniques and just-in-time management. o Map the overall work processes with the use of flowcharts and identify problem areas. Problem areas may include redundant and unnecessary steps, inconsistent handling of the same task, same information regenerated at different stages for different purposes by different groups, lack of uniformity on repetitive processes, excessive waiting times, etc. Work teams can help in identifying specific issues within their work areas. o Select performance indicators, execute measurements, and chart and post the process and results in each work area (e.g., productivity yields, delivery schedule, absenteeism, cost of poor quality and throughput time, etc). o Communicate the goals and progress of the analysis to the employees involved with the process, and provide them with necessary retraining. o Use technology to provide common databases and automate information transfer and transactional type activity. 34

c. Advantages Cycle time analysis implementation has great potential of reducing project delivery time considerably, while implementation costs are minimal compared to overall installed project costs and the achievable time savings. In addition to reducing overall project schedule, other benefits that can be achieved with cycle time analysis include reduction in operating capital and identification of bottlenecks. Cycle time analysis also enhances employees sense of ownership, augments productivity, leading to increased job satisfaction. All these gains generated by this technique ultimately translate into reduction of total project cost. The application of cycle time analysis through the formation of teams is important as it considers input and recommendations from individuals actually involved in the process under study for compression. This approach triggers employees motivation and enhances commitment to accomplish schedule reductions. Involvement and input from team members also enable consensus to be formed considering not only the priorities of the project but also the priorities of the team, which encourages adherence to the cycle time program. Consensus also promotes an environment of work team which is always fundamental for achieving common goals. One last benefit of employing cycle time analysis is that it enables the identification of hidden problems in disciplines other than time and schedule related. Analysis and involvement of employees in work processes also encourage innovation. d. Key elements to ensure a high degree of success There are several important factors that contribute to the success of implementing cycle time analysis (CII: Schedule Reduction 1995): o Commitment and support of top management. o Strong and open communication at all levels of the project, particularly when approaching problem resolution to avoid adversarial consequences. o Training of employees in cycle time analysis and problem-solving techniques. Lack of a structured approach leads to ineffective cycle time analysis and eventual loss of employee interest. o Open communication and support to employees. Employees need to feel comfortable with the process to be willing to recognize and resolve problems, particularly when identifying bottlenecks, without the fear of job loss. Cycle time analysis results can be improved if its implementation is combined with other schedule reduction techniques such as constructability and concurrent engineering. e. Disadvantages One particular disadvantage of cycle time analysis is that, to be effective, it requires constant guidance from management to keep the team focused on the objectives of the technique s application. Cycle time analysis requires team participants to carry out the functions they usually perform to achieve project progress but, in addition, to devote time and effort in following and analyzing processes to recognize wasteful activities that add no value. Consequently, if adequate guidance and awareness is not constantly provided to team participants, these tend to easily 35

loose focus on objectives hindering successful results from analysis of cycle times. Moreover, once the areas of waste have been identified and addressed, constant awareness is required to maintain workers and employees performance aligned with adjusted processes. Participants commitment can also be easily weakened by lack of genuine motivation. Without the appropriate support, employees will unconsciously tend to go back to their work routine in which wasteful activities are allowed. f. Applicability and use Cycle time analysis as an approach to schedule reduction has been successfully applied within the industry. Research proves that this technique can result in dramatic overall cycle time reductions. However, case studies also demonstrate that a strong motivation for improvement and for achieving results is important to commit to the process. The applicability of cycle time analysis highly depends on management commitment and dedication in terms of time and budget, and most importantly, a willingness to implement the findings of the cycle time analysis (CII: Schedule Reduction 1995). To reduce processes durations and therefore project delivery time, this technique can be successfully implemented in any phase of the project individually, or applied to the phases or processes that show greater potential for wasteful areas. Examples of phases that may benefit from cycle time analysis the most are project funding approval, drawing and specification reviews, and material procurement approvals (CII: Schedule Reduction 1995). 36

E. Concurrent Engineering a. Technique The Research Center for Concurrent Engineering defines concurrent engineering as a methodology for developing new products efficiently by designing the product while simultaneously considering all aspects such as manufacture, maintenance and support (CERC 2006, CII: An Investigation of Schedule Reduction Techniques 1996). In the engineering and construction industry, concurrent engineering is a systematic approach to include all entities affecting or affected by the subject project in the planning, engineering, and design of the project (CII: An Investigation of Schedule Reduction Techniques 1996, pp. 34). Having multiple parties involved since the early design of a project enables addressing all angles of a project from project conception and the accumulation of knowledge and information so as to reduce downstream risks and anticipate constructability, operability, and maintainability expectations (de la Garza et al. 1994). Concurrent engineering therefore aims at identifying all project requirements and expectations at the earliest stage possible. Concurrent engineering forces participants from all phases of the project total life cycle including owners, designers, construction managers, constructors, suppliers, operations and maintenance, and end-users, to play an active role from project s conception. The input from different sources at early stages enables to consider all elements of the project life cycle including quality, cost, schedule, and user requirements (CERC 2006). Highest 5 4 Relative contribution 3 2 1 Lowest 0 Pre-planning Design Procurement Construction Start-up Time (Project phase) Figure 2. Impact of concurrent engineering over project life cycle (taken from CII: Schedule Reduction 1995, pp. 13) 37

b. Implementation Concurrent engineering primarily aims at integrating the development of a product, which is achieved by the development of multifunctional or interdisciplinary teams in project s early phases of conception. Project s different phases are thus integrated through the knowledge and early input of the formed team (de la Garza 1994). The team should consist of experts from both upstream and downstream phases of the facility to be built. Traditional project delivery methods entail that certain project activities are completed before the start of subsequent activities to assure that the information required in the downstream tasks is accurate and fully available. It is also commonly required under this delivery approach that the information is reviewed multiple times for approval before being transmitted to succeeding activities. Concurrent engineering, on the other hand, requires end-users and other participants to play an active role in the engineering phase to reduce or eliminate the need of activity review and speed up the beginning of subsequent activities. New approaches to concurrent engineering go further with this theory by starting subsequent tasks earlier before all the required information becomes available leaning on the early involvement of the project team and in ongoing reviews and early decision-making. Fast-track is one such technique that aims at concurrent engineering principles seeking acceleration of project completion. Fast-tracking production recurs to the overlapping of design and construction, thus construction activities corresponding to early stages of a project are performed when later stages are still under design. Other approaches recur to concurrency philosophies specifically applied to the design and construction phases separately. Concurrent engineering applied to design consists of overlapping sequential design activities with the objective of speeding up design delivery, thus reducing overall project delivery time. The same approach is adopted in the construction phase. By overlapping sequential construction activities, the construction schedule can be reduced, leading to reduction in overall project duration. These and other similar techniques will be discussed in detail in later sections. The first step to implement concurrent engineering is to establish the members that will form the design review working group. The team should have representatives from all the disciplines that compose the project scope. The objective of the team is to be present at the design stage to identify internal customers and involve downstream users during the design phase. Emphasis should also be given on obtaining input and involvement of the owner to achieve a strong buy-in to the design. The team is responsible for identifying during conceptual engineering the critical activities that make up project duration in order to center major focus and effort on achieving early completion of these. The team can develop a list of the objectives and improvements expected with the adoption of concurrent engineering practices, thus management should be oriented to meet the objectives. The team may also develop a schedule in order to proceed with the detailed design. A schedule of short-term goals and milestones enhances achieving objectives in a timely manner, and regular meetings can be helpful for monitoring and controlling how the objectives are being conveyed, and to develop new short-term milestones and plans. As the design develops, the team evolves as needed so to provide input with the required level of knowledge and detail. c. Advantages The application of concurrent engineering in the early stages of a project has significant opportunities of improving and shortening overall project duration. If correctly implemented, 38

concurrent engineering allows great potential for reducing design errors due to the input of downstream knowledge. Concurrent engineering practices also minimize the need for excessive drawing revisions, which ultimately leads to shorter design delivery time. The input of different sources in the engineering phase generates an enhanced design that allows for improvement in the subsequent phases of the project including construction and start-up. Additionally, since a higher percentage of the engineering deliverables can be emitted to the field before the completion of all design activities, the construction phase of the project can begin earlier and completed faster. Improved design development also generates fewer changes in design, reduced field rework, reduced project costs, and a better basis for efficient construction planning. Having multiple parties involved at the design of a project enables knowledge and information input which reduces potential risks on downstream phases and enhances constructability, and project operability and maintainability. Moreover, because concurrent engineering is a philosophy product and market-oriented that encourages input of different disciplines including owners and end-users in the design phase, its implementation can also be translated into increased customer satisfaction (CII: An Investigation of Schedule Reduction Techniques 1996). The different applications of concurrent engineering through activity overlapping also bring about potential benefits in the design and construction phases of the project in terms of project delivery time. Finally, concurrent engineer facilitates a more appropriate allocation and share of risk between all parties involved in project s overall life cycle. d. Key elements to ensure a high degree of success To assure and increase the chances of project success, concurrent engineering applications should be adopted at the very inception of project development and continue during the design phase. Concurrent engineering practices throughout construction can also lead to improved operations start-up. Adopting concurrent engineering practices combined with aggressive schedules increases the opportunities for reducing project delivery time. Schedules should be demanding, but yet achievable to encourage the project team to behave under concurrent engineering philosophies (CII: Schedule Reduction 1995). In addition, demanding schedules enhance team s motivation and effort to work toward the schedule goals. However if the schedule is not realistic, the lack of motivation will likely result in poor team s performance, ultimately leading to unfavorable schedules. Concurrent engineering success requires the team to operate as a single unit with focus on issues rather than individuals. Its success depends in common objectives and team work. Team members need to not only have a clear understanding of the goals expected from the implementation of this technique, but also to adopt these as common goals and perform accordingly rather than acting under individual objectives of the group they represent (de la Garza et al. 1994). Communication and collaboration are also key factors for team success. de la Garza et al. define three stages that lead a team to truly collaboration. These stages are: to define a common vocabulary, agree on a common purpose, and agree on individual priorities (de la Garza et al. 39

1994). Adopting these concepts from the inception of the project increases the chances of team success. The capabilities and compatibility of the individuals assigned to the team also have significant impact on the success of the concurrent engineering implementation. Experience and interpersonal skills are important in project participants to interact with each other and achieve collaboration. Team members also need to have communication skills and to be flexible to adopt other participants views. Involvement of open-minded individuals that are willing to support new practices, even though it may mean changing the way they had done things in the past, also increases the likelihood of team success. Finally, team participants should be willing to accept responsibility for making decisions and should take an active role towards common goals. Locating the project team at a common site enhances face-to-face communication. Information technologies are also an important enabler of communication to link all participants. The generation of an appropriate communication infrastructure promotes faster and improved exchange of ideas, processes, and integrated design, and it also supports feedback from endusers (de la Garza et al. 1994). Management support is very important to keep the project in progress as project team members constantly face decision-making based on partial or incomplete data. Decision making requires risk-taker managers, yet, decisions should also be taken prudently. e. Disadvantages Concurrent engineering beliefs support the simultaneous execution of subsequent tasks, where the downstream activity is carried out before the preceding activity has been completed. The decision of beginning subsequent components without the required information is completed introduces potential risks of project changes and rework. Poor planning and lack of prudence can drive to poor decisions based on wrong assumptions, all of which can have negative impacts in project execution leading to rework and delays, and ultimately to increased costs. f. Applicability and use Concurrent engineering principles are effective tools to achieve project delivery time reduction and to improve overall project performance. The greatest potential for project reduction however is for large, complex projects, where input from many sources is a must to develop and implement the project (CII: Schedule Reduction 1995). Major benefits can be obtained from applying concurrent engineering practices in the design phase, nevertheless, opportunities for its use can also be found within project s concept development, procurement, and construction phase (CII: Schedule Reduction 1995). The potential for properly allocation and share of risk that concurrent engineering allows enhances its applicability as a tool to reduce project delivery time (CII: Schedule Reduction 1995). g. Other special characteristics The CII has devoted effort and time in the research of concurrent engineering as a technique for project delivery time reduction. Within its research, the CII identifies a series of common 40

barriers to the successful implementation of concurrent engineering which include (CII: Schedule Reduction 1995): o Management reluctance to delegate authority and responsibility to team members in the decision-making process. o Resistance to integrate suppliers before the design has been completed, which hinders their input into initial designs. o Inadequate training for those who need knowledge in concurrent engineering processes. o Lack of measure to track the impact of concurrent engineering implementation. o Aversion to the risk associated with the decision-making based on partial or incomplete data. o Failure to make proper allowances for changes after decisions have been taken. o Lack of human resources to implement concurrent engineering at the beginning of the design phase. In contrast, the willingness to share risk between owners, construction managers, designers, suppliers, and contractors have contributed to the adoption of concurrent engineering as a tool to reduce project delivery time (CII: Schedule Reduction 1995). 41

F. Overlapping sequential design activities based on concurrent engineering a. Technique Overlapping sequential design activities is a strategy developed based on concurrent engineering principles that allows reducing the time usually required to complete project design. Reducing design delivery time allows construction to start sooner, thus leading to reduction of overall project delivery time. One way to reduce overall project delivery time is by adopting concurrent, overlapped design processes by overlapping dependent activities instead of following traditional sequential processes. Following concurrent engineering practices, overlapping strategies resort to reducing or removing information dependencies among activities by altering their existing characteristics to create a more favorable environment for activity overlapping. The extent to which two activities can be effectively overlapped depends on the relationship between them. Prasad identifies 4 possible types of relationships between activities (Prasad 1996): 1) dependent activities, 2) semi-independent activities, 3) independent activities, and 4) interdependent activities. When two activities are dependent, the downstream activity requires information from the upstream task before the downstream task can begin. Semi-independent activities require only partial information from the upstream activity before the downstream activity can be started. Independent activities require no information from one activity before the other activity can begin. Interdependent activities require a two-way information exchange between them before either can be completed (Prasad 1996). Independent activities can be overlapped without any risk of delay or rework because the upstream activity does not require information from the downstream activity to begin. Dependent activities, on the other hand, carry risk when overlapped. When overlapping dependent activities, the downstream activity begins before all the information from the upstream activity is available, thus, the downstream activity begins with incomplete, nonoptimal, or non-final information (Bogus et al. 2005). Changes in the upstream activity can also impact the downstream task, resulting in potential delays and/or rework. Because of this risk involved in overlapping dependent activities, this technique focuses on developing strategies to reduce the dependencies between these. The degree to which dependent activities can be overlapped is determined by the nature of information exchange between them. The information exchange between an upstream activity and a downstream activity can be described in terms of the natural rate of information evolution in each activity and the sensitivity of the downstream activity to changes in upstream information (Bogus et al. 2005). Thus, activities characteristics of evolution and sensitivity are used to determine appropriate strategies for achieving overlap to reduce design delivery cycles. Information evolution The natural evolution characteristics of an activity determine the rate at which information is generated when no time constraints or pressures are applied. In a traditional design process, work is performed following the natural evolution characteristics of activities; therefore, activities are carried out only when all upstream information is available. However, traditional approaches do not always allow for the most effective design delivery process in terms of time. Hence, evolution characteristics can be used in project scheduling decisions to identify potential opportunities for overlap to reduce design time. 42

According to Bogus et al. s research work, there are four essential determinants of an activity s evolution (Bogus et al. 2005): o Design optimization o Constraint satisfaction o External information exchange o Standardization Design optimization refers to the level of optimization achieved by design elements or the number of design alternatives evaluated. For example activities that require the evaluation of many alternatives will have slower evolutions than those that require only one or a few alternatives. Constraint satisfaction refers to the flexibility of design elements in satisfying constraints such as physical limitations. External information exchange refers to the amount of information received from or reviewed by external sources. Activities that require information from external sources may result in multiple iterations of design. These activities will have a slower evolution than activities that do not require external information exchanges. Standardization describes the level of standardization in the design product and/or the design process. Standardization allows activities to have faster evolutions (Bogus et al. 2005). Information Sensitivity Sensitivity refers to the amount of rework that a downstream activity will have to go through if information on the upstream activity changes. So, a highly sensitive activity will require a larger amount of rework if upstream information changes even when the change is minimal. Bogus et al. define the following as the main determinants of sensitivity in design activities (Bogus et al. 2005): o Constraint sensitive o Input sensitive o Integration sensitive Activity sensitivity can be determined by the proximity of the downstream design to boundaries or constraints. When a downstream design element is near a certain type of constraint, such as a maximum or minimum capacity performance, the changes in upstream information can lead to significant rework in the downstream activity. Input sensitive refers to the level of dependence of downstream tasks on specific inputs from other activities. Integration sensitive involves the ability of downstream design elements to be separated from the entire system (Bogus et al. 2005). b. Implementation Based on activities characteristics of evolution and sensitivity, Krishnan et al. define overlapping in four possible situations (Krishnan et al. 1995). The first one is given when evolution of the upstream task is fast and the sensitivity of the downstream task is low. This is the most convenient situation for overlapping, which is highly recommended through exchange of preliminary design information and early finalization of the upstream design. This strategy is termed distributive overlapping. The second situation is given when activity evolution and sensitivity are both low. Under these circumstances overlapping is recommended only through 43

the exchange of preliminary design information, called iterative overlapping. When evolution is fast but sensitivity high, only early finalization of upstream information is recommended, referred to as preemptive overlapping. Finally, when evolution of the upstream activity is low and sensitivity of the downstream task is high, overlapping should occur to the least degree possible. In this situation, the strategy recommended is to decompose activities into subactivities or packages known as divisive overlapping (Krishnan et al. 1995). Upstream activities with fast evolution and downstream activities with low sensitivity represent the better combination for effective overlapping. Thus, overlapping strategies should aim at changing the evolution upstream activities from its natural state to a faster state to speed up the design process of the activity. Sensitivity characteristics are more likely to be affected by the design situation; in consequence, unlike evolution there are no natural characteristics that determine the sensitivity of downstream tasks to upstream information changes. Once activities characteristics of evolution and sensitivity have being defined and characterized, adequate overlapping strategies can be applied to speed up activities evolution and reduce activities sensitivity. Bogus et al. suggest the following (Bogus et al. 2005): Strategies that speed up evolution Early freezing of design criteria Early freezing of design criteria consists on releasing information from an upstream activity to the downstream activity before the upstream design is complete. This strategy requires project participant s commitment early in the design process to generate the specific required design criteria as soon as possible. Advantages By early freezing design criteria, some of the uncertainty on downstream design is reduced by eliminating the likelihood of changes in upstream information when downstream activities have already begun. Disadvantages Early freezing design can lead to increased project costs due to lack of design optimization. There is also risk that the pre-established criteria may not be feasible in all situations, therefore, the risk of rework in downstream activities that have already begun based on the initial design criteria increases. Design quality and final products may also be affected by the loss of information quality in the upstream activity at the time of freezing. Key elements to ensure a high degree of success Early freezing of design criteria is recommended only when the upstream activity is fast evolving. 44

Early release of preliminary information Early release of preliminary information from the upstream activity also enables the downstream activity to begin before the upstream activity is completed. Advantages This strategy allows downstream activities to begin faster than traditionally based on preliminary information, resulting in potential reduction of overall design delivery time. Disadvantages The risk associated with the early release of preliminary information is that this information might change as the upstream activity is finalized. If changes happen, the downstream activity may require rework, resulting in extra costs and delays. The impact that changes in the upstream design have on downstream activities is directly related to the amount of overlapping between activities; thus, the more the overlap, the greater the impact that upstream design changes have on downstream activities, and the higher the amount of rework. Key elements to ensure a high degree of success This strategy is only recommended when the downstream activity has low sensitivity to changes in upstream information. Prototyping Prototyping is the process of quickly compiling preliminary upstream design information into a working model of the ultimate system (Bogus et al. 2005). This model is a preliminary prototype which serves as a basis for discussion and revision among project designers to produce the final product based on the preliminary prototype. Advantages Prototype models allow the downstream activity to proceed when the working model is finished, before the actual upstream activity is finalized. Prototyping is very suitable for complex systems, where there are many pieces of information to pass to downstream activities. Disadvantages Prototyping is based on early criteria which typically require substantial revisions before the activity can be completed. This introduces a high risk of significant rework on downstream activities and the related costs and delays. Key elements to ensure a high degree of success This strategy is only recommended when the downstream activity has low sensitivity to changes in upstream information. 45

No iteration or optimization This strategy is applied to activities with a naturally slow evolution, where iteration or optimization delays the availability of upstream information to downstream activities. Thus, this overlapping technique recurs to placing time constraints by limiting the number of iterations allowed in an upstream activity before passing the information for downstream design. Advantages Limiting iteration or optimization speeds up the evolution of a slow evolving activity, which allows information to be passed to downstream tasks earlier. Through this strategy, downstream activities start faster to reduce project design cycles. Disadvantages The lack of design optimization introduces substantial risks of significant rework on the downstream activity leading to increases in project costs and potential delays. Key elements to ensure a high degree of success By definition, this strategy is only applicable to upstream activities with a slow evolution. Standardization Standardization refers to the adoption of design practices to be used repetitively on a project (Gibb 2001). This technique aims at the adoption of standardized products, components or designs to accelerate the natural evolution of an upstream activity so information can be released to the downstream activity earlier. Advantages Standardization expedites the transmission of upstream information to the downstream task, reducing design delivery time. If properly applied, standardization may also decrease project costs by eliminating sub-optimal designs (designs in which only one designer has optimized its part) and by increasing constructability (Bogus et al. 2005). Disadvantages Similar to other strategies, standardization involves the risk of project cost increases and delays due to possible rework as a result of lack of design optimization. Key elements to ensure a high degree of success Again, this strategy is only applicable to upstream activities with a slow evolution by definition, as fast evolving activities are already standardized. 46

Strategies that reduce sensitivity Overdesign Overdesign relies on the adoption of conservative assumptions. By making conservative assumptions, it is possible to work in the downstream activity before the upstream activity is completed, and in some cases, before the upstream activity has even begun. Advantages Starting downstream activities before the upstream activity is completed or has begun allows starting activities faster, reducing thus overall design delivery time. Disadvantages The risk involved in overdesigning is that the assumptions made might not be conservative enough leading thus into having to redesign and rework on the downstream activity. Therefore, overdesigning presents the risk of increasing project costs and delays because of rework. Key elements to ensure a high degree of success The extent to which sensitivity is reduced depends on the quality of information used for overdesign in the downstream activity. In consequence, faster evolving activities are, by nature, more likely to provide better information to develop overdesign assumptions for downstream design. Nonetheless, overdesign is also recommended to upstream activities with slow evolution as this strategy based on conservative assumptions for design. However, more risk is taken when applying overdesigning strategies with slow evolving upstream activities. Set-based design This technique refers to the parallel development of multiple upstream designs to decrease the sensitivity of downstream activities. In a set-based design, a designer develops a set of solutions for one component in parallel with designers of other components. As design progresses, the set of solutions are gradually narrowed. However, designers agree to stay within a narrowed predetermined group of solutions; therefore the final design represents a final integrated solution of the individual designs that falls into the pre-established solution set. Advantages Set-based design allows designers to develop downstream design sets at the same time that upstream activities are designing their sets, which reduces the sensitivity of downstream activities to changes in upstream activities. Design delivery time is reduced because downstream design is developed earlier in the process. Disadvantages This strategy presents a major disadvantage. Developing multiple designs for each activity or a more conservative single design increases design costs. 47

Key elements to ensure a high degree of success Set-based design is best applicable when the upstream activity has a slow evolution as the strategy assumes the development of multiple alternative upstream designs. Decomposition This strategy consists on the decomposition of one activity into smaller packages of activities with faster evolution characteristics. Decomposition can also be applied to downstream activities to reduce their sensitivity. The objective of decomposition is to create new activities that can be overlapped using any of the previously mentioned overlapping strategies. Advantages Decomposing one activity in smaller packages create new upstream activities with faster evolution and new downstream activities with lower sensitivity which create better opportunities for overlapping by reducing the risk of rework and delay. Disadvantages Decomposition involves re-analysis and double overlapping work of the new activities created. Key elements to ensure a high degree of success This strategy is only recommended when no other overlapping strategy is effective as it involves double overlapping work. Enhanced overlapping strategy framework Choosing the most appropriate strategy depends on the evolution and sensitivity characteristics of design activities but also the specific project conditions. Aligning strategies at the determinant level provides information about which of the strategies are most appropriate for a given context. Figure 3 is a basic framework that presents the appropriate strategies to be applied depending on the evolution and sensitivity characteristics of a pair of dependent activities (Bogus et al 2005). 48

Slow Evolution Fast Sensitivity Low High Overdesign Early release of preliminary info Prototyping No iteration/optimization Standardization Set-based design Overdesign No iteration/optimization Standardization Set-based design Decomposition Early freezing of design Overdesign Early release of preliminary info Prototyping Early freezing of design Overdesign Figure 3. Basic overlapping strategy framework (taken from Bogus et al. 2005, pp. 19) c. Advantages The major advantage brought by this technique is the potential reductions in design delivery. Overlapping sequential dependent design activities allows reducing the time normally required to complete project design, which therefore allows earlier design releases for construction execution. By adopting concurrent and overlapped design processes, construction can be expedited resulting in overall project schedule acceleration. d. Key elements to ensure a high degree of success Overlapping strategies always involve some level of risk. Therefore, its implementation has to follow a systematic analysis and thorough process to identify which overlapping strategies should be adopted and when these should be implemented to minimize the risks of delays and rework. The project or construction manager also needs to be aware and prepared to quickly respond if the overlapping strategy fails and take effective actions to mitigate any problems. e. Disadvantages In general, overlapping strategies for reducing project delivery time involve a certain amount of risk. The risk depends on the assumptions in which the decisions of beginning the downstream activity are based and the sensitivity of the downstream activity to changes on the assumptions made when all upstream information is finalized. As discussed before, activities with low sensitivity can be overlapped with lower risk of delay and rework than activities with high sensitivity. However activities with low sensitivity are not completely free of risk. It is not always possible to speed up the evolution characteristic of an activity as desired, and starting a low sensitive activity before all upstream information is complete also involves a certain degree of risk of delay and rework if the upstream information changes. 49

The most common dependencies among design activities are information and resources. The overlapping techniques presented focuses on information dependencies and the sensitivity of these dependencies to changes in upstream information. Thus the technique assumes that there are enough resources available to eliminate resource dependencies between activities, which is seldom the case in real life. Other risks and costs associated with overlapping include lack of design optimization and coordination, increased materials wastage, frequent change orders, inadequate coordination between design and construction, and inadequate scheduling of the work package interfaces. Other consequences include increased costs because of increased coordination loads in terms of the volume and frequency of communication between project team members. And, as concurrency increases on a project, the coordination requirements also increase along with its related coordination costs (Fazio et al. 1988, William 1995). f. Applicability and use There are a few steps that can be followed to enhance overlapping strategies applicability. The first step is to develop a critical path network schedule for the design process without considering any overlap between activities. The critical path schedule provides a basis against which time savings from overlapping strategies can be measured. Next, activities that belong to the critical path should be identified, along with the evolution and sensitivity characteristics of each one. This step can be accomplished by using the key determinants of evolution and sensitivity suggested earlier. Time savings are achieved only when activities on the critical path are overlapped. Once the evolution and sensitivity characteristics of dependent activities on the critical path have been identified, the third step is to determine the possible overlapping strategies for each pair using the framework provided in figure 3. Finally, the identified strategies are evaluated based on the potential consequences of their application. The decision of adopting a specific strategy for overlapping will depend on different factors including individual project circumstances, projects costs, design costs, and potential consequences of the selected strategy. Potential consequences of activity overlapping include increased costs due to lack of design optimization, increased materials wastage due to overdesign, increased costs and delays due to rework, among others. Therefore, the final decision on which activities to overlap and what strategy to employ will constitute a decision based on the trade-off between the potential time savings and the increased overall cost and potential rework. g. Other special characteristics One major consideration in the process of overlapping sequential activities is the decision of when, how and how much to overlap pairs of sequential activities. This can turn into a very complex process because of the amount of information that must be considered. Adopting analytical approaches can help to better process the information in order to make a good overlapping decision. The three major types of analytical procedures are optimization, simulation, and basic decision algorithms (Bogus et al. 2005). 50

Optimization approaches are mathematical models that use sequencing algorithms, such as the design structure matrix, and metaheuristics. Simulation approaches such as Monte Carlo simulation, Petri nets, and other dynamic simulation models also are used to answer the question of activity overlapping. The third approach is a basic decision algorithm which include of a series of heuristics. The process consists of a series of iterations until all activities in the critical path are reduced the maximum possible. This technique is the simplest one to implement, however it does not guarantee optimal solutions. Overlapping decision algorithm Bogus et al. propose a decision algorithm that addresses overlapping decisions and strategies and reduces project schedule while minimizing cost increases (Bogus et al. 2005). The process consists of the following steps: 1. Identify the activities that form the critical path in the non-overlapped schedule. 2. Identify the evolution and sensitivity characteristics of each activity on the critical path. 3. Evaluate the cost per day of overlapping for each strategy (or other appropriate time measure). 4. For each activity pair, select the strategy and overlap amount that results in the least cost increase. 5. Select the activity pair that has the lowest cost of overlapping and overlap that pair using the strategy elected in step 4 (in the case that two activity pairs result in the same cost, it is recommended to select the activity pair that is furthest upstream). 6. Re-run the schedule. 7. Repeat the process starting at the first step if more time savings is desired. Different views of this algorithm suggest different approaches to determine which pair of activities to overlap first. The most conservative school recommends selecting the activity pair that is earliest in the schedule, so that if the overlapping is not successful and results in rework, then there is more opportunities at the end of the project to make up for that extra time of rework. Other schools suggest overlapping first the activity pair that offers the most time savings. Lastly, activity pairs can be selected based on their possible risk of rework. One important consideration for the success of the algorithm is the input of data requirements. For example, the minimum cost approaches depends on the availability of data on the costconsequences of each overlapping strategy and overlap amount. The time-cost relationship of overlapping can be done by comparing projects that have employed overlapping strategies with projects that have not. This technique may not be the most applicable due to the lack of projects in which overlapping strategies have been proven and the lack of recorded information. Another approach to determine time-cost relationships is through the experience of project engineers and construction managers. Thus, the decision algorithm for determining the minimum cost overlapped schedule presents a simple process to solve the questions of when to overlap, how much to overlap, and how to overlap sequential activities. Nonetheless, the input information requirements can be difficult to obtain and involve additional work. 51

G. Lean design a. Technique Lean design is the application of lean production principles, to eliminate waste and non-value adding activities in the engineering and design process of project development. Lean design considers three perspectives to describe the design process: conversion, flow, and value generation (Freire and Alarcon 2002). Each of these conceptualizes the design process differently. The conversion view focuses on identifying the tasks and activities that are needed in a design job. However, conversion does not consider how to improve the use of resources (minimize unnecessary use), or how to guarantee that customer s requirements are met in the best way. Consequently, the conversion perspective leads the design industry to develop a work directed only to meet its business purpose. Under the flow perspective, the design process is seen as a flow of information that aims at reducing waste by minimizing the amount of time where information is not been used, such as the time spent inspecting information for conformance with requirements, the time spent reworking on information to realize conformance, and the time spent on moving information between the different members and disciplines involved in the development of the design. By conceptualizing design as a flow, integration of design with supply and construction is also improved (Ballard and Koskela 1998). Finally, modeling design from a value point of view focuses on customers requirements. In other words, the design process is directed towards lack of defects and product performance as valued by end-users. An effective design process involves the three views by generating activities that compose the total flow of design considering as well customer requirements in the process. Nonetheless, the conversion conceptualization has traditionally dominated over design scope, leaving aside the flow and value concepts of design. Lean design approaches design by integrating the three views (Freire and Alarcon 2002). b. Implementation Freire and Alarcon developed a methodology that applies lean design principles to the design and engineering process of a project with the objective of improving the internal design process and thereby facilitate project construction and start-up (Freire and Alarcon 2002). The technique consists of four parts: 1. Diagnosis and evaluation of design 2. Changes implementation 3. Control 4. Standardization Diagnosis and evaluation of design process The main purpose of this phase is to evaluate how the design process is performing in terms of the flow and value concepts by identifying waste and non-value adding activities. A number of 52

actions can be taken to determine the degrees of waste in the process and to find its major causes; these include performance indicators, process time distribution, value stream mapping and interviews. Common causes of activities that add no value to the design process or that result in waste are lack of knowledge of client requirements, interdisciplinary coordination, bureaucracy, and information unavailability (Freire and Alarcon 2002). Performance indicators Performance indicators can be used to obtain objective measures of design product quality in the process. The most common type of performance indicators are the total number of changes and the total number of errors and omissions in design drawings and/or documents. The total number of changes in design delivers the magnitude of changes in a project due to design changes. The second allows measuring the quality of the design. If design is released in packages, indicators can be applied to each package by measuring the number of changes and errors/omissions per package. Different packages that apply to different areas of construction may have different performance levels. Special attention should be given when measuring and comparing performance indicators in different environments. Time distribution in the process Not only it is important to know the time needed to develop a design, but also to determine how this time is distributed internally along the entire design process. In other words it is essential to identify the portion of time compared to the total design delivery duration that takes to complete each facet that makes up the design process. A design process is usually composed of data recollection, design, review, correction, release and distribution. During the entire process only some activities add value in design and the rest are usually waste that should be reduced or eliminated in order to speed up design delivery. Waste can be measured by obtaining the number of work days elapsed between the beginning and end of a drawing or document (Freire and Alarcon 2002). Value stream mapping Value stream mapping can be very useful for visualizing how the entire process works and to recognize the different activities and how they are involved in the process. Value stream mapping also permits identifying how time is distributed in each design stage (data recollection, design, review, corrections, release, and distribution). Interviews Because individuals are the ones involved in the process, their input can very helpful to identify possible areas of waste and its causes. Interviews can also be used to confirm and clarify the findings obtained with the other methods. Changes implementation This phase focuses on implementing changes based on the results obtained in the previous stage. Improvement actions in the design process can be applied in five different areas: client, administration, project, resources, and information. Examples of improvement actions include interactive coordination, intranet, checklists before design, checklists after design, value stream 53

mapping, and training. Improvement tools are considered and applied according to specific needs, and also based on the resources and individual conditions of the project. Interactive coordination refers to the simultaneous design and review of drawings by the different disciplines concerned to avoid interruptions and reduce the cycle time in each drawing. Typically, drawings spend more time waiting to be reviewed by each discipline before going back to the original designer. Parallel designing and reviewing drawings appreciably reduces time that adds no value to the design process. It also diminishes the amount of later corrections and interruptions. Effective means for achieving this can be the use of computer programs. One of the major causes of waste is information not available. Intranet is an effective means that allows a faster distribution of information which reduces the time spent searching for needed information not available. Data recollection for example is an area that presents great amounts of waiting times for information; intranet can reduce this and other waits. Checklists are an effective source for monitoring and control. Their main purpose is usually to review design. However, it can be of equal importance to use checklists before and during the design process as reminders and guides to keep in mind important considerations throughout design development. Checklists are tools that allow controlling final product characteristics and thereby reducing the number of errors. Value stream mapping allows recognizing alternative methods to improve information flow. The development of ideal value stream maps helps to visualize how the improved process should look like, which in consequence allows identifying the areas of waste and interruptions of flow. Training on lean principles permits resources to better understand the implementation process and the desired objectives so that their actions are properly directed towards project goals. Control After changes have been implemented, the next step is to evaluate performance aiming at achieving better control of results. Control can be achieved by measuring the new performance indicators and time distribution in the process where changes have been implemented and comparing the results with the performance indicators and time distributions obtained before the implementation of the changes. Standardization The objective of this phase is to introduce permanent improvements in the work methods by formalizing the changes that proved effective in eliminating waste and interruptions and in enhancing value-added activities in the design process. In other words, this phase standardizes the adoption of lean practices that consider flow and value in the design process. Standardization aims at maintaining the efficiency in what is left of the design development. c. Advantages As shown, the implementation of lean design practices drives to the reduction and elimination of activities and processes that add no value to the design process. Methodologies that follow lean principles also allow the identification of activities that generate value in design. By knowing 54

which activities add value to the process, more effort and work can be placed on them to exploit their significance and add value to the whole process. Identifying the internal time distribution of the design process helps to distinguish where time is being wasted and which activities have no added-value in the design development in order to reduce or eliminate them. However, identifying the process time distribution also shows which activities are the major factors that determine the total process duration. Strategies can be adopted to shorten the time required or to speed up the work on the identified critical design activities. A successful application of lean principles in the design process of a project improves the engineer process by reducing the number of design errors, cycle times and non-value adding activities. These improvements also result in increased productivity and reduced waste costs, ultimately translating into improvements in design delivery time and reduction of overall design costs. Finally, improved design processes deliver better quality products to construction. The improved design reduces the amount of changes and errors enabling construction to progress smoothly. Therefore, an improved design process improves construction processes too. d. Key elements to ensure a high degree of success Several elements are important in order to implement changes successfully (Freire and Alarcon 2002): o Teamwork: The design process is a work of multidisciplinary teams that may include the designer, client, construction manager, constructor, and even suppliers and vendors; therefore teamwork is very important in the success of design. o Flexibility: Because the application of lean design is not common to the design process, changes will be introduced that will require flexibility in the team. o Early implementation of changes: Implementing changes in the early phases of design offer more benefits because they are cheaper while changes in later phases usually involve extensive rework in engineering. o Constant control: Because the team is not used to focusing on the importance of flow of activities, they should be constantly controlled. o Awareness: An essential factor to achieve a successful implementation of lean design practices is to constantly create awareness in the people involved in the process because people tend to go back to work under old habits (the conversion model). In addition, the team has to understand the importance of the lean design application and the expected outcomes so team members can commit and act accordingly. o Feedback: Giving team members feedback about the lean design process and allowing them to be aware of the results also decrease resistance and enhance commitment to adopt the correct actions to take the process to success. e. Disadvantages The introduction of lean design principles in the design phase can be complicated and long. Diagnosing and identifying the level of waste in the process and the causes usually take extensive periods of time and effort. In addition, during this stage no actions are been taken yet towards delivery time reduction. 55

The second phase in which changes are being introduced and implemented can also turn into a challenging process as people may perceive that introducing the change and working under new practices can take more time than working under old and well-known methods. Furthermore, because the implementation of new procedures involves extra work, people may not recognize at the moment the potential pay-offs of the changes. Reluctance is even increased when changes are perceived as extra-work. Even after overcoming people s resistance, the implementation of changes in the process requires team members to work different from what they are used to. Adopting new practices and performing different from traditional entails a learning curve that requires certain time before people achieve an efficient stage of work. In order to validate the results of the control phase, performance measures and results have to be monitored for a suitable period of time before standardizing the processes. This step adds time that is not always available, particularly in the case of short projects. f. Applicability and use Lean design practices are effective in improving design delivery in terms of time, costs and quality. However, the process requires substantial work, effort and time. Consequently, the required investments on lean design implementation in projects of small size and short duration may become too high compared to the actual achievable benefits. Conversely, in large and complex projects the investments in lean techniques in the design stage can be vastly offset by the attainable improvements in the design and construction phases, and the potential reductions in overall project completion and costs. 56

H. Value engineering a. Technique Value engineering is defined as an analysis of the functions of a program, project, system, product, item of equipment, building, facility, service, or supply of an executive agency, performed by qualified agency or contractor personnel, directed at improving performance, reliability, quality, safety, and life cycle costs (DOD 2006). In construction, value engineering is a formal, logic and analytical process that searches for the best balance between project s required functions and its life cycle cost, while maintaining or improving project s value (CMAA 2006). Nonetheless, improved value can be represented in a series of different ways depending on the specific needs of the project. Thereby, as a schedule reduction technique, value engineering should focus in obtaining the maximum optimization of time. Value engineering is introduced in the design phase of construction projects to identify the best selection of design features, systems, equipment, and materials with the purpose of accomplishing schedule optimization at the lowest life cycle cost while maintaining the required performance, quality, reliability and safety. Value engineering in the early stages of design allows the consideration of alternative design ideas and solutions seeking at cost and time optimization over all phases of the project while enhancing its lifecycle performance. b. Implementation The implementation of value engineering relies on a multi-disciplined team and contractors know-how and ability to propose changes that cut costs and minimize schedule duration while enhancing or as a minimum maintaining quality, value, and functional performance (GSA 2006). Therefore, value engineering implementation is typically structured and applied in the design phase, and can be continued in the construction phase basing its foundations in the value engineering team and contractor s initiatives, commitment and support. Its effectiveness is enhanced even more when value engineering assessments continue throughout the life of the project including conceptualization and planning, design, construction, and operation and maintenance phases (CMAA 2006). Value engineering at early stages Value engineering analysis is usually introduced at the project conception phase or at the outsets of the engineering phase. The owner or construction manager brings the input of a multidisciplined team, or a value engineering/construction consultant. If the design and construction of the project are carried out by one same entity or a joint-venture, the actual contractor/constructor is brought into the value engineering team. Contractor s input in design and engineering enables the identification and evaluation of alternatives and changes in design that can add functional value in the construction and use of the completed facility while reducing construction, and operation and maintenance costs. The same type of evaluation during engineering and design development can be used to identify areas where construction means can be optimized and activity durations reduced. 57

Value engineering in the construction phase The application of value engineering in the construction phase is formally known as value engineering change proposal and it involves contractor s evaluation and proposal of changes that will enhance construction and overall project value (CMAA 2006). Thus, the contractor is encouraged to identify and suggest value engineering changes as its knowledge and expertise allow for generating valuable opportunities for savings in time and money. Through its experience and understanding of construction processes, contractors can realize potential value engineering alternatives related to construction requirements, materials, or methods that lead to optimizations in project delivery time and overall costs. Nonetheless, it is also important to make the contractor aware of the importance of not only preserving but enhancing facility performance, design quality, safety, and operability and maintenance. The changes proposed by the contractor should be evaluated by the construction manager or by the owner with the assessment of the construction manager to determine the possible benefits or effects in project time, performance and overall cost outlays. If the changes are approved, they should be then incorporated into the contract. The contractor receives an incentive payment, usually 50 percent of the construction cost savings (GSA 2006). c. Advantages The value engineering methodology creates an environment of collaboration and cooperation among the multi-disciplinary team and provides it with the tools to find creative and effective solutions to improve the project in terms of its schedule, costs and performance. The major benefit that can be obtained through an appropriate implementation of the value engineering program is the reduction in overall costs while the value and performance of the final product are enhanced (Palmer et al. 1996). Value engineering applied in the design phase promotes design effectiveness regarding project final cost, functionality and schedule. Thus, this technique allows the construction manager to take advantage of potential opportunities for delivering an improved project in shorter time. Value engineering approaches also enhance management decision-making capabilities as they present different alternatives for design, or different solutions to a problem when applied in phases other than engineering. Value engineering allows as well an improved management of change within the project team. The involvement of the value engineering team and particularly contractor s input in the design and engineering chapters of the project can also lead to superior constructability, enabling improvements in construction processes and performance. In addition, through their contribution, engineering errors and omissions can be minimized, reducing thereby changes and interruptions in construction. Constructability and operability input also enhance construction quality and safety. Finally, value engineering techniques provide better alignment between design, construction and customer needs. It also promotes creativity and inventiveness to think outside-the-box, which can result in potential improvements in all the areas that comprise the development of a project. 58

d. Key elements to ensure a high degree of success Value engineering should be implemented in the early stages of project design because design in its conceptual stages allows higher flexibility to introduce changes and, if needed, to modify the direction of design. Typically, the level of influence of decision decreases after conception of the engineering phase because decisions made in the early stages of the project allow higher commitment of resources (CII: Input Variables Impacting Design Effectiveness 1987). In addition, introducing construction consultant s knowledge and experience at the beginning stages facilitates early reviews of design with greater potential for identifying the opportunities for improving project lifecycle performance and duration. The likelihood of optimizing project costs also increases when changes are introduced in an early manner. The quality of the team is also a key to the success of the value engineering implementation. Members that form the value engineering team must have the required experience and qualifications to successfully execute the value engineering program. Management is crucial as well to support and lead the team. Good organization and management support in the design phase is fundamental again to allow an effective execution of engineering changes aiming at improving project performance, costs and delivery time while maintaining or enhancing design productivity. Design productivity refers to the cost, schedule, and efficiency of the design function itself (CII: Input Variables Impacting Design Effectiveness 1987). It is of vital importance that the construction manager monitors the effectiveness of the applied engineering changes by comparing the expected outcomes and savings to be achieved from value engineering implementation to the actual results. Constant control allows the construction manager to evaluate the impact and value of the changes introduced, and to take corrective actions and redirect value engineering team s efforts when the changes are not generating the anticipated outcomes. The performance of value engineering implementation, particularly value engineering change proposal at the construction phase, has better results when it is combined with effective contractor s incentives (CMAA 2006). e. Disadvantages The objectives and expected results from value engineering implementation can be wrongfully understood leading to an improper application of the technique. Value engineering has the potential to be incorrectly used as a technique to cut costs without considering project quality and functional performance over its entire lifecycle. Thus, engineering changes may be erroneously focused in solely reducing project costs at the price of sacrificing performance in other aspects of the project such as facility functionality, quality, operability, appearance and maintenance, among others. f. Applicability and use Presently, value engineering is a technique implemented in the development of projects in a frequent basis. This technique was first applied during construction in the form of value engineering change proposals to reduce overall construction costs. Nonetheless, the construction 59

industry now realizes that greater benefits can be obtained when value changes are introduced earlier in the conception and engineering stages of project development. Its application in the design phase is usually made on a consultancy basis. Its applicability is enhanced because many institutions offer private value engineering services, and the agency costs are easily offset by the savings attained in latter stages of the project. In the construction phase, value engineering is also a viable tool to identify potential opportunities for improvements. Its success relies directly on the contractor s ability and initiative to propose value engineering changes, which is also highly dependent of the contract provisions and incentive payments to the contractor. Value engineering programs are currently vastly used in the construction industry, and its use will continue to evolve as the industry realizes that its implementation rewards the entire construction community from owners, designers and engineers, contractors, subcontractors and suppliers, to end-users. 60

I. Four-dimensional visualization of construction scheduling a. Technique Technology is another tool that is available to today s construction managers. Research has shown that several new technologies have been developed that improve project performance in terms of schedule and acceleration. One such technology is the development of four-dimensional (4D) visualization of construction scheduling. This technology helps optimize construction operations, ultimately aiming at minimizing time and cost of the overall project. One of the first applications of 4D occurred at Virginia Tech in 1990. A system that combined scheduling networks with three-dimensional (3D) computer models was created to form a Visual Scheduling Simulation (VSS), aiming at enhancing traditional planning and scheduling techniques through the use of CAD technologies. The system generated a visual simulation of construction activities so that construction processes could be viewed over specific periods of time (Skolnick et al. 1990). This initiative introduced a new use of CAD technologies in the construction phase. Today, 3D and 4D animation tools are extendedly used with effective applications in the design and construction phases of projects. 4D planning models integrate 3D geometrical models with the fourth dimension of time by incorporating the associated project activity schedule. The result is a program that enables users, and particularly project and construction managers, the visualization of prospective scenarios where alternative construction sequences can be tested at any time. By visualizing different scenarios, logistics problems can be identified and therefore eliminated before they happen. In addition, 3D models linked to the schedule allow the analysis of resource requirements for each activity, material layout planning, and cost breakdown. 4D graphical visualization can also be used by construction managers for fast and efficient decision making or short term replanning. 4D technologies can be used as well by designers and engineers during design for checking constructability and improving construction performance through design. Thus, 4D visualization models represent an efficient tool to improve overall management and planning during design and construction. (Chau et al 2004). b. Implementation 4D models are composed of different tools that enable the interchange of data and allow the integration between the 3D geometrical model and the project schedule. Generally, this type of models employ AutoCad as the graphics tool and typical project scheduling programs such as Microsoft Project or Primavera as the scheduling tool. A data warehouse is also used to store the large amounts of data and information that the graphics tools and the scheduling program retrieve. The 3D design model is developed in AutoCad following regular design procedures. Design components are introduced in the program, and they are categorized according to the function they have in the actual construction. Typically, components can be divided in three categories: structural elements, operational objects, and temporary facilities. Structural elements can be further classified under subclasses of building elements such as floor, beam, column, slab, wall, and so on. The second component, operational objectives, allows the graphical representation of construction activities that are in progress for a particular structural component. These can be formwork erection, falsework installation, steel work and concrete work. Each of these is represented in the 3D model. Other features such as temporary facilities can also be included 61

because they occupy space even though they are not part of the permanent structure under construction (Chau et al. 2004). The schedule is developed in the adopted project scheduling program. Basic scheduling information is sufficient to develop the schedule and link it with the 3D model. Basic scheduling information includes activity durations, start dates and finish dates for each activity, and activity sequencing. The data warehouse stores the data generated by the 3D model and the schedule. It also enables a bi-directional flow of information between both features. Once the 3D model and the schedule have been completed, they are linked to generate the 4D representation. Through the 4D model, the user can specify different planning actions and view the output results from the system. For example, the user can play with the sequence of activities for a given construction planning stage, alter the duration of activities, add new scheduling data, and so on, and the system returns a visual representation of the product of the changes. Depending on the level of sophistication of the model, some may automatically add temporary facilities to the layout plan if needed. The results generated by the system follow a series of knowledge modules stored in a knowledge database that works under certain heuristic rules on construction technology. The 4D visualization model can also be altered directly. However, these modifications usually have to be again manually introduced in the schedule because most models do not automatically translate changes from the 4D model into the schedule. Research is still underway to improve this interface. c. Advantages 4D is a tool that has the potential to improve project performance through its application in the different stages of project development in different ways. During project design, 4D models can be used as a tool to improve design and construction performance. Construction visualization at this stage provides designers with a tool to analyze different alternatives for design and assess how each of these may affect construction. 4D representations can also be used to check and improve construction constructability. In the construction stages of the project, the construction manager can specify different planning actions and view the output results of the different tested alternatives through the 4D model. Thus, 4D provides construction managers with a tool to improve construction management decision-making as it facilitates the performance of what if scenarios on specific sections of construction. 4D representations also allow the development of improved construction sequences to reduce project durations. Problems associated with construction sequencing, temporary facility interferences and congestion can also be identified before they happen and properly addressed. As a result the schedule becomes a more accurate and achievable instrument, and the confidence among all teams and employees increases. Site management is also improved through the use of 4D visualization models in different ways. 4D generates different site facility layouts which permits the analysis of production flow and workspace utilization. 4D models visually integrate building elements, construction methods and trade space occupation requirements which provide the construction manager with the means to 62

improve sequencing and coordination of construction trades (Tan et al. 2005). 4D applications also allow the evaluation of site access such as access for the installation and use of large equipment and construction items. Further benefits to site management can be obtained by sharing the 4D representations of the project with subcontractors and particularly suppliers. Through the visualization of site layout, subcontractors and suppliers can plan better their work accounting for actual site access and availability of workspace. Through efficient communication and integration between the construction manager and subcontractors and suppliers along with the use of the 4D model, coordination problems can be eliminated resulting in fewer interruptions, enhancing thereby schedule performance. Assessment and better planning of situations that can be physically hazardous is another advantage of graphically visualizing the site. Other management tasks are also improved including operations and maintenance planning, and construction progress control and monitoring (Chau et al. 2004). The scheduling feature of the model along with the 4D technology enhance typical management functions such as the analysis of resource requirements for the activities under each different scenario including labor, material and equipment requirements. Estimation of quantities of construction materials can also be calculated as well as the estimation of costs. Thus, the model can assist the construction manager in the planning process by reducing waste costs. Under unexpected circumstances, site planning visualization enables the making of construction management decisions faster and more efficiently, resulting in better short-term planning or replanning. Additionally, visualization enhances communication and understanding among all parties involved. Consequently, planning visualization combined with construction scheduling tools enables improved planning and optimization of construction operations, which ultimately results in overall reduction of project delivery time and costs. d. Key elements to ensure a high degree of success The development of 3D and 4D applications require extensive knowledge and expertise. In order to develop the 3D model and link it to the time feature, technical knowledge in the use of AutoCAD or the selected graphic tool is indispensable. Designers and contractors normally have the essential levels of familiarity in the application of 3D technologies, however, further training may be required to effectively link and make use of the 4D design. In addition, high levels of knowledge in 3D and 4D are also expected at the management level. Management s involvement with the 4D representation is imperative to successfully take advantage of its features. Therefore, training has to be implemented at the management level as well. 3D and 4D technologies are tools that have no use if they are not properly communicated to all the parties involved in the project team. Constant and efficient communication is crucial to allow all parties under the different disciplines that comprise the construction process understand and take advantage of the 4D model. As mentioned before, 4D s use can be further exploited when project s 4D layouts are shared with subcontractors and suppliers, as it improves overall site coordination and management, leading ultimately to improved construction performance. 63

e. Disadvantages 4D is a technology tool that offers construction managers vast opportunities for construction and site management improvements; nevertheless, its application is associated with high implementation costs. In addition, the development of 4D models is a process that requires user s knowledge and expertise. The use of 4D technologies without the proper knowledge and tools can turn into a time-consuming and eventually unfeasible venture. f. Applicability and use In the past years, 4D techniques have been adopted in construction projects mostly as pilot models for experiencing its use and potential benefits. However, the construction community has begun to recognize the attainable improvements that 4D visualization allows in design and construction performance. The use of this technology within the industry is fairly increasing, particularly for improving the design and construction of large-sized and complex projects like the development of nuclear plants and such. Nonetheless, the high investments involved with its implementation have limited 4D s adoption in medium or small-sized projects. It appears that the benefits offered by 4D and similar technologies are maximized when implemented in large projects where the inversion in the 4D tool and the potential benefits can be offset by the usual incurred costs associated to projects of this complexity and size. In addition, the development of large and complex projects typically involves, by nature, other high technologies and resources with experience and knowledge in high technologies which enhances 4D s adoption success. 64

J. Overlapping sequential construction activities based on concurrent engineering a. Technique Reducing construction schedules is one effective way of reducing project delivery times. Another application of concurrent engineering to reduce project delivery time is the overlapping of dependent sequential activities during construction. By performing construction tasks concurrently, the construction schedule can be substantially accelerated, leading to earlier project completion. Activity dependencies determine the sequence of construction work in a project, and the critical path defines the completion time of a project. In a traditional approach downstream activities cannot be started until upstream activities are completed. Overlapping dependent sequential activities that are in the critical path, however, has the potential of reducing project delivery time by allowing activities to be performed concurrently (Bogus et al. 2005). Activity overlapping relies on decreasing or even removing the dependencies between activities to allow activities to proceed concurrently or out of sequence to reduce construction time. Construction activities dependencies are determined by different factors including information, resources (equipment, materials and labor), permissions, and physical constraints, but typically physical and resource constraints have the most influence in activity dependencies (Bogus et al. 2005). The technique presented herein considers only physical dependencies among activities by assuming that the design is complete, and that resources and permissions are provided as needed in order to eliminate resource and permissions constraints in dependencies among activities. The first step for implementing overlapping is to identify and classify activity dependencies as they are the main feature that determines schedule sequencing and thus construction delivery time. Dependencies among construction activities can be classified in four categories: physical relationships among building components, trade interaction, path interference, and code regulations (Echeverry et al. 1991). Physical relationships include building components that are spatially restricted, weather protected, or gravity supported by other components. Trade interaction refers to the different ways in which trades affect each other during the construction phase. Path interference relates to building components that must be moved around the jobsite in order to be installed. Finally, code regulations determine the sequencing of activities because these have to meet construction safety regulations. Physical relationships which include building components that are spatially restricted, weather protected, or gravity supported by other components can be further broken down into subcategories: building components that are supported by another component, covered by another component, embedded in another component such that combined may or may not generate a structural function, and weather protected by other component(s). Physical constraints can also take the form of the relative distance of two components to a third support and the flexibility of installation, or the relative distance to access a workspace (Echeverry et al. 1991). Similarly, trade interactions can also be divided in sub-categories such as space competition, resource limitations, unsafe environmental effects (when one crew may create an unsafe environment that limits other crew s work), requirement of service (if a crew requires a specific service to perform its work such as electricity), among others. 65

Physical constraints can also be classified as flexible and inflexible. Inflexible constraints include support by, covered by, embedded in that contributes to structural functions, requirement of service and code regulations, while the rest are considered flexible. Because physical constraints are a major determinant of activity dependencies, and activity dependencies dictate the schedule sequencing, it is important to identify and classify them before applying any overlapping technique. The extent to which two activities can be effectively overlapped depends upon the relationship between them. Commonly, these can be of four types: 1) dependent activities, 2) semiindependent activities, 3) independent activities, and 4) interdependent activities. When two activities are dependent, the downstream activity requires information from the upstream information before it can start. Semi-independent activities refer to the situation when only partial information from the upstream activity is required before the downstream activity can proceed. Independent activities do not require information from each other in order to begin. Interdependent activities involve a two-way information exchange between the activities before either can be completed (Prasad 1996). Overlapping independent activities do not involve any risk of delay or rework as they do not require information from each other to begin. Alternatively, dependent activities introduce risk when overlapped. Dependent activities rely upon information from upstream activities to proceed, and when two dependent activities are overlapped, the downstream activity starts before upstream information is complete. As a result, possible changes from upstream information may impact the downstream task resulting in possible delays and rework. In addition, the degree to which two dependent activities can be overlapped relies on the nature of information between them. This information exchange can be expressed in terms of the rate of evolution at which design information is generated by the upstream activity and the sensitivity of the downstream activity to changes in upstream information. Both characteristics are used to determine which strategies are the appropriate for achieving overlapping to accelerate construction and reduce overall project delivery time (Bogus et al. 2005). b. Implementation In construction, physical dependencies are practically related to workspace because any given construction task requires an available workspace. Hence, the extent to which dependent construction activities may be overlapped is directly related to the nature of the workspace exchange between the activities. Consequently, the rate of evolution of an upstream activity can be described in terms of the availability of upstream activities to release workspace and the sensitivity of downstream activities is described as the risk of delays and rework in downstream activities that start before upstream workspace is completed. Thus, when the upstream activity s workspace evolution is faster, overlapping becomes less risky (Bogus et al. 2005). By addressing workspace problems, it is possible to reduce or remove physical dependencies between activities so that overlapping can be successfully achieved without the risk of rework and delays, decreasing thereby construction s cycle time. Thus, strategies should be adopted to speed up the evolution of workspace use in upstream activities and to reduce the sensitivity of downstream activities to workspace availability. Bogus et al. suggest workspace subdivision as one strategy that speeds up evolution of workspace as it allows releasing sub-areas to perform 66

downstream tasks before the entire workspace becomes available (Bogus et al. 2005). Another recommended strategy is the construction of temporary work structures or supports. c. Advantages If correctly applied, overlapping sequential activities in the construction phase provide great opportunities for dramatically reducing the time required to complete the construction of any given facility, ultimately reducing overall project delivery time. In addition, by allowing construction activities to occur concurrently, overlapping strategies minimizes resources waiting times. When activities are executed in sequence, the downstream activity cannot start until the upstream task has been completed. This entails that, once the resources required to perform the downstream activity are free to do the downstream work, if the upstream activity has not been finalized yet these resources will have to remain idle until the downstream task can proceed. Typically, the project or construction managers will assign shortterm or minor activities to these resources until the actual activity for which they are intended is ready to begin. This and other similar actions have a significant impact in construction productivity. Overlapping, in the other hand, allows activities to happen concurrently, optimizing resources availability and in consequence improving construction productivity. In addition, construction costs related to resources usage can also decrease. d. Key elements to ensure a high degree of success Based on activities characteristics of evolution and sensitivity, overlapping can occur under different conditions (Krishnan et al. 1995). The first one is given when evolution of the upstream task is fast and the sensitivity of the downstream task is low. Dependent activities under these conditions represent the best opportunities for achieving overlapping with the least risk of delays or rework. When activity evolution and sensitivity are both slow, or when evolution is fast but sensitivity high, overlapping involves a fair degree of risks of delays and rework. Finally, when evolution of the upstream activity is low and sensitivity of the downstream task is high, overlapping should occur to the least degree possible (Krishnan et al. 1995). In any case, overlapping sequential dependent activities is a strategy that involves some degree of risk. Therefore, its implementation has to follow a systematic and thorough analysis to determine the best opportunities for overlapping with the minimum risk, and to be aware of the risks involved. It is also fundamental for the project or construction manager to be alert and prepared to effectively respond if the overlapping strategy fails and take rapid actions to mitigate possible consequences. e. Disadvantages Overlapping strategies have a high risk of rework and delays when the assumptions regarding upstream activities used to begin the downstream activities change. The risk of rework and delay increases when there is a higher degree of overlapping between activities. Activities with low sensitivity can be overlapped with lower risk of delay and rework than activities with high sensitivity. However overlapping activities with low downstream sensitivity do not offset completely the risk of rework. Sometimes, it is not possible to speed up the evolution characteristic of an activity as desired and starting a low sensitive activity before all 67

upstream information is complete can still result in delays and rework if the upstream information changes. As mentioned the major factors that create dependencies of construction activities include information, resources including equipment, materials and labor, permissions, and physical constraints, being physical constraints and resources as the most common ones. The overlapping technique presented to reduce construction delivery time of a project solely considers physical dependencies among activities and assumes a complete design and unlimited availability of resources and permissions, which is seldom the case in real construction environments. Overlapping strategies may compromise the quality of construction because of the use of upstream information when the upstream task in not complete. The percentage of defects can also increase, particularly when the strategy is adopted with sequential operations (Bogus et al. 2005). One key disadvantage associated with overlapping strategies applied to the construction phase is the potential increase in construction costs. Other risks and costs related to overlapping sequential construction activities include lack of coordination, increased materials wastage and inadequate scheduling of the work package interfaces. Other consequences include increased costs because of increased coordination loads in terms of the volume and frequency of communication between project team members. And as concurrency increases on a project, the coordination requirements also increase along with its related coordination costs (Fazio et al. 1988, William 1995). f. Applicability and use The first step for overlapping is to develop the critical path network schedule without considering any overlap between activities. The next step is to determine the critical path and the activities that belong to the critical path. Only overlapping activities that belong to the critical path will result in reduction of the overall construction schedule. Once the activities that belong to the critical path have been identified, the next step is to determine the evolution and sensitivity characteristics of each one. After this, the fourth step is to identify possible overlapping strategies for each pair of dependent activities. As mentioned before, one possible overlapping strategy is the subdivision of workspace to speed up the evolution of workspace to release sub-areas to downstream activities before the entire workspace is fully available. Finally, the identified strategies are evaluated based on potential consequences of their application. The decision of adopting a specific strategy for overlapping will depend on different factors including individual project circumstances, projects costs, construction costs, and potential consequences of the selected strategy such as risk of rework and delay. Therefore, the final decision on which activities to overlap and what strategy to employ will be made based on the trade-off between the potential savings in time and the increased cost or rework. g. Other special characteristics The decision of when, how and how much to overlap pairs of sequential activities when adopting overlapping strategies can turn into a very complex process because of the amount of information that has to be processed. The information that has to be considered in the overlapping decision comes from different levels within the organization or the project. Several analytical approaches have been suggested help to better process the information and therefore 68

improve the overlapping decision process. The three major analytical approaches involve optimization, simulation, and basic decision algorithms. Optimization approaches are used to help the overlapping decision making with the use of mathematical models comprised of sequencing algorithms, such as the design structure matrix, and metaheuristics. Simulation such as Monte Carlo simulation, Petri nets, and other dynamic simulation models are tools that model complex situations to help answer the question of activity overlapping. One last approach is a basic decision algorithm that includes of a series of heuristics. The process consists of a series of iterations until all activities in the critical path are reduced the maximum possible. This technique is the simplest one to implement, however it does not guarantee optimal solutions. Overlapping decision algorithm The decision algorithm is a basic solution to the overlapping question when the objective is to reduce the construction schedule while minimizing cost increases. The basis of the method is to standardize the decision process and consists of the following steps (Bogus et al. 2005): 1. Identify the activities that belong to the critical path in the non-overlapped schedule. 2. Identify the evolution and sensitivity characteristics of each activity on the critical path. 3. Evaluate the cost per day of overlapping for each strategy (or other appropriate time measure). 4. For each activity pair, select the strategy and overlap the amount that results in the least cost increase. 5. Select the activity pair that has the lowest cost of overlapping and overlap that pair using the strategy elected in step 4 (in the case that two activity pairs result in the same cost, it is recommended to select the activity pair that is furthest upstream). 6. Re-run the schedule. 7. Repeat the process starting at the first step if more time savings is desired. In addition to the minimum cost increase approach, there are other perspectives in the decision of which pair of activities to overlap first. One approach recommends to select the activity pair that is earliest in the schedule so that if the overlapping is not successful and results in rework, then there is more opportunities at the end of the project to make up for that extra time of rework. Other approaches suggest overlapping first the activity pair that presents the most time savings or the least risk of rework. The success of the decision algorithm also depends on the input of data requirements. Specifically, the minimum cost approach depends on the availability of data on the cost consequences of each overlapping strategy and overlap amount. The time-cost relationship of overlapping can be determined by comparing projects that have employed overlapping strategies with projects that have not. However this technique might not be the most applicable because of the lack of projects in which overlapping strategies have been applied and outcomes recorded. A more applicable way to define time-cost relationships is through the expert judgment of project engineers and construction managers based on knowledge and experience. Even though the decision algorithm for determining the minimum cost overlapped schedule seems as a simple approach to solve the questions of when to overlap, how much to overlap, and how to overlap sequential activities, the input information requirements can be difficult to 69

obtain. In addition, attaining accurate input information involves extra work in addition to the work involved in determining the selection strategy. 70

K. Fast-track a. Technique Fast-track is a technique that sets its basis in concurrency principles to achieve the simultaneous performance of product design and construction. It recurs to the overlapping of project design and construction, thus, early phases of the project are correspondingly under construction while later stages are still under design. This procedure of overlapping the design and construction can substantially reduce the total time required to reach project completion (Clough et al. 2000). b. Implementation Much of the information on this schedule acceleration technique is merely anecdotal because there is no formal process to fast-track a project. However, there is a series of general actions that can be taken to improve its implementation. Fast-tracking is generally defined as the compression of the design and construction schedule through overlapping activities or reduction in activities duration (Bogus et al. 2002). The typical fast-track process is to divide design activities into work packages. As design progresses and different phases are finalized, the work is released in packages for construction; hence construction is started before the entire design is complete. This process is also defined as phased construction. In some cases, fast-tracking involves starting construction on a work package before its design is completed. Fast-track implementation can begin by creating a viable phasing plan. This can be done with close input and coordination from members representing the design and construction phases, in addition to owner representatives and the construction manager. Input from design and construction members helps in identifying how the work should be divided into feasible packages for work. Once the design of each package is completed, it is immediately released for construction. Detailed construction schedules are developed as design packages are received. Nonetheless, an overall plan for construction can be developed following the phasing plan. Thus, dates and milestones determined in the phasing plan for design information release are used to develop construction planning in general terms. The process of fast-tracking, in addition, generates important flows of information that need to be effectively managed to allow design and construction progress satisfactorily. In order to speed project delivery time, design information needs to be released as quickly as possible for construction to proceed. This process involves increased flows of information, not only from upstream design to downstream construction, but design also requires feedback from construction outputs in order to improve the generated upstream information. Hence, construction performance with uncompleted design information generates outputs that have an important impact on design. It is crucial then to create an effective system for delivering output s feedback from construction to design in a promptly and accurate manner (Elvin 2003). c. Advantages Fast-tracking and phased construction can offer attractive advantages to the owner in terms of project time. Beginning project construction when design is still under execution can appreciably reduce project delivery time. 71

Additionally, overlapping project design and construction involves the need of integration and constant interaction between the design and construction teams. Thus, the input arriving from construction production through constant interaction allows engineers and designers to come up with innovative methods for speeding the design-construction process both related to the design itself and in the interdisciplinary relationship between project team members. The involvement of engineers and designers in the actual construction offers as well significant input in construction performance and design advance. Lastly, integration between the design and construction phases gives the opportunity for team collocation. Intellectual capital at the beginning stages of the project can derive into superior quality, improved constructability, and better means for construction, eventually leading to cost reduction, particularly project life-cycle costs. d. Key elements to ensure a high degree of success The following are key factors that enable the implementation of fast-track production to successfully reduce project delivery time: Communication The increased integration of different participants and schedules between design and construction generates higher levels of information. Effective communication is indispensable to effectively manage the increased information flows in the best interest of the project. When information is amplified and the means of communicating and transmitting information are not efficient, this can be translated into noise generation impossible to be understood and properly used by the end-users. Lack of effective and rapid means of communication between the different disciplines involved hinders fast-track s intention of speeding up project completion. Moreover, incorrect, overloaded or delayed information increase the schedule because extra time is spent in revisions, and improperly sacrificing revision time can have negative impacts in quality and increase the risks of rework. Strategies for overcoming these obstacles in an integrated project environment include developing a shared project language, enhancing iteration and feedback, and ensuring early input of downstream information-users, strategies that are discussed more in detail below (Elvin 2003). Building a shared language improves communication among the different parties. Face-to-face meetings allow developing a common language, but information technologies are also good tools to link all participants, and to allow faster and efficient information flow. Technology allows the capturing, storage, and retrieval of project knowledge and information, resulting into a valuable means of integration. Extranet is one such technology that supports an environment of constant communication and shared information. It allows the exchange of design information and documentation among team members at any time disregarding of their location. Extranets can also enable project members to optimize schedules by diminishing the time required for information exchange between the activities that add value to design and construction, reducing thus waste and elapsed time that add no value to the project. Iteration and feedback Iteration and feedback are very important aspects in fast-tracking projects. The overlapping of design and construction results in an iterative process in which not only the design process generates information input to construction, but construction also creates information that affects 72

design. Therefore, the project team has to develop a communication system with the capability of capturing feedback between activities as construction output becomes an important input that has to be properly delivered to improve design. Early downstream information user input As just mentioned, in projects undertaking fast-track approaches construction activities generate information that must be used by the designer, however, because of the traditional design process, designers do not always have the knowledge on how to extract and organize information that arrives from construction. In consequence, designers need to know how to play their new role of users of construction outputs information in order to pull out the proper information that allows improving design. Conversely, constructors need to be aware and inform designers of their own information needs so that proper design information is released to construction and within construction time requirements (Elvin 2003). Communication between designers and constructors enhances designer s knowledge regarding the construction process, which can lead into increased innovation. Thus, communication is very important to improve and speed up design, but also to create a design that improves and speeds up construction as well. The release of smaller packages of design information reduces the risk of rework and cost overruns, and they also allow a process where mutual feedback becomes less complex as the information to be exchanged is reduced. Small batches of information also allow a more flexible and rapid process, as a result, faster and better integration between design and construction can be achieved. Nonetheless, extremely small design batches can interfere with workflow and negatively affect productivity. Team Building Team building is indispensable in the adoption of fast-tracking. Engineers and contractors have to learn to work out their differences in a team approach, and create an environment in which objectives are team and project oriented. Direct experience supports the development of a shared understanding of the project s goals. Again, communication, common goal definition, effective rewards and shared responsibility can lead to effective teamwork. In addition to these, goal consensus, team autonomy, team-based rewards, and building trust among members multiply the potentials for fast-track success (Elvin 2003). Flexible project organization Flexibility is crucial to achieve integration. Individuals need to be flexible and open-minded to interact with the team and work in ways different from what they are habituated. Flexibility is also important to integrate design and construction activities. It should be provided not only in an individual level, but also in the project organization level. A fully integrated project environment supports collaboration among engineers, construction managers, and contractors. Flexibility also allows reducing overhead, smooth workflow and easing scheduling. Team collocation Team collocation is the share of intellectual capital at the beginning stages of the project to derive innovative and improved methods of construction and use of new materials. 73

Collocation can improve fast-track performance in different aspects. In a fast-track production, designers produce a series of information that are then passed to the constructors and transformed into work. If constructors are linked to designers through collocation before the information is produced, the data created in the information flow can be structured taking into consideration downstream needs. Additionally, collocation supports the creation of feedback loops between the design and construction phases. Collocation is also a great enabler of constructability. Planning Under traditional systems, construction is planned based on completed design specifications and documents. Fast-tracking forces overlap between the construction and design phases, where construction begins before design is complete; therefore not all the required information is available for construction planning. Thus, accurate and efficient planning becomes even more important as it has to consider concurrency in design and construction activities and still enable workflow during the construction phase. In fast-tracking projects, team work between designers and constructors is very important to generate the grounds for efficient and integrated planning. Flexible project definition Because fast-tracking increases the level of uncertainty in a project since construction is performed with uncompleted design information, it is important that the planning becomes project oriented and product oriented rather than detailed oriented, defining quality in terms of the finished product and the outcome and not based on the details of its configuration. This implies that specifications should give the construction team an agreed-to-measure for evaluating project performance, without committing to intricate design details too early in an environment of constant design changes (Elvin 2003). Synchronized workflow planning Under traditional project delivery approaches, the different phases of a project are fragmented leading to an outcome that is product of separate processes only linked together at one point. Under this perspective, workflow is mainly considered only during the construction phase. Fasttracking however requires the consideration of workflow throughout the integration of design and construction. Design and construction activities are reciprocally interdependent because information from one is an input in the other and the result of that input becomes an important input in the first. Therefore, planning has to consider workflow along the whole integrated process instead of pulling design and construction workflow apart. Efficient workflow planning between design and construction is better achieved through work packages. However, effective teamwork is also required to allow smooth integration and workflow between packages to maintain overall process workflow. e. Disadvantages As fast-tracking can offer significant opportunities for shortening project schedule, it can also be the source of coordination problems. Fast-tracking projects can be very sensitive to poor coordination and planning, which can consequently result into poor construction performance and increased rework, ultimately translating into project delays and increased overall costs. 74

Implementing fast-track to reduce project delivery time has the risk of affecting the quality of the final product. First, engineers are forced to release design information faster than traditionally, therefore they have to take less time in developing drawings and specifications which pushes designers to decrease revision time. Design deficiencies are more likely to pass overseeing when revisions are wrongly expedited. So, in addition to having to perform construction under the uncertainties involved with having incomplete information, deficiencies in design revision also increase the risk of construction rework and overall delays. Fast-tracking, by nature, forces designers to give less consideration to details, and because construction is performed based on information not complete, the lack of it is frequently replaced by assumptions. Lack of detail and erroneous assumptions can also compromise project quality, and introduce risks related to the safety functionality of the facility. Another potential disadvantage from fast-track projects is that compressed schedules do not always allow engineers to optimize every design. Because decisions are made under time pressures, there is not much time to consider and analyze different alternatives to find the most appropriate. Decisions have to be made with the information available at the time. Moreover, to speed up design delivery, facility performance is built to only meet a specific criterion, which hinders opportunities for optimization. This can equally create a negative impact on quality (Elvin 2003). The feedback processes that are caused by uncertainty make the construction process more dynamic and unstable, which can create a negative effect on project performance. When a project under fast-track is not properly planned, those feedback processes can cause disruptions affecting workflow which eventually will cause an adverse impact in productivity. Overhead expenses are increased under fast-track adoption too. The increased need for coordination and integration requires more people to be involved in the management and coordination of the project team. Additionally, site office facilities which are added to bring designers and constructors together successfully execute the fast-track project are typically associated to increased overhead expenses. f. Applicability and use Much of the applications of fast-track design and construction have been conducted within the design-build domain. Because under the design-build project delivery method both design and construction activities are included under a single contract, where design and construction are performed by the same organization, or a joint venture is agreed between a design and construction firms, the work can easily be divided into work packages and overlapped to reduce project duration (Barrie and Paulson 1992, Bogus et al. 2002). In addition, because the responsibility of both design and construction phases of the project fall under one party, there is more opportunity for design and construction integration. g. Other special characteristics One strategy for reducing project delivery time within fast-tracking is the overlap of design and construction activities. Bogus et al. (2002) have developed a methodology to reconfigure the design-construction interface for fast-track projects. The methodology aims at creating a process for overlapping design and construction activities with the objective of integrating designconstruction activities to reduce overall project delivery time. 75

The extent to which sequential activities can be overlapped is defined by the nature of the information exchange between those activities. This information exchange between activities can be described in terms of the natural rate of information development in the upstream task and the sensitivity of the downstream activity to changes in upstream information. The natural rate of information development in upstream activities is known as its evolution (Bogus et al. 2002). Within a project and generally speaking, upstream activities include project conception, specifications and design, while construction, operation, maintenance and decommissioning compose the downstream activities (de la Garza et al. 1994, Bogus et al. 2002). Only activities included on the critical path and activities with a high duration variance should be overlapped to achieve overall project schedule reduction. The degree to which two activities can be effectively overlapped depends on the relationship between them. Four types of relationships are possible between activities: 1) dependent activities, 2) semi-independent activities, 3) independent activities, and 4) interdependent activities. When two activities are dependent, the downstream activity requires information from the upstream activity before it can be started. Semi-independent activities are characterized by one activity requiring only partial information from the other activity to proceed. Independent activities require no information from other activities before they can be completed. Interdependent activities require a two-way information exchange between them before each can start (Bogus et al. 2002). Only independent activities can be overlapped with no risk of delay or rework. The other three types of relationships present a risk when overlapped. Overlapping semi-independent activities present the least risk, because the downstream activity requires only partial information from upstream tasks. Therefore, the downstream activity can start as soon as the required upstream information is released with little o no risk of delay or rework. In contrast, overlapping interdependent activities will always involve risk of delay or rework regardless of the degree of overlap, as both activities need a two-way information exchange. Dependent activities involve the highest risk of delay. When two activities are dependent, the downstream activity relies on information from the upstream activity to be completed. However, when two dependent activities are overlapped, the downstream activity has to start with uncompleted upstream information. Consequently, the potential risk of delay and rework is increased (Bogus et al. 2002). The present method for overlapping design and construction activities only considers independent and dependent activities. 76

Methodology for overlapping design and construction activities Figure 4 presents an overview of the methodology. Project decomposition Activity characterization Project database Activity relationships DSM algorithms Presumptive schedule Network scheduling program Enhanced DSM Overlapping opportunities Shared databases Ideal overlapped schedule Network scheduling program Project decomposition Figure 4. Proposed methodology (taken from Bogus et al. 2002, pp. 263) The first step is to decompose the project into design and construction activities or tasks. The purpose of dividing the project into activities is to form smaller packages of work that can be characterized and potentially overlapped. This decomposition can be quite general. The project is decomposed in design and construction activities. An alternative to decompose the work in smaller units is to identify similar work that can be done by one person or group. For example, a design activity can consist of the structural design of a certain component, and a construction activity can be the work on one element such as a wall, floor, foundation, etc. Design and construction activities can be divided into more detailed activities if desired. 77

Activity characterization The objective of this step is to identify the information generated by each design and construction task and the information required to begin subsequent design and construction tasks. In addition to identifying information requirements by the activities and the information produced, it is also important to identify when the information is produced and when it is required by each activity. This information is then used to characterize activities in terms of their evolution and sensitivity to upstream changes. Activity characterization allows the identification of appropriate overlapping strategies. Design activities can be characterized in terms of their internal iterations that evaluate multiple parameters or designs until eventually a final value or design is reached. Thus, evolution of design activities is defined in terms of the rate at which the initial range of possible design alternatives converge into the final design. In construction, an activity is a linear process in which the final output is already known before the project starts. Therefore, evolution of a construction activity can be defined in terms of the rate of production for that activity. Evolution of design activities ranges from fast to slow. An activity with fast evolution generates early a preliminary estimation of the final design. Conversely, a design activity with slow evolution has a large range of possible values for the final design and this range is not narrowed until the activity is almost completed. Design evolution can infinitely range among this two ends. For construction activities, Peña-Mora and Li define evolution as the task production rate defined by the progress curve for that task, which shows the percent complete of the work on the task versus time (Peña-Mora and Li 2001, Bogus et al. 2002). Thus, construction activities evolution can also range from fast to slow, and can be characterized in terms of its production rate. Sensitivity in both design and construction activities is given by taking the difference in percent progress on the activity divided by the perceived progress after a change is introduced in the activity due to a change in upstream information (Peña-Mora and Li 2001, Bogus et al. 2002). Both design and construction activities can have different ranges of sensitiveness. For instance, a downstream activity can be highly sensitive to changes in upstream information, so that the downstream activity cannot start until it receives the values from upstream task. Conversely, a downstream task can be very low sensitive to changes in upstream information so that most of the activity can be done without upstream values. The information needed to characterize activities in terms of their evolution and sensitivity can be collected from reviewing design and construction documentation for the project. Interviews with designers and constructors are also a suggested source to compile useful information. At this stage information technologies can become very handy to store the collected information in a project database and feed information as described in the following steps. Activity relationships After characterizing activities the next step is to define the type of relationships between activities. These can be independent, dependent and interdependent. The type of relationships will determine the overlapping strategies that are more appropriate to reduce project duration. 78

Accordingly, independent activities can be overlapped with no negative impact. Dependent activities can be overlapped with certain risk of delay and rework depending on the characteristics of the activities being overlapped and the amount of overlapping. However, in order to obtain project delivery time reduction, the overlapped activities have to be in the critical path. Bogus et al suggest a design structure matrix to identify activity relationships. The use of graphical methods is also recommended to represent the flow of information between activities (Bogus et al. 2002). The matrix will consist of the upstream and downstream activities listed in chronological order (upstream activities listed first) starting at the top and left-hand side of the matrix. Every time two activities are related, it should be marked in the matrix. The next step is to partition the matrix. The matrix is partitioned diagonally, and all the identified marks below the diagonal represent sequentially dependent activities as showed in figure 5. Partitioning is used to sort the activities in the matrix so to minimize the backward flow of information (Bogus et al. 2002). Because this methodology does not consider interdependent activities, these activities should be grouped to remove interdependencies. A Activity A B C D E B X C D X X E X X Figure 5. Partitioned design structure matrix (taken from Bogus et al. 2002, pp. 267) Presumptive schedule Using the partitioned design structure matrix, a presumptive schedule can be developed for design and construction activities. This schedule should be based on activity durations determined during the activity characterization, and start-to-finish relationships for dependent activities. Thus, under this schedule, all the required information is available for each activity to begin. Network scheduling tools can be used to develop the presumptive schedule. Enhanced design structure matrix The next step is to modify the presumptive schedule using an enhanced design structure matrix. The enhanced design structure matrix is obtained based on the found characterizations for each activity covered in previous steps. Potential characterizations of fast or slow for evolution, and high or low for sensitivity have to be incorporated to the portioned design structure matrix to generate the enhanced design structure matrix. The proposed way to incorporate these attributed 79

in the matrix is by replacing the marks previously recorded by a number from 1 to 4 as showed in figure 6. These numbers correspond to the following characteristics (Bogus et al. 2002): Number Characteristics 1 Fast evolution of upstream task and low sensitivity of downstream task to changes in upstream task 2 Fast evolution of upstream task and high sensitivity of downstream task to changes in upstream task 3 Slow evolution of upstream task and low sensitivity of downstream task to changes in upstream task 4 Slow evolution of upstream task and high sensitivity of downstream task to changes in upstream task Activity A B C D E A B 3 C D 4 2 E 2 4 Figure 6. Enhanced design structure matrix (taken from Bogus et al. 2002, pp. 268) Overlapping opportunities Based on the natural characteristics of evolution and sensitivity of activities, overlapping could be implemented after one of the following four strategies (Bogus et al. 2002). o If the upstream activity has slow evolution and the downstream activity has low sensitivity, overlapping through the exchange of preliminary design information is suggested. o If evolution in the upstream activity is fast, and sensitivity in the downstream activity is low, overlapping is recommended through exchange of preliminary design information and early finalization of the upstream design information. o If evolution in the upstream activity is slow and sensitivity in the downstream is high, then overlapping involves the highest risk and therefore it should be done by decomposing the activities into subactivities. 80

o If the upstream activity is characterized by fast evolution and the downstream activity by high sensitivity, the best situation for overlapping is by early finalization of upstream information. Bogus et al. suggest that the use of information technology tools allows altering the characteristics of evolution and sensitivity in activities (Bogus et al. 2002). For example, information technologies such as databases allow a rapid transmission of preliminary design information and of changes in design information to others affected in the process. Thus, the effective exchange of information through the use of information technologies presents opportunities for reducing the sensitivity in downstream construction activities. Equally, computerized tools allow designers to speed up the evolution of upstream design activities (Krishnan 1996, Bogus et al. 2002). In addition, activities characterization can also suggest the appropriate degree of overlap. Peña-Mora and Li suggest overlapping amounts that vary from 75 percent of overlap to no overlap at all (Bogus et al. 2002, Peña-Mora and Li 2001). Ideal overlap schedule The final stage in the implementation of the proposed methodology is to develop an ideal overlapped schedule based on the presumptive schedule developed in previous steps. The finishto-start relationships identified in the presumptive schedule are modified to start-to-start relationships with a specific overlap, which is determined based on the individual characterizations of evolution and sensitivity for those activities and the overlap rules discussed above. For instance, for a pair of activities with an evolution and sensitivity number 1, one possible strategy would be an overlap of 50 percent. For activities with evolution and sensitivity number 2 or 3, the overlap can be of 25 percent. Activities with number 4 evolution and sensitivity should not be overlapped. Finally, the appropriateness of overlapping strategies should also be determined considering their impact on cost, risks, and quality of the final product. 81

L. Just-in-time delivery a. Technique This technique is directly applied in the construction phase of a project. The intend of this concept is to deliver construction materials and equipment to the workplace just in time when they are needed without having to go to onsite storage before being used or installed. By minimizing storage on the field material and equipment, handling is also minimized, which consumes time and puts the material and equipment in more risk of damage (CII: The Project Manager s Playbook 2004). b. Implementation Executing just-in-time delivery requires extreme planning, coordinating, and expediting action because any failure in the delivery process can impact the planned schedule or change the planned schedule sequence, resulting in delays. In addition, delivery must be accurate and precise because interruptions in the process can disrupt flow reducing worker productivity. c. Advantages One important benefit of just-in-time delivery is the elimination of double handling of equipment and material on site, which therefore reduces the amount of work-hours. Minimizing double handling also minimizes the risks of material and equipment loss and damage. d. Key elements to ensure a high degree of success The most important element that compels the technique to success is the coordination and the precision of delivery. Commitment from fabricators and vendors to meet established dates and schedules is also a key to successfully carry on just-in-time deliveries. Frequent communication is also essential in the planning and coordination of the delivery of equipment and materials. Information technologies allow faster and improved communication among the different parties involved, enabling improved coordination. e. Disadvantages This technique is very vulnerable in the sense that any minimum failure or interruption in the delivery process can have strong impact in the schedule causing delays. Equally, when the delivery process does not reach continuity, interruptions may have an impact in workflow ultimately resulting in loss of productivity. f. Applicability and use Just-in-time delivery involves increased efforts in planning and coordination, otherwise the consequences of delivery failures can result into significant delays. Traditional tendencies in the construction industry prefer having equipment and materials stored onsite with anticipation to avoid the risks and consequences of delayed delivery. One way to make use of this technique 82

and take advantage of its benefits while reducing the risk of potential schedule impact if the in time delivery fails is to employ just-in-time delivery on equipment and material for activities that do not belong to the critical path. Equipment and material for critical path activities can be delivered on site prior than required following regular delivery approaches (CII: The Project Manager s Playbook 2004). 83

M. Lean construction Lean construction refers to the application of lean production principles to construction. Lean is a production management strategy for achieving significant, continuous improvements in the performance of the total business process of a contractor through the elimination of all wastes of time and other resources that do not add value to the product or service delivered to the customer (Shrier 2004). Thus, lean production focuses on the value of a product as perceived by the customer. Lean production recognizes two types of activities: conversion activities, which add value to the material or piece of information being transformed into a product, and product flows (inspection, waiting, etc.), through which the conversion activities are bound together, but which do not add value (Alarcon 1997). In construction, it can be said that value is determined by the client at the start of a project and described in terms of scope, cost and schedule. Alarcon explains that, in construction, management attention has focused mostly on improving the efficiency of the conversion processes; while flow of and between activities have not been much improved, resulting into uncertain and divergent flow processes, expansion of non value-adding activities and reduction of output value (Alarcon 1997). In consequence, the application of lean concepts to construction processes seeks at reducing the variability of workflow through the elimination of waste and activities that add no value to the construction processes, aiming ultimately at improving labor performance and productivity, thus improving overall project performance in terms of quality, schedule and costs (Thomas et al. 2003). Recent proponents of lean construction have proposed several methods to reduce variability in the construction process to improve the reliability of workflow and thereby improve productivity and project performance. The Last Planner methodology and the use of buffers are two applications of lean construction philosophies that can be implemented by the construction manager at the construction phase to achieve better productivity and improve construction performance, leading to overall improvements in project quality, and significant reductions in construction time and costs. 1. The Last Planner : Shielding production through weekly work plans a. Technique Ballard and Howell propose that performance to meet commitment plans during the construction phase can be improved by improving the quality of work assignments. Developing quality work assignments shields production units from work flow uncertainty, enabling those units to improve their own productivity, thus improving the productivity of the production units downstream. The associated reduction in task durations can lead to shorten overall project duration. Improvements in workflow through quality work assignments can also reduce the buffers previously needed to accommodate flow uncertainty, achieving further reductions in project time (Ballard and Howell 1998). Construction production control systems at the project level routinely consist of three stages: initial planning, look-ahead planning, and commitment planning. Initial planning involves the definition of the schedule in terms of the activities and the work that should be done prior the start of construction and the project budget. The look-ahead planning introduces resources in a 84

more detailed and adjusted schedule. Finally, commitment planning evaluates what should be done against what can be done based on actual availability of resources and completion of prerequisite work in order to commit to what can be done (Ballard and Howell 1998). Under current construction management practices, initial planning is the actual tool used to coordinate construction and drive work to completion of the project. Under initial planning, activities are identified, sequenced and scheduled to meet project objectives. In real practice, those doing the work are usually being committed by management to follow the initial schedule. The problem with this approach is that work is performed under a plan that only considers what should be done based on anticipated resource availability and not what can actually be done based on resource availability at that specific point in time. Actual resource availability can differ significantly from anticipated at initial planning. If that happens, crews are forced to deviate from the original schedule, and initial planning cannot produce the level of detail that is required to optimally perform and control production. To avoid these divergences, resource availability should be verified before starting work, because ability of getting the work done depends on the availability of resources. Traditional approaches to scheduling fail in considering this view. Inconsistencies between anticipated, actually needed, and actually available resources generate a series of uncertainties (ambiguities in design drawings, errors in take-off, fabrication errors requiring rework, delays in shipment, damage during handling, etc.) that affect the flow of resources before being used (Choo et al. 1999). Protecting field workers from those uncertainties through adequate planning can minimize the adverse impact they have on productivity. Thus, improved productivity allows construction to proceed faster resulting in shortened construction schedules and ultimately shortened project delivery time. b. Implementation Choo et al. propose a system for work planning named The Last Planner, which adopts a shielding method to overcome uncertainties encountered in construction processes (Choo et al. 1999). Their work is further supported by the implementation of a database application called WorkPlan that allows the creation of quality work plans. The Last Planner The Last Planner consists of the development of weekly work plans a reasonable time before the related work is performed. The key characteristic of these work plans is that they considering what part of the work that is planned to be done can actually be done, and then compel the project team to commit to do that work. Choo et al. suggest that choosing what work field workers will perform in the weekly plan from what they can perform should be made based on quality assignments, because weekly work plans are effective only when assignments meet specific quality requirements for definition, soundness, sequence, size and learning. Each of these is described below (Choo et al. 1999). o Definition: Are assignments specific enough that the right type and amount of materials can be collected, work can be coordinated with other trades, and at the end of the week it can be determined whether the assignment was completed? o Soundness: Are all assignments sound, i.e., are all materials on hand? Is design complete? Is prerequisite work complete? Note that make-ready work will remain for the foremen to do during the week, i.e., coordination with trades working in the same area, movement of 85

materials to the point of installation, etc. Nonetheless, the intent is to do whatever can be done to get the work ready before the week in which it is to be done. o Sequence: Are assignments selected from those that are sound in priority order and in constructability order? Are additional, lower-priority assignments identified as workable backlog, that is, are additional quality tasks available in the case assignments fail or productivity exceeds expectations? o Size: Are assignments sized to the productive capability of each crew or sub-crew, while still being achievable within the plan period? o Learning: Are assignments that are not completed within the week tracked and the reasons for deviation identified? Quality assignments shield production from workflow uncertainty. Failure of making quality assignments when planning for work leads production to nonproductive delays such as looking or waiting for resources, doing multiple stops and starts, proceeding under inefficient construction sequences, resulting in overall delays and rework. In addition, mismatch between labor capacity and workload leads to further adversely effects in productivity, decreasing performance and extending schedule durations (Ballard and Howell 1998). The Last Planner methodology helps generating assignments that meet quality criteria when developing the weekly work plans. WorkPlan is a constraint-based database that supports weekly work package scheduling taking into account the achievement of quality assignments of what can be done (Choo et al. 1999). Work Package Scheduling Work packages should be determined by a definite amount of similar work or a group of activities to be done in a well-defined area, using specific design information, material, labor, equipment, and with completed prerequisite work. Grouping similar work allows preserving flow of resources when crews move from one work area to the next, thus minimizing interruptions. It also enables a learning process in field workers as the same resources perform similar work, increasing thereby productivity (Choo et al.1999). To avoid multiple mobilizations and demobilizations, operations should not start unless they can be finished without interruptions. Operations that take more than a week should be divided in smaller units that can be completed in a week or less than a week, which allows statusing the work that has been completed at the end of the week, and subsequent work packages have to be appropriate sequenced to maintain continuity of the operation. The WorkPlan constraint-based database automates the development, and allows monitoring and controlling of work packages so that these are planned and performed under the Last Planner s concepts of production planning through quality assignments (Choo et al.1999). Work Package Features Every work package will have constraints that have to be satisfied in order to perform without interruptions. In general, construction work constraints can be categorized in five classes: constraints on contract, engineering, material, labor, equipment, and prerequisite work (Choo et al. 1999). 86

o Contract: Is this work package in the contract? Is it the result of a newly issued change order? Has the client approved this work? Has all coordination information been confirmed? Has the subcontract been issued? o Engineering: Have all submittals been turned in? Have all submittals been approved? Have all shop drawings been turned in? Have they all been approved? Are there any outstanding requests for information (RFIs)? Have all methods and procedures been decided? Have special permits that may be required been secured? Have assembly drawings been received? o Materials: Have all fabrication drawings been produced? Have all material requirements and sources for procurement been established? Have all requests for quotation (RFQs) been sent? Have all materials been purchased? Have all materials been fabricated? Have all the materials been delivered? Have all the materials been allocated? o Labor and equipment: Has the work package been scheduled? Are the required laborers available for the duration of the work? Is the required equipment available for the duration of the work? o Prerequisite work and site conditions: Has all prerequisite physical work been completed? Have all work areas been cleared so that the work package can begin? Is adequate storage space available to stage materials? Is the site readily accessible? Are weather forecasts compatible with work requirements? All work packages have to meet their constraints before they can be executed. If a work package does not meet any of the constraints specific for that work package, it should not be released for construction because its execution will likely be slowed down, delayed or interrupted (Choo et al. 1999). Implementation of WorkPlan WorkPlan s database management system was developed using Microsoft Access 7.0 and can be run using any version of Access. It allows the user to go step by step in the process of creating work packages, identifying constraints, ensuring constraint satisfaction, releasing work packages, and assigning resources. The program also allows collecting data related to the progress of work packages at the end of the week for monitoring and control (Choo et al. 1999). To begin, the user introduces into the database general information about the availability of resources at the project level and specific information of the work packages to be carried out. Because this information is traditionally found in the way of spreadsheets and word processor files, WorkPlan allows the capture and management of information in any of these electronic formats. A work package entry form allows the users to enter information related to the work package including work package s number, project number, description, duration, and budget cost. The user is also required to introduce input information about labor and equipment. For each work package input, the system generates five categories of constraints by default. These constraints relate to contract, engineering, materials, labor and equipment, and prerequisite work. The user can enter specific problems and solutions for each category. A preloaded list of problems is provided by the system, the user can also enter a new item if it is not in the preloaded list or if it needs to be recorded in more detail. If the problem is solved it can be unchecked and recorded for future reference. A resource assignment screen allows the user to schedule a released work package for execution and to assign resources to it. The user can introduce data related to the assigned recourses like 87

the number of hours that each resource will work on the specific work package. The system reports any scheduled overtime for the assigned resource and the additional charges. The user can also rework in the work package that reported resource overtime to try to balance it out. Once all constraints for a work package are satisfied and resources introduced, the work package can be released for construction. WorkPlan allows the user unreleasing a work package that has already been released if a constraint is not satisfied as expected. A remaining work feature provides the user with the estimation of the total cost of the work package based on the expected unit cost and the quantity of work that remains to be done. This estimated cost can be updated at anytime. By estimating the total cost of each work package, the construction manager can control and monitor project costs. The resource assignment screen can also be printed out for use in the field. Once the work associated with a work package has been completed, the actual number of hours completed by the crew on each specific assignment should be recorded. In the same way, work that was not completed as planned should also be recorded. This data is then introduced into the database to calculate work package completeness and costs. The system also requires the input of reasons why actual work did not meet the work planned which along with package percent completeness and actual costs can be used to measure reliability of the planning system. c. Advantages Advantages of weekly work planning based on quality work assignments Shielding production units from workflow uncertainty enables better productivity of the production unit that is shielded which thereby improves productivity of downstream processes. The result is reduction in task durations which leads to lower project costs and shorter overall durations. For instance, quality work assignments through weekly work plans allow minimization of redundant resources, avoidance of multiple stops and starts of operations which are best performed as a whole, efficient sequencing of activities, and so on, all of which have a considerable impact in project cost and duration (Choo et at.1999). Project duration can be further reduced from shortening the buffers previously needed to accommodate flow uncertainty. Improving the quality of assignments, in addition, add several advantages to the construction processes. Quality of construction is improved because resources including labor, material and equipment are available to have the work properly done. In addition, generating quality assignments increases the reliability of information which is indispensable for anticipating potential problems and enabling better planning. Work packages group similar work together which supports an environment of continuous flow of resources leading to fewer interruptions. This process speeds up workers learning curve enhancing better productivity. Traditional control systems forecast work to be completed based on the actual cost to date or the actual completed work to date. Then the forecasted work to be completed is calculated as an extrapolation of the average progress throughout the project or throughout the period of time being measured. Under this approach, future work plan tends to be based on how progress is 88

measured. On the other hand, weekly work plans based on quality assignments allows optimizing actual availability of resources to the maximum extent. Advantages of the use of WorkPlan WorkPlan management database can be run and used with any version of Microsoft Access, which facilitates its implementation as Microsoft Access is a program commonly found in the industry. Generating a weekly work plan on a computer saves time and also prevents errors. Additionally, automating the process through a database makes it possible to identify scheduling errors and defects, and these can be rectified before the work is performed. The program s different features facilitate quick planning to the user. WorkPlan makes the definition of constraints for each work package an easier and more accurate process. By having a pre-loaded list of constraints to check from, it is more certain that the work package will be released when it is ready to be worked on properly and without interruptions. WorkPlan s provides a real-time cost generation function that allows the evaluation of alternatives for resource allocations and a cross-allocation checking function that facilitates the detection of resource conflicts before they happen on the site. Both functions enable the improvement and optimization of resource management and planning. The resource assignment feature, in addition to providing the construction manager with a tool to correctly assign resources, also lets it play with the assignment of resources to fit into the work while minimizing the use of overtime. WorkPlan facilitates analysis and comparison between the work that was planned to be performed under a work package and the work that was actually completed. This attribute permit the construction manager to monitor and control project costs and, more importantly, to measure the reliability of the scheduling system. The reports on percent complete that the program provides can be used to see occurrences and detect key areas where to focus management attention in order to improve the reliability of the planning system. Finally, the system supports constant documenting, updating, and reporting of the status of the process of the work. This can be shared with all the parties involved, so that each person knows what others do and understand the implications of their own work in the performance of the work package and in the output of the entire construction process. d. Key elements to ensure a high degree of success Implementing weekly work plans is a practice that requires high levels of commitment, not only at the management level but also at the field level. The development of work plans for every week can be time consuming, which may hinder commitment from field workers. In addition, field workers may not be used to a formalized process for planning the work for the following week; therefore they might not appreciate its importance at the beginning of its implementation. Management support is very important in coordinating and guiding planning. Commitment and support from suppliers of information is also a key to the successful planning of quality work assignments. Achieving quality work assignments requires information from areas and parties not always directly related to the planning process. In order to satisfy assignments for definition, soundness, sequence, size and learning, it is important to gather 89

information related to different areas and to satisfy questions like is material availability enough for the work to be planned, is the design complete, are the prerequisite works completed, what are the crews available, and such (Choo et al. 1999). Furthermore, it is essential to scatter awareness of the importance of their input in people whose contribution may have a significant impact in work planning. The purposed methodology can be further improved by increasing the visibility of work flow. By involving supplier processes in the development of the work plans, work flow uncertainties can be reduced even more. This reduction of work flow uncertainty increases the reliability of work plans and the predictability of flow. In addition, with improved integrated production control systems, unavoidable delays and changes can be accommodated with minimum impact on the total project (Ballard and Howell 1998). e. Disadvantages One important disadvantage of lean construction practices is its reduced applicability. Most existing project management tools are usually based on critical path methods (CPM) which automate and facilitate project planning. However, most CPM based tools usually do not provide the appropriate support to field workers in production scheduling (Chua et al. 2003). Typical CPM models consider a limited number of constraints: activities sequencing based on precedence requirements and resource availability as anticipated when planning, failing in providing the means to effectively deal with the real availability of resources and information. As a result, CPM methods become useful only for project preplanning or planning before construction but not during actual construction. In consequence, scheduling tools available to construction and project managers make it difficult the implementation of accurate look-ahead planning, indispensable for reducing workflow uncertainties and for improving construction production. f. Applicability and use The attainable improvements in construction performance and production with the implementation of look-ahead planning through weekly work plans depends on the capabilities of the construction and project managers to plan for what can be done instead of what should be done. This is only achievable with scheduling tools that support the planning of quality assignments by allowing the identification of constraints including resource and information related, checking constraint satisfaction, allocating resources according to its availability, collecting field progress data, among others. As just mentioned, CPM methods usually provide the means for project pre-planning, but do not facilitate weekly work planning. As a result, this technique s applicability may be hindered by the lack of availability of the adequate scheduling tools and the lack of knowledge on how to properly make use of the available tools for improving look-ahead planning reliability. 2. Improving labor flow reliability for better productivity through the use of buffers a. Technique As previously mentioned, lean construction principles suggest that improving the reliability of flows in the construction process results in better labor and cost performance. In lean systems, 90

workflow refers to the movement of materials, information, and equipment through a system. Smooth workflow refers to the minimization of work interruptions and obstructions which can be achieved by having reliable material, information, and equipment available (Thomas et al. 2003). Variability leads to waste that hinders workflow and delays progress. Efficient management practices and better management of workflow is essential to eliminate waste, and enhance better productivity and performance, which can significantly impact project costs and schedule (Thomas et al. 2003). Horman and Thomas propose that one way to effectively manage the uncertainty and variability commonly found in construction processes is through the use of buffers. Buffers work to provide a cushion or shield against the negative impact of disruptions and variability. When buffers are properly used, they not only provide shield but they also have the ability to efficiently respond to conditions of variability enabling enhanced workflow and superior performance (Horman and Thomas 2005). b. Implementation There are different mechanisms that can operate as buffers, and different strategies can be implemented to manage buffers in order to achieve the appropriate levels of responsiveness. For example, additional money can be included in the budget to provide a buffer for budget contingencies. This type of buffer allows the project team to respond to unforeseen events minimizing possible negative impacts. Some buffers can be converted into a useful form faster than others. The readiness of this conversion defines the responsiveness of the buffer (Horman and Thomas 2005). For example, material and labor onsite can be effective mechanisms to rapidly respond to uncertainties and variability, while budget contingencies may take more time. Consequently, buffers have the ability of improving the efficiency of construction operations by absorbing the variability that construction conditions naturally generate. If properly applied, buffers not only provide responsiveness to variability issues but also can shield productivity from uncertainties in workflow maintaining thereby high performance There are many types of buffers at the work level. The most common ones are inventory, time lags and capacity buffers (Horman and Thomas 2005). Inventory buffers may include material stockpiles and work in progress. Time lags, also known as lead times, consist of time buffers. Capacity buffers refer to the use of additional equipment and craftsmen. Prior to the implementation of any kind of buffers, effective planning is indispensable to reduce variability as much as possible. However, because of the uncertainty and complexity of some construction projects, it is not always possible to eliminate all variability through only planning. Construction managers can recur to the adoption of buffers in combination with planning to better manage situations where uncertainty and variability have not radically been eliminated. Equally, if planning has effectively reduced variability and in so doing enabled workflow, the size of buffers can be reduced. Construction managers have to study the specific conditions of the project, the functions of the different types of buffers and the impact they may have according to the conditions of the project, to decide how to best locate and size buffers to achieve the seek improved performance. 91

Material stockpile buffers Materials buffers can be provided by producing more material between steps in an operation than what is right away needed in the next step. Material buffers in the form of stockpiles or inventory feed the next step and allow activities to proceed independently of any problem encountered in previous steps. These buffers allow construction processes to have continuity, improving workflow. The size of material stockpile buffers is very important and needs to be managed very carefully in order to achieve better production and increased labor performance. When buffers are oversized, they can become wasteful and impede effective performance and workflow. For example, if buffers are too large, productivity in operations can be hampered because workers may spend more time finding the right material or the area of work may become more congested and chaotic impeding efficient performance. However, if material stocks are too low, the consequences can be slowed and disrupted performance leading to reduced production. The relationship between the amount of material onsite and labor performance will depend on the conditions of the project, the work being performed and the productivity of the crews (Horman and Thomas 2005). Time lag buffers A time lag acts as a buffer when it is inserted between steps in an operation. Time lag buffers can be used to increase the starting certainty of an activity regarding of the conditions of previous activities. The use of time lags as buffers can also generate material stockpiles between steps, but the amounts generated tend to be minor and they are not likely to produce major impacts in workflow (Horman and Thomas 2005). Different conditions will have different time lag buffer requirements, and the decision of what is the appropriate time between tasks will depend on the construction manager s experience and judging based on the project conditions and needs. Capacity buffers A capacity buffer is produced when additional labor and equipment than the required are provided to complete an activity (Horman and Thomas 2005). Capacity buffers are not always recommended and their necessity can be avoided by effective management and planning. However, when these strategies fail and there is the likelihood that project complexity and uncertainties may affect project performance, capacity buffers provide the ability to quickly respond to unexpected circumstances. For that reason, additional capacity may be needed to provide the project with the capability of rapid responsiveness. Research has shown that if used correctly, capacity buffers can reduce project schedule by up to 35% and cost by up to 8% (Horman 2000, Horman and Thomas 2005). Nonetheless, the management of capacity buffers has to be done very carefully in order to produce advantages to the project instead of negative impacts. Buffers whose size is greater than required have the potential to convert into obstructions to productivity and project performance. For example, excessive labor in the form of schedule overtime and overmanning, if not properly applied, can alter labor productivity leading to poor project performance, increased delays, and increased costs. 92

Relationship between inventory and time lag buffers Research suggest that the decision of whether adopting inventory buffers and time lag buffers will depend on the priorities and needs of the project. Inventory buffers provide better continuity of work, while time lags increase the certainty of starting the next operation. In addition, the application of inventory buffers can sometimes produce time lags, just as time lag buffers may cause the generation of material stockpiles. Management strategies should focus on supplying the appropriate combination of inventory buffers and time lags to enhance continuity and certainty to improve workflow. The correct use of material buffers, time lags, and capacity buffers can result into smooth workflow and increased productivity, leading to significant reductions in project schedule and cost. In an analysis of the relationship between inventory (buffers) and construction labor performance conducted by Horman and Thomas, data collected from three commercial projects showed that the best labor performance occurred when inventory buffers were in a range of 4 to 5.5% and time lags ranged around 4 to 5 days (Horman and Thomas 2005). Results in the same study suggest that when time lags are too small, there seems to be a disruptive effect that adversely affects productivity. Howell et al s (1993) contend that when activities are tightly linked between each other, they are more susceptible to be affected by disruptions and variations. Results on the same analysis (Horman and Thomas 2005) confirm that when inventory buffers sizes are beyond specific levels, the effect can be disturbing in project performance. The appropriate size will vary from project to project, and from work to work. Management should evaluate project s particular circumstances in terms of, among others, the productivity of the crews and the work to be done, in order to implement the appropriate size of buffers to achieve satisfactory workflow. c. Advantages The most important characteristic of buffers is that they are a mechanism that provides rapid responsiveness to unforeseen and unexpected circumstances. Buffers ability to quickly respond to the variability of construction processes allows continuity and workflow while maintaining high productivity, enhancing therefore project performance. If used correctly, buffers can provide an environment that allows efficient operations by absorbing the fluctuations and variations in the traditional conditions of construction. For instance, buffers can absorb variations in production rates, problems with defective design, fabrication errors, poor workmanship, adverse weather, and such (Horman and Thomas 2005). Buffers can also be used in conjunction with efficient work planning, and hence enhance the reliability of workflow. Efficient planning plus the continuity of performance enabled with the use of buffers increases the chances for improved productivity which has the potential for significant impacts in project quality, cost and delivery time. d. Key elements to ensure a high degree of success The size of buffers is extremely important to assure successful results in productivity and labor performance. Buffers need to be of the appropriate size because if they are oversized they can generate congestions and disruptions impeding proper performance. On the other hand, continuity and production can be stopped, disrupted and slowed if buffer sizes are too low. Some research supports that schedule buffers should be placed at the end of unpredictable process, and 93

the buffer size should be determined based on the degree of uncertainties involved in the process (Ballard and Howell 1995, Park and Peña-Mora 2004). The implementation of buffers has a higher potential of successfully managing variability when used in combination with efficient work planning. Buffers by themselves have the capacity to provide quickly responsiveness to unexpected events. However, when planning is not effective, uncertainties and variability in the construction processes may increase the amount and size of buffer requirements, which can result into increased project costs and duration, and poor construction quality. Conversely, with improved planning of construction processes and workflow, variability can be partially or totally removed, reducing the size of buffer requirements. Efficient planning enhances the usefulness of buffers, leading to better project quality, and decreased project cost and time. e. Disadvantages One disadvantage generated by the use of buffers is found in their capacity to be reverted into a valuable form. Some buffers can be converted into a useful form more readily that others, and this readiness defines the responsiveness of the buffer. However, the more responsive the mechanism the more difficult it is to revert it to a valuable form if not completely consumed. For example, budget contingencies may not have a quick responsiveness under conditions of variability, but if the money is not spent it can easily be returned to the project team, the owner, or the applicable party. In the other hand, material stockpiles used as buffers provide fast responsiveness but when not used they can not easily revert into a useful form (Horman and Thomas 2005). Inappropriately sized buffers can worsen overall productivity in operations. When buffers are too low, performance can be slowed, interrupted and even stopped, but when they are oversized, buffers can be wasteful, and they can also impede workflow and hinder productivity. Capacity buffers not correctly used can also have counterproductive consequences into work performance. For example, when additional manpower and equipment is employed in the form of overtime and overmanning to accelerate the project, the excess manpower may be involved only during certain periods of time, and for different types of work, which can bring discontinuity and disruptions to other workers performance. There is no precise rule of what consists of an appropriate size and correct use of a buffer. Because of the variability of construction s nature, it is to the judge and experience of the construction manager to define the appropriate use of buffers and the size that better serves its purposes. Nevertheless, this is not an easy task because the use and size might also change from task to task. Therefore, if the construction manager does not have experience and knowledge to properly manage the use of buffers, the effects to project performance can be unfavorable, and moreover, it might be difficult to clearly recognize and define the adverse consequences and its causes. f. Applicability and use Buffering is a common practice in project planning and execution. Time lag buffers are traditionally used in project schedules as contingencies to guarantee activity and project completion on time. Inventory and capacity buffers are also frequently used to minimize work disruptions allowing construction processes to have continuity, and thus improving workflow. 94

However, the applicability and use of reliability buffers often present shortcomings related to how to plan and identify for the correct buffer placing and sizing. Buffer placing and sizing are typically decided and planned based on the experience and knowledge of the construction or project manager responsible for project planning and management. This strategy however is very dependable on the familiarity of the construction or project manager with the use of buffers and in their experience with managing same type of projects. To address this issue, different strategies to allow better planning for buffers and optimize their use are currently under research. One such strategy proposed by Park and Peña-Mora consists of the use of simulation technologies that integrate the simulation approach with the scheduling approach. This research supports that buffer reliability can be improved by pooling, resizing, relocating and recharacterizing contingency buffers through the dynamic project model. However further validation of this technique is needed (Park and Peña-Mora 2004). 95

N. Optimization of construction operations through simulation and genetic algorithms a. Technique Another tool available to construction managers to accelerate project completion is the use of simulation. Simulation optimization is defined as the process of maximizing information retrieval from simulation analysis without carrying out the analysis for all the combinations of input variables (Carson and Maria 1997, Marzouk and Moselhi 2004). Computer-based simulation is one technique that has been lately used to model uncertainties associated with construction operations, particularly earthmoving operations, with the objective of optimizing construction processes to reduce construction costs and delivery time. Discrete-event simulation has been used to analyze and design construction operations for over three decades (Martinez and Ioannou 1999). General-purpose simulation tools and languages have been developed with the intention of targeting a very broad domain and to be used with almost any type of operation. Conversely, special-purpose simulators are tools that have been designed for specific construction operations, targeting thus a narrower domain. In addition, frameworks such as modeling paradigm or simulation strategy and others have also been created to guide users in the development of simulation models (Hooper 1986, Balci 1988, Martinez and Ioannou 1999). The most important characteristics of simulation tools are their simulation strategies and their level of flexibility. Most simulation systems use two strategies: process interaction (PI) and activity scanning (AS). However, other models have also been implemented combining event scheduling (ES) with PI or AS. Flexibility refers to the capability of the simulation tool to model complex situations and to adapt to different application requirements. Thus, simulation systems can be very flexible and programmable, and allow for modeling complex and detailed construction operations; other systems can be very simple and non-programmable tools with limited modeling capabilities which therefore allow only for modeling simple construction operations. However, simple simulation systems still generate efficient results and are easier to learn. The difference between PI and AS strategies is given in the viewpoint from which they are written. PI models are written from the point of view of the entities or transactions that flow through the system. This strategy is intended for modeling operations where the moving entities have several attributes and the resources (including machines) that serve these entities have few attributes or interactions (Hooper 1986, Martinez and Ioannou 1999). AS strategies, on the other hand, are written from the point of view of the various activities being performed. AS models focus on identifying these activities and the conditions under which they take place. Whether a simulation tool is PI or AS-based has an important impact on the way the system is modeled and the way it is presented to the computer (Evans 1989, Martinez and Ioannou 1999). Some researchers argue that one strategy is superior to the other; nonetheless most available research agrees that both strategies have equal power and its usefulness depends rather in the system they are intended for. IP systems are more suitable for manufacturing purposes in which materials undergo a fixed pattern after they arrive to the system, and only leave as final products. In contrast, AS are more appropriate for modeling construction operations which involve many interacting resources that can perform in different states and where different conditions are required to carry out activities (Martinez and Ioannou 1999). Most models are also represented 96

using activity cycle diagrams (ACDs), which are networks that naturally describe three-phase AS models. Several general-purpose simulation systems have been developed specifically for modeling construction operations based on some form of ACDs and AS or three-phased AS strategies. Some of these include CYCLONE (Halpin and Rigs 1992), REQUE (Chang 1986), COOPS (Liu 1991), CIPROS (Odeh 1992), STEPS (McCahill and Bernold 1993), and STROBOSCOPE (Martinez 1996). Marzouk and Moselhi propose a framework called SimEarth that specifically allows the optimization of earthmoving operations through the use of computer simulation and genetic algorithms (Marzouk and Moselhi 2004). The optimization process uses computer simulation and genetic algorithms to search for a nearoptimum fleet configuration, taking into account their availability to contractors. The genetic algorithm considers a series of qualitative (i.e. type of resources and their combinations) and quantitative (i.e. quantity of each resource used) variables that determine the production of earthmoving operations. The simulation tool allows for estimating the time and cost of these operations which enable efficient planning of earthmoving operations (Marzouk and Moselhi 2004). By optimizing earthmoving operations, the time and cost of performing these can be minimized, reducing overall project schedule and costs. In addition, the framework allows for time-cost tradeoff analysis and the performance of what if scenarios with respect to fleet configurations. b. Implementation The SimEarth framework was developed and implemented in Microsoft environment, and consists of the following components: Earth Moving Simulation Program (EMSP), Equipment Cost Application (ECA), Equipment Database Application (EDA), Hauler s Travel Time Application (HTTA), Earth Moving Genetic Algorithm (EM_GA), and Output Reporting Module (ORM) (Marzouk and Moselhi 2004). ECA is a spreadsheet application developed to provide the user with the total hourly owning and operating costs and their respective breakdown. The application was design to be fully compatible with the Caterpillar performance handbook to enhance its applicability in the industry. EDA is a database that contains essential equipment characteristics such as hauler s allowable speeds, and it supplies the entire system with the information to be used in the simulation process. HTTA is a fuzzy clustering model that estimates hauler s travel time (Marzouk and Moselhi 2004). Earth Moving Simulation Program is the simulation tool that performs replications of earthmoving operations based on a predefined set of resources and entities. The program utilizes discrete event simulation and object-oriented modeling which facilitates the modeling of construction operations. EMSP contains the main activities of earthmoving operation which include loading, hauling, dumping, and returning. These are also classified into two types: bound-to-happen and conditional activities. The simulation program uses a three phase simulation approach by tracking activities in 3 phases. Thus, in phase one, the first activity is removed and the simulation time is advanced to 97

the next time. In phase two, all due bound-to-happen activities are carried out, and, in phase three, all possible conditional activities are performed. Earth Moving Simulation Program receives its input from the framework in two different ways, through parameters that are passed through its main function and by reading from external files. EMSP s main function passes different types of parameters including simulations performed either in a test manner or an analysis manner, interactions among equipment in the fleet under consideration, selected fleet scenario for simulation analysis, presence or use of second hauler, selected set of activities involved in the simulation process, number of simulation runs, and conditions for simulation analysis termination. The external files, on the other hand, feed the program with external information related to soil type, scope of work, equipment characteristics, and possible durations of the involved activities represented in the form of probability density functions (Marzouk and Moselhi 2004). To start the simulation analysis, the construction manager or the applicable user is required to specify the type of secondary activities involved in the project and the associated fleet scenario to be tested. Secondary activities can include spreading, compacting, and such. The main activities of loading, hauling, dumping and returning are selected by default. Then, the user has to specify the type of equipment available in the project to perform all main activities and the equipment available for each identified secondary activity and its corresponding model. After the equipment for both primary and secondary activities has being selected, the user introduces into the program all the relevant physical characteristics of the system such as characteristics of the material to be hauled, and any other that may impact any activity. Once all physical entities of the system have been established, these are mapped by their representative classes. For example, for the main activity of hauling, the class that represents this object contains the characteristics of the hauler unit including unit type, model, payload, and hourly owning and operating costs. These characteristics are the data member variables of that particular class. The framework s optimization module uses a genetic algorithm called Earth Moving Genetic Algorithm and Pareto optimality. The genetic algorithm contains two measures of fitness that allow the calculation of project duration and project total cost. These measures are obtained based on the pilot runs carried out by the simulation engine. Thus, based on the information contained in the database and inserted by the user, the simulation program runs a series of replications of the earth operation processes under different pre-established scenarios, and the generic algorithm calculates the time required by each piece of equipment to complete its task. The total cost is also calculated based on direct and indirect costs. The direct costs are estimated based on the time equipment is assigned to the project, and its associated owning and operating costs. The indirect costs, on the other hand, can be of two types, time related and time independent. The user is thereby able to define the types of indirect costs that are to be applied according to project characteristics. The following example illustrates the use of the program in selecting the most appropriate fleet configuration to optimize earthmoving operations. Three different fleet scenarios are considered as shown in table 3 to find the near-optimum fleet configuration through simulation techniques. The example involves moving a specific amount of earth from a certain distance. It is necessary to know specific characteristics of the soil such as loose and bank densities. All these parameters, along with the characteristics of each fleet scenario are introduced into the simulation system. The user is also required to introduce the probability distributions associated with the duration of the main and secondary activities which in the example are spreading and compacting. 98

Equipment characteristics Scenario 1 Scenario 2 Scenario 3 Loaders Range (1-10) for scenarios Type CAT 992G CAT 990SII CAT 988F Bucket capacity (m3) 12.3 9.2 6.9 No. of passes 4 3 3 Hourly owning and operating cost (dollars/h) 300 250 175 Haulers Range (15-20) for scenarios Type CAT 777D CAT 773D CAT 769C Payload (ton) 81.7 45.8 33.46 Hourly owning and operating cost (dollars/h) 215 160 130 Dozers Range (1-10) for scenarios Type CAT D8R Cycle production (m3) 27 Hourly owning and operating cost (dollars/h) 150 Soil Compactors Range (1-10) for scenarios Type CAT CS-583C Cycle production (m3) 19.1 Hourly owning and operating cost (dollars/h) 90 Table 3. Characteristics of fleet scenarios (taken from Marzouk and Moselhi 2004, pp. 111) Based on the inputs made by the user, the simulation engine carries out a series of pilot runs, and the generic algorithm calculates the required measures of fitness of project total duration and project total cost. The system then returns the calculated total project duration based on entered information related to the total quantity of earth to be moved, the daily production, and the scheduled hours per day; and it calculates project total cost from the scheduled hours per day, the equipment hourly cost, the number of equipment associated to each scenario, the total quantity of earth to be moved, daily production, scheduled working days per month, time-related indirect cost, and time-independent indirect cost (Marzouk and Moselhi 2004). Ultimately, the system provides the construction manager or the applicable user with two solutions. The first one contains the minimum calculated cost and its associated duration, and the second solution provides the minimum calculated duration and its associated cost. Thus, the construction manager can perform time-cost tradeoff analysis and select the fleet configuration that best minimizes operations duration. c. Advantages Computer simulation and genetic algorithms have been extendedly applied within the construction industry because they are an efficient tool to optimize construction operations. By optimizing construction operations, the time and cost of carrying them out is minimized. Optimization of construction operations also enhances the efficiency of construction processes. The framework presented allows the identification of a near-optimum fleet for earthmoving operations while it presents a series of useful features. It develops efficient optimizations as it takes into account both qualitative variables such as the type of resources and combinations 99

used, etc., and quantitative variables such as the quantity of each resource used, etc. In addition the model considers and accounts for actual availability of equipment. Finally, it allows users to consider and evaluate what if scenarios related to fleet configurations and time-cost tradeoff analysis. All these features allow the construction manager to efficiently reduce the uncertainty associated with construction operations and therefore improve construction planning. d. Key elements to ensure a high degree of success The implementation of technologies involving simulation and the use of genetic algorithms require knowledge and expertise. Therefore, training is substantial for a proper implementation of these techniques. During experimentations with simulation technologies, the construction manager or engineer changes the different parameters in the model or the logic of the operations. Therefore, it is also important that the construction manager or the engineer learns how to properly enter the needed inputs and how to control the different permitted options that the program allows in order to obtain adequate results. Despite of its powerful features, the simulation system is only a tool that allows the engineer to find optimality searches related to construction operations, or the near-optimum fleet in the case of the framework presented. The search for this optimality is modeled by the simulation program but it has to be guided by the knowledge and experience of the engineering and construction manager. Therefore, knowledge and understanding of the operations under analysis is also vital for the users to be able to efficiently employ simulation and optimize construction operations. The development of complex simulation models can also be substantially enhanced when combined with 3D models. Simulation modeling and 3D visualizations can be very helpful in designing complex construction operations and making optimal decisions. A visualized simulated representation of the construction operation is a more realistic tool which provides the user with comprehendible feedback, indispensable for adequate analysis. In addition, the 3D visualization tool can provide valuable insight into the details of construction operations that are usually hard to perceive and therefore disregarded (Kamat and Martinez 2001). e. Disadvantages Typically, the effort and knowledge involved in the development and implementation of simulation models tend to limit the use of simulation in construction (Mohamed and AbouRizk, 2005). Building and utilizing simulation applications require experience, technical knowledge of the construction system and of the simulation technology, and substantial investments in time and money, and given the relatively short duration of a project s construction process, the potential achievable benefits may not always be perceived as to be worth the associated costs of implementation. Furthermore, without the proper expertise and tools, modeling the simulation system can become a time consuming and ultimately worthless investment (Mohamed and AbouRizk, 2005). Once the model has being built, its utilization is not a trivial process. Carrying out simulation runs and experimentations typically involve modifications in the topology of the model which again requires more effort, knowledge and expertise (Mohamed and AbouRizk, 2005). 100

f. Applicability and use There is an increasing number of simulation and genetic algorithm applications within the construction industry that have been developed aiming at optimizing operations during construction with the intention of minimizing the total duration and costs of these. Because of the potential benefits and advantages that simulation tools offer in the analysis and planning of construction, its adoption has been slowly gaining acceptance within the industry. However, there are also a series of important factors that have hindered a broader implementation of simulation technologies. First, as most technologies, implementing simulation models require high investments substantially increasing construction costs. Then, effort, time, knowledge and experience are also prerequisites not only to build the simulation model but to run it as well. Finally, because of the uniqueness of construction projects, the development of the simulation representation is a time-consuming task compared to overall construction duration. All of these issues have contributed to a limited applicability of simulation and such technologies (Mohamed and AbouRizk, 2005). 101

O. Time-cost trade-offs a. Technique The process of accelerating the duration of a project based on time-cost trade-offs is usually known as crashing. Crashing refers to the reduction of activity durations in the construction phase of a project with the objective of reducing construction schedule duration (Callahan et al. 1992). Crashing is a systematic and analytical process that examines all the activities in the schedule and focuses particularly in those activities on the critical path in order to achieve overall reduction. The crashing process uses an assessment of activity variable cost with time which allows identifying which activity durations should be reduced to economically minimize the cost of accelerating construction duration (Callahan et al. 1992). There are several ways to reduce activity durations, and many combinations of activity durations and costs that have to be considered and analyzed to achieve duration reduction for the minimum cost. Crashing therefore enables the construction manager to reduce overall project completion by accelerating construction delivery time while minimizing the added costs of acceleration. b. Implementation Activities on a project can be crashed in one of the following ways (Callahan et al. 1992): o Extended workdays or overtime o Multiple-shift work o Increasing the number of craftsmen or overmanning o Using larger or more productive equipment o Using materials with faster installation methods o Using alternate construction methods or sequences Extended workdays or scheduled overtime refers to the planned decision by the project or construction manager to accelerate the progress of the work by scheduling more than 8 hours per day or 40 hours per week for an extended period of time for much of the crafts workforce (Thomas and Raynar 1997). The intention of extending workdays through scheduled overtime is to reduce the total time required to complete an activity. Overtime can occur in different schedules: 5 days of 10 hours per day, 7 days of 8 hours per day, 6 days of 10 hours per day, or 7 days of 10 hours per day, which can decrease activity durations by up to 33 percent (Callahan et al. 1992). Project duration can also be reduced by accelerating construction progress through the use of additional work shifts. Shift work is defined as the hours worked by a second group of craftsmen whose work on a project is performed after the first or primary work force of the same trade has retired for the day (Hanna et al. 2005). The use of multiple shifts is an effective tool to achieve the completion of activities in fewer days as it approximately doubles the amount of work hours per week. Consequently, working one or two additional shifts can lead to large reductions in activity durations, ultimately resulting in acceleration of overall construction and project delivery time. Increasing the number of craftsmen is another technique to accelerate construction schedule in order to achieve faster project completion. Increasing the amount of workers is usually known as overmanning. Overmanning can be understood in two different ways. First, it can be referred to the increase in crew sizes in an amount that exceeds the optimal crew size. The optimal crew 102

size is the minimum amount of workers required to complete a task in the assigned period of time. Overmanning can also be defined as an increase of the peak number of workers of the same trade over actual average manpower during project (Hanna et al. 2005). Both approaches of increasing the amount of craftspeople allow progressing at a faster rate to diminish the time it takes to complete activities. Finally, the use of larger or faster equipment, the use of materials with faster installation methods and the use of alternate construction methods or activity sequences can also enable reductions in project duration. The adoption of any of these techniques will lead to substantial reductions in construction duration, but with an increase in project costs. It is therefore important to determine how much the duration of each individual activity can be reduced and at what cost. Determining how much an activity can be reduced and the costs involved requires scheduling and estimating experience and knowledge. Once the construction manager has evaluated and determined the best approach to reduce activity durations, a time-cost analysis can be used to establish the alternative durations and costs that should be crashed for minimizing the cost of accelerating total project completion. Time-cost analysis Following the traditional steps to develop a schedule of construction activities, the first step in the crashing process is to determine the relationship between duration and cost for each activity based on basic planning and estimating information. There can be several possible combinations of duration and cost for any given activity. Based on these possible combinations, the construction manager develops a duration-cost relationship for each activity. The construction manager then evaluates the options available and defines the durations for each activity to be used in the construction schedule. The schedule produced with these activity durations will be used as the baseline schedule for crashing. Once the schedule baseline has been generated, the construction manager can start the time-cost analysis using the duration-cost relationship previously identified. The relationship can be represented in a graphic form as shown in figure 7. Point I represents the point of minimum activity duration and maximum activity cost; this point is a limiting point for the duration. Point II represents the minimum activity cost and the associated activity duration corresponding to that cost. Point I is often referred to as the crash cost and point II represents the normal duration. Similarly, point I also establishes the crash duration and point II the normal cost (Callahan et al. 1992). 103

Activity Cost ($) CC I CC = Crash cost NC = Normal cost CD = Crash duration ND = Normal duration NC II CD Activity duration (days) ND Figure 7. Duration cost relationship (taken from Callahan et al. 1992, pp. 261) Although figure 7 is represented by a straight line, the relationship between the duration and cost of an activity is seldom linear. However, an approximation can be obtained by assuming a linear relationship between durations and costs resulting into a straight line. In the cases in which the relationship is not close to linear, the different duration-cost points can be connected by drawing a line between the points in the graph resulting in various linear segments as shown in figure 8. The slope of the graphic or the slope of the segments is used to determine what activities and durations will be selected for use in crashing the overall schedule. As it will be shown later, the same slope is used to determine the impact that the reduction of schedule duration has on project costs. The slope of the line can be mathematically calculated by using the coordinates on the duration-cost graph. 34,750 34,500 Activity cost ($) 34,250 S1 34,000 33,750 33,500 S2 33,250 35 40 45 50 55 Activity duration (days) Figure 8. Duration cost relationship of a particular activity (taken from Callahan et al. 1992, pp. 263) 104

Since a close approximation has been made by a straight line between the crash cost and the normal duration points of any given activity, the cost-per-day can be calculated by calculating the slope using the following formula (Callahan et al. 1992): S = (CC NC) / (ND CD) where, CC = crash cost NC = normal cost ND = normal duration CD = crash duration S = slope Figure 8 illustrates the duration-cost relationship of a particular activity. The crash-cost slopes for this activity are: S1 = ($33,936 - $33,250) / (51-42) = $76.22 / day S2 = ($34,632 - $33,946) / (42 37) = $139.20 / day Following this process, the cost-per-day for each activity considered for crashing can be obtained. An example is used next to illustrate the process of crashing a project schedule. Figure 9 shows the construction network for a given project. Table 4 shows the duration-cost relationships for the activities identified in the construction network. A 120 B C D E 20 40 30 50 F 60 Figure 9. Example project network (taken from Callahan et al. 1992, pp. 264) Normal Crash Normal Crash Activity Duration (days) Duration (days) cost cost A 120 110 $12,000 $14,000 B* 20 15 $1,800 $2,800 C* 40 30 $16,000 $22,000 D* 30 20 $1,400 $2,000 E* 50 40 $3,600 $4,800 F 60 45 $13,500 $18,000 * Critical path activity Table 4. Duration-cost relationship for the activities in the example project network (taken from Callahan et al. 1992, pp. 264) 105

Assuming that the duration-cost relationship for each activity is linear, the crash-cost slope for each activity is determined using the crash cost (CC), normal cost (NC), normal duration (ND) and crash duration (CD) of each activity as follows: S = (CC NC) / (ND CD) SA = ($14,000 - $12,000) / (120 100) = $100/day SB = ($2,800 $1,800) / (20 15) = $200/day SC = ($22,000 - $16,000) / (40 30) = $600/day SD = ($2,000 - $1,400) / (30 20) = $60/day SE = ($4,800 - $3,600) / (50 40) = $120/day SF = ($18,000 - $13,500) / (60 45) = $300/day The normal cost for the project is the sum of the normal cost for each activity, and the normal duration is the duration of the activities in the critical path for the given normal costs. The normal cost for the example project is $48,300 and the normal duration is 140 days. The duration of each activity has to be crashed one by one in order to crash the total duration of the schedule. The first activities to be crashed are the ones that fall into the critical path and add the least cost to the overall project cost. The cost that any crashed activity would add is given by the least cost slope, and its duration can be reduced only to its crashed duration and as long as the critical path does not change or a new critical path is created. In the example, the first activity that should be crashed is activity D because it is in the critical path and its cost is only $60 per day. Crashing activity D by its crash duration of 20 days leads to an overall schedule reduction of 10 days from its previous completion time of 140 days, resulting into a new completion length of 130 days. The revised network is shown in figure 10. The cost of crashing activity D is found by multiplying its cost per day by the number of days crashed. Activity D increases the total cost of the project by $600 ($60 per day times 10 days), from $48,300 to $48,900. A 120 B C D E 20 40 20 50 F 60 Figure 10. Network after one step of compression (taken from Callahan et al. 1992, pp. 265) The next activity to crash would be activity E because it belongs to the critical path and has the least cost per day. If the critical path changes, the next activity to crash is the one with the leastcost slope that falls into the new critical path. In the example, activity E is the next activity in the critical path that adds the least cost to the project. This activity can be reduced from 50 to 40 days, reducing the project schedule by 10 days. By reducing project duration by 10 days, activity E increases the cost of the project by $120 per day or $1200. Therefore, the new total project 106

duration is 120 days with a cost of $50,100. After crashing activity E, the revised project network has now 3 critical paths (A, B-C-D-E, and B-F-E) as illustrated in figure 11. A 120 B C D E 20 40 20 40 F 60 Figure 11. Network after two steps of compression (taken from Callahan et al. 1992, pp. 267) Since the network has now multiple critical paths, it is necessary to crash one activity on each critical path to achieve overall schedule reduction. The activity from each path that gives the most reduction for the least cost is selected for crashing. The combination of cost slopes of each activity is used to calculate the total cost increase per day. Activity A ($100/day) and activity B ($200/day) are the next activities crashed and combined add $300 per day to the project cost. This combination crashes the project schedule from 120 days to 115 days for the least cost, resulting in a new total project cost of $51,600. The last activities to crash are activity A ($100/day), activity C ($600/day), and activity F ($300/day) which shorten the schedule by 10 days for a combined cost of $1000 per day or a total of $10000. The crashed schedule has now 105 days of duration (figure 12), 35 days shorter than the original schedule, for an increased cost of $13,300 giving a total project cost of $61,600. A 105 B C D E 15 30 20 40 F 50 Figure 12. Network after three steps of compression (taken from Callahan et al. 1992, pp. 267) 107

Total project cost analysis The costs used to determine the cost-duration relationship for each activity consider only the direct costs for performing those activities. However, total project costs include direct costs and indirect costs. As seen in the example, direct costs are inversely related to project duration, thus direct costs decrease when project duration increases, and vice versa. Conversely, indirect costs increase with project duration. Indirect costs usually increase faster at the beginning of the project, and then remain constant over the course of the project. For crashing purposes, the usual assumption is that there is a relatively constant indirect cost profile for a project. The indirect cost profile is shown in figure 13 as a linear function. The slope of the line is the value of the constant indirect profile (Callahan et al. 1992). Indirect costs ($) Project duration (days) Figure 13. Duration-indirect cost relationship (taken from Callahan et al. 1992, pp. 269) The same example will be used to illustrate how to include indirect costs into the crashed schedule. Indirect costs for the project shown in figure 9 include job overhead of $250 per day throughout the project, additional support services which cost $100 per day from day 20 to day 90, and general overhead related to the staffing size of the project and duration of $150 per day. The cost profile for indirect costs must be developed first. The indirect cost profile includes two parts. The fist part consists of the constant piece of the indirect costs which include the job overhead ($250/day) and the general overhead ($150/day) for a total of $400 per day. The second portion consists of the additional support services from day 20 to day 90 with an additional cost of $100 per day. Figure 14 shows the profile for the total indirect costs which is obtained by adding both the constant and variable portions of the indirect costs. Finally a cost profile for total costs is generated by adding direct and indirect costs as illustrated in figure 15. The minimum-cost point represents the optimum duration-cost schedule. Table 5 lists the total direct and indirect costs for the several possible durations. 108

Indirect cost ($/day) Constant indirect costs Variable indirect costs MD Time (calendar days) PD (Minimum (Project duration) duration) Figure 14. Indirect cost-time relationship (taken from Callahan et al. 1992, pp. 269) Total cost ($) 120.000 116.000 112.000 108.000 104.000 100.000 196.000 100 105 110 120 130 140 Duration (days) Figure 15. Total cost profile (taken from Callahan et al. 1992, pp. 271) Project Project Project Total duration direct indirect cost (days) cost cost 140 $48,300 $63,000 $111,300 130 $48,900 $59,000 $107,900 120 $50,100 $55,000 $105,100 115 $51,600 $53,000 $104,600 105 $61,600 $49,000 $110,600 Table 5. Total project costs (taken from Callahan et al. 1992, pp. 272) 109

c. Advantages The use of any extended workdays, multiple shifts, overmanning, or the use of larger or more productive equipment, the use of materials with faster installation methods, and alternate construction methods or sequences present great potential for the construction manager to accelerate the progress of construction and reduce overall project delivery time. However, the construction manager should select the appropriate approach to accelerate the schedule considering the different advantages and benefits that each technique may offer to the particular project under construction. The use of overtime to reduce project schedule is sometimes chosen over additional work shifts and overmanning because it can produce a higher rate of progress without the coordination problems involved in managing additional crafts of workers (Hanna et al. 2005). Overtime requires workers to work extended periods of time, nevertheless, it does not require the implementation of additional craftspeople. In consequence, it can be preferred over work shift and overmanning when obtaining extra labor is not desired or is not a viable option. On the other hand, second shifts are occasionally selected over overtime because they do not present the same degree of inefficiencies from physical fatigue caused by working extended scheduled hours. In addition, the cost of additional shifts is typically lower than that of overtime. The use of additional shifts is also advantageous in accelerating activity progress while minimizing the congestion problems associated with overmanning. Some research support that the use of various work shifts may generate competition between shifts that can actually increase overall productivity (Horner and Talhouni 1995, Hanna et al. 2005). The advantage of overmanning over overtime is that higher production rates may be achieved because workers do not experience the fatigue problems associated with overtime. Overmanning may also be preferred instead of shift work to avoid the coordination problems experienced with working different shifts. Finally, the use of larger or faster equipment, alternate construction methods or sequences, and materials with faster installation methods offers substantial opportunities for improving efficiency and activities duration without the risk of losing labor productivity. d. Key elements to ensure a high degree of success Most available research findings suggest a large inverse relationship between productivity and scheduled overtime. Thus, in the first few weeks of scheduled overtime total productivity can be higher than the productivity achieved in a regular 40-hour week. However, after several weeks of overtime work, it is very unlikely to attain the same levels of productivity, and it will continue to decrease as overtime schedule continues. Therefore, as part of the schedule acceleration technique, the use of overtime should be considered for no more than three or four weeks (Hanna et al 2005). Management support is also another element that has strong impacts in the success of overtime implementation. Because it is expected that overtime schedules will lead to loss of productivity, effective management control is crucial to detect how much improvement in progress rates can be achieved by extending work days, and when the adverse effects of working overtime begin to affect labor productivity. Finally, other management supports such as engineering and design support, material availability, and supervision are also important factors that can help mitigate 110

the potential negative effects that scheduled overtime may have in productivity and labor performance. Management support and supervision is also important to successfully achieve project schedule reduction through the use of work shifts. The following management techniques can help reduce productivity losses and improve the performance of labor working additional shifts (Hanna et al. 2005): o Overlapping management: Management should overlap both shifts with the objective of making the arriving crews aware of the work that has been completed by the previous crews. One way to achieve this is by requiring the foreman of the first shift to stay 1 or 2 hours longer and the foreman from the previous shift to arrive 1 or 2 hours earlier. o Selection of work assigned to a second shift: Assigning completely different tasks to the second shift or third shift can improve work performance. This can include assigning independent tasks from the previous shifts that involve different materials and tools. o Be selective on the work assigned to a second shift: Because of the reduced availability of management and engineering support, it is recommended to assign the second shift tasks that do not require much engineering and design support, and relatively small scope of work. A smaller scope allows improved coordination, planning, and supervision of the second shift. o Material requirements: Management should anticipate the material requirements of the tasks assigned to the second and third shifts, and if possible assign tasks that require the minimum material requirements, to enhance high performance of second shifts. o Avoid congestion: The use of different work shifts is more effective when the implementation of overtime or additional craftsmen and trades can generate increased congestion. o Sufficient amount of artificial lighting: Providing night shifts with sufficient artificial lightning is essential to enable shifts perform efficiently and to enhance safety. Overmanning s intentions of reducing project duration, on the other side, can be enhanced through the availability of adequate work space to accommodate the increased number of workers at the job site. The loss of productivity involved with overmanning can also be minimized by adopting skilled labor and increased, resourceful and well-organized supervision. e. Disadvantages Scheduling extended hours to reduce the duration it takes to complete activities and therefore shorten construction delivery time involves several important factors that have to be taken into consideration. Extending workers working hours require employers to pay an overtime rate which is typically 1.5 times the normal wage for any work beyond 8 hours per day, and it can go up to 2 times the normal wage, particularly if overtime is scheduled in weekends. In addition, the extended work hours generated by scheduled overtime include other extra costs for support services. All these additional costs have to be considered in the cost-duration trade-off analysis to decide to what extent and at what cost the construction manager is willing to accelerate the project (Callahan et al. 1992). Labor productivity can also be negatively affected when overtime is implemented to accelerate the project, particularly when overtime is scheduled for several weeks. Overtime is an indirect factor that has the potential to cause disruptions in the work environment. By itself, overtime 111

does not lead to productivity loss; however, it can activate other factors that can lead to poor and inefficient productivity. For example, the construction or project manager decides to accelerate the progress of certain activities by extending weekly work hours from four 10-h days to six 10- h days. Labor work hours are therefore increased by 50%. In theory, to maintain workflow and work efficiency to finish the work earlier the entire system should respond to the increase in work hours. Thus, materials should be made available 50% faster, tools and equipment should be used 50% more, information also has to be made available faster, project staff support should also increase, and so on. However, that rarely happens, and the lack of resources (materials, equipment, tools and information) or mismatch between the demand of work from increased labor and the availability of resources to support increased demand can result into recurrent interruptions which adversely affect labor productivity and work efficiency. Thomas and Raynar suggest that, on average, interruptions caused by overtime cause short-time productivity losses of about 10 to 15 percent (Thomas and Raynar 1997). In addition, projects that are already behind schedule or experience disruptions caused by other factors, such as incomplete design, numerous changes, etc., are more likely to experience greater losses in productivity. Similar studies suggest that it is possible to work overtime for three or four weeks without losses of productivity; however the likelihood is very small (Thomas and Raynar 1997). Overtime scheduled to last for more than a few weeks will result into productivity losses caused not only by interruptions but also by mental and physical fatigue. Research also suggests that there is a direct relationship between the number of work days per week and the level of productivity loss. When the work days per week increase over regular schedule, it is more difficult to provide labor with resources at an accelerated rate, leading to increased interruptions with a negative effect in productivity (Thomas and Raynar 1997). Other problems associated to overtime and the resultant productivity loss include mental and physical fatigue, increased accident rates and reduced safety, increased absenteeism and low morale (Hanna et al. 2005). Finally, according to the U.S. Army Corps of Engineers, when the hours of work increase workers tend to pace themselves for the extended day or week, thus they adjust their pace to accomplish about the same amount of work in an extended workday or workweek as what they would accomplish in a straight time workday (U.S. Army Corps of Engineers 1979). All the problems introduced by scheduled overtime reduce productivity and increase the cost of construction. Hanna et al. suggest that the premium cost of overtime and the reduced labor productivity result in a combined increased hourly cost of an average of 300 percent more than the normal straight time hourly rate (Hanna et al. 2005). Working multiple shifts also introduce additional costs to the project including additional administration personnel, supervision, quality control, safety, and support services such as lighting, hence the cost of operating under multiple shift works is higher than operating under normal circumstances. Other problem associated with working additional shifts is that there is no single point of responsibility for progress and quality. Sometimes it is also necessary to have periods of overlap between shifts to smooth the changeover. The changeover among shifts requires extensive coordination due to little communication and cooperation between shifts and inconsistent operating procedures across shifts. Performance of shifts can also be hindered by the unavailability of timely administrative decisions because of the absence of management support 112

in hours other than business hours (Penkala 1997, Hanna et al. 2005). A major problem involved with working additional shift work is the impact it has on workers sleeping patterns and the problems associated to getting the body adjusted to the new schedule and cycle. Studies show that it takes around 7 to 12 days to get the body used to a new work and sleep cycle (Costa 1996, Hanna et al. 2005). Other studies suggest that 24 to 30 days are needed to achieve the same levels of performance (Fly 1980, Hanna et al. 2005). Working in different schedules can have important impacts in workers performance as well as in their health. Workers that work at night usually have less hours of sleep than workers working during the day, which can lead to lower levels of performance. Additionally, the changes in laborer s internal work and sleeping cycles may affect important processes such as motivation, alertness, and judgment (Hanna et al. 2005). All these consequences can lead to loss of labor productivity. Work safety is another important factor that can be affected by working multiple shifts. The sleeping shortage experienced by labor working night shifts and the related effects in workers alertness and judgment, along with the associated physical fatigue can lead to increased rates of accidents and reduced safety. Moreover, during second shifts, supervision and management support is reduced, which along with the poor conditions of work such as poor lighting, can also have a negative effect in workers performance and safety. Research indicates that work performed by night shifts usually produce more errors and accidents (Costa 1996, Hanna et al. 2005). The major disadvantages associated to the use of increased number of workers include inefficiencies related to physical conflict, high density of labor, and congestion. Efficient management and supervision can also be impeded because of the enlarged amount of craftspeople. In addition, the demand for engineering questions and requests for clarification can also increase with the likelihood of not been responded in a timely manner. The availability of materials, equipment and tools may be deficient as well due to the increased number of workers, hindering efficient productivity. The need for large amounts of labor may bring in less productive workers impacting overall productivity. Lastly, the major disadvantage of bringing into play larger or faster equipment, materials with faster installation methods, and alternate construction methods or sequences is that although these enable dramatic reductions in project duration, the increase in project costs are typically dramatically elevated. f. Applicability and use Determining which technique is the best to adopt to successfully accelerate the progress of construction requires knowledge and experience of the construction manager, and careful analysis and planning. Once the most appropriate and suitable approach for increasing the progress rates of activities has been selected, the difficulties involved in accelerating a project by crashing the activities in the schedule are not in the application of the technique itself but rather in determining how much each individual activity can be reduced and the cost of this reduction. Determining how much an activity can be reduced and the cost of reduction also requires experience and knowledge not only in scheduling but in cost estimating too. Knowledge and experience can also aid the construction manager or project scheduler to know intuitively which activities can be reduced and how far these can be reduced at the least cost. 113

IV. Summary Construction management is the practice of professional management services targeted to the planning, design and construction of a project aiming at improving project s performance in the best interest of the owner. Construction management professional services can by applied under any delivery method either in an agency basis or through construction management at risk as a separate delivery system. Through both approaches, the Construction Manager can support owners by using effective strategies to enhance project planning and management, and deliver to the owner better projects, on time and within budget. However, controlling costs and schedule overruns in construction projects with their associated aggressive schedules and budget limits present construction managers with challenges that are further augmented when the project schedule has to be further accelerated (Mashalen and Chasey 1999). Various schedule acceleration techniques that allow the construction manager to better control project time and accelerate schedules in order to reduce project delivery cycles have been recompiled within this document. These schedule acceleration techniques can be applied by the Construction Manager depending on the project delivery method adopted. Some of these techniques are simply good management practices which can be applied to every project under any circumstances to improve overall performance including schedule performance. Others are techniques commonly applied within the industry in situations where project completion needs to be accelerated for different reasons. Innovative techniques that are relatively new to construction are also gaining acceptance because of their proven results in terms of project performance and time. Each technique has its individual characteristics in terms of potential advantages to project success and disadvantages or trade-offs that they may entail. Different techniques may also have different levels of applicability and influential factors that can lead to a successful implementation. Overall, three main concepts stand out in most if not all techniques. First, planning has proven to be a key in allowing effective implementations and results from schedule compression techniques. Second, an environment of teamwork facilitated by management support establishes adequate grounds for properly performing under environments of acceleration and schedule pressures. Finally, systems that enhance efficient communication are core for enabling good planning and teamwork, and consequently, driving any intention of schedule acceleration to succeed. 114

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