Successful Implementation Of Design Assist On A Large California Hospital Project

Transcription

1 Successful Implementation Of Design Assist On A Large California Hospital Project Maroun N. Zeidan & Mark A. Hershberg, Associates Aaron D. Reynolds, Principal John R. Gavan, Managing Principal KPFF Consulting Engineers Los Angeles, California Robert Hazleton, Vice President Tom Kuznik, Chief Engineer Raul Nazareno, Project Engineer The Herrick Corporation Stockton, California Abstract In the past few years, Design Assist has become one of the more popular project delivery methods (PDM). Design Assist consists of involving the contractor and key sub-contractors early in design to provide input in order to make the design more efficient and to streamline the construction process. The integrated approach early in design by the design team and the contractor helps reduce the risk of miscommunication that often leads to design inefficiency, costly redesign or construction errors. This paper presents the successful implementation of the design assist process as it relates to structural steel on the Palomar Medical Center (PMC), West hospital in Escondido, CA. The hospital is a twelve-story steel building with partial basement. The total area is approximately 750,000 ft 2. The building consists of many unique and complex areas such as a wavy-shaped green roof supported on 105 feet long -span trusses above operating rooms as well as heavily loaded healing gardens/terraces with long span cantilevers at the nursing tower. The rigorous state approval process for hospitals in California, as well the complexity of this project, made design assist even more compelling. Bi-weekly face-to-face team meetings and countless s were used to discuss framing and detailing of unique areas of the building. These meetings happened in a collaborative and interactive environment. The project team s chemistry, level of trust, as well as their commitment and creativity, led to the success of the design assist PDM on this project. The use of Building Information Modeling (BIM) also facilitated the identification of complex details that required input by the steel subcontractor. The success of the structural steel design assist process on this project resulted in a more efficient design that reduced cost and accelerated schedule. The steel structure was completed with a savings of 7.2 million dollars out of the originally estimated budget of $52.8 million, and the original 13 months schedule was reduced by 6 weeks. In addition, the project was completed with zero change orders and cut the RFI s by an estimated factor of four. Introduction In California, design-bid-build has been the conventional and the most common project delivery method used on hospitals. One of the main potential problems associated with this delivery method is that by the time the contractor is brought to the project, post design, there is little opportunity to provide input on the design. Failure to do so often results in reduced productivity leading to cost overruns and extended construction schedule. On the project mentioned later, the innovation lies in integrating key subcontractors early into the design process to understand the project, its intent, and to help in optimizing project results from design and fabrication through construction. As discussed above, the structural steel design assist process has proven to be very successful on this job and has resulted in a steel cost savings and schedule reduction.

2 This paper will highlight this process and list a few examples that were discussed. Project Information and General Description The Project under consideration is the Palomar Medical Center, West located in Escondido, California lwhich is in Northern San Diego County (See Figure 1). The new hospital facility will include 360 beds and will replace the acute-care services at the present Palomar Medical Center in Escondido. It consists of a three-story Diagnostic and Treatment (D&T) podium base with a patient room Tower over the north part of the podium (See Figure 2). The hospital is projected to be completed in The hospital features many state of the art design features such as decentralized nursing stations, acuity adaptable rooms, healing gardens and green roofs. For Palomar West, sustainable healthcare was defined as a high performing hospital in which nature coexists with and is enhanced by technology. The project s design target LEED certification is Gold. Sustainability was a design consideration in every aspect of the design from water and energy efficiency, to envelope and structural design. The gravity system consists of concrete filled metal deck supported on steel beams, girders and columns. The lateral force resisting system consists of special steel moment frames using the proprietary SidePlate system from level one to roof, and concrete shear walls in the one-story partial basement under the patient room tower and the east part of the D&T. Hospitals in California undergo a rigorous review by the Office of Statewide Health Planning and Development (OSHPD) to ensure public safety and continuous operation of acute care and inpatient facilities after an earthquake. The review and approval process includes the initial design permit drawings as well as any future changes post approval and during construction. The unique features of this project, the effect of their design on the economics and schedule of the project, as well as the review process, made it an ideal candidate for design assist. On this project, the construction manager and key contractors, such as concrete, steel, and curtain wall trades have been incorporated early in the design to streamline the construction process. The following paragraphs discuss the design assist process as it relates to structural steel as well as the successful implementation and benefits of this process. Structural Steel Design Assist Process the structural engineer (KPFF Consulting Engineers), the construction managers (Rudolph & Sletten and DPR Construction), the steel contractor (The Herrick Corporation) and the architect (CO Architects). The process molded design considerations with means and methods concerns. Biweekly face-to-face meetings and countless s were used to discuss framing, sequencing, and detailing options for different areas of the building during the design process. Electronic sketches derived from the Revit BIM model, as well as hand sketches were continuously exchanged between team members during the design progress. The team members would then sketch up and scrutinize different options on a white board before deciding on a final design that will benefit the project in regards to cost, schedule, and sustainability. At the end of every design milestone, the design team would submit a copy of the progress drawing set to the contractor in order to collect overall feedback on the design and address any concerns. In the design assist process, feedback and discussion of the design is interactive and happens during the design process as opposed to a conventional design-bid-build process where the contractor s feedback is post design; often resulting in change orders to the drawings and creating major inefficiencies related the approval and schedule of the project. Areas addressed and benefits to the job. Though many of the items addressed during the design assist process were related to detailing the unique areas and features of the building, other less obvious aspects of the construction effort were addressed in the design assist process. These aspects, including job sequencing, transportation, and safety, can significantly impact the cost and schedule with traditional project delivery methods. Below is a description of the relevant design assist discussions and their benefits to the project. The diagnostic and treatment wing s wavy roof was one of the most rigorously discussed areas of the building due to its multiple functions and location. The roof is used as an undulating architectural feature supporting a green roof system. It also supports the MEP systems feeding the operating and imaging rooms on level 2 below, and it is intended to provide future remodeling flexibility in the operating rooms area by providing a column free zone 105 feet wide by 303 feet long. The roof undulates at about 22 feet to 32 feet above level 2, which necessitates an interstitial support at the operating rooms ceiling level to support secondary MEP systems, medical gas, overhead medical equipment, and ceilings. Process description. Structural design assist on PMC West was a very interactive and collaborative team effort between

3 Figure 1. Project Location Patient Tower Healing Gardens with trees and planting on 3 sides of the building and on the roof Outdoor terrace with trees and planting Courtyards with trees and planting Diagnostic and Treatment block with wavy green roof Figure 2. Project description

4 Figure 3. Two-way truss (left) versus One-way truss (right) systems The preliminary structural design consisted of 105 feet long trusses at about 34-6 on center with secondary sub-trusses at about 11 feet on center spanning between the main trusses. The trusses bottom chords occurred at the same elevation above level 2 and served as the interstitial space while the top chords followed the roof curvature. Trusses fabrication, transportation, and erection were also discussed. The complexity of the two way truss system and its intense demand for field labor was carefully evaluated. The design assist team decided to eliminate the sub-trusses diagonals and turn this roof into a one-way truss system with top and bottom purlins at 11 feet on center (See Figure 3). The goal was to try and shift as many of the field hours to the shop, simplifying the tasks to be performed in the field, thus optimizing transportation to the site. Truss depths varying from about 12 to 22 feet posed a transportation challenge. Many discussions related to the truss end connections, allowable truss splice locations and possible truss vertical and diagonal member connections led to the decision that the trusses would be bolted together in the field. The top purlins curvature was also discussed. Two-way transportation of the members from the fabrication facility to the curving facility and back as well as the time impact associated with it, was weighed by the steel subcontractor. The decision was to segment the beams instead of curving them and make up the small difference between the straight segments and the desired curvature with up to 2 inches of added concrete. The final design saved about $2 million dollars in material and field labor, and helped speed up construction (See Figure 4) Partial view of D&T wavy roof Bolted connections Figure 4. Wavy roof (left) - One-way truss and purlins (right)

5 Restroom cantilevers Figure 5. Patient tower restrooms The patient rooms restrooms were also carefully evaluated during design assist meetings. The importance of the restroom framing lies in the number of times it occurs; about 360. The patient tower has a long and relatively narrow footprint with patient rooms located along the longer edges. Triangularshaped restrooms cantilever off of the perimeter framing forming saw-toothed edges (See Figure 5). The use of an end plate connection for the cantilever and back span at every other restroom is self supporting and self aligning so it eliminated the need for temporary posts that would have been required to support the tip of the cantilevers until welding was complete. The intermediate restroom framing was shop attached to the edge beam and installed as one piece in the field (See Figure 6). These innovative ideas eliminated 360 complete penetration joints and transferred hours from the field to the shop making steel erection easier, faster, more cost effective and most importantly, safer. Intermediate restroom shop attached to edge beam Edge beam Endplate connection Figure 6. Partial restroom view

6 Figure 7. Terrace and Conservatory Terraces and conservatory framing is another design feature that required extensive effort and collaboration among team members. These significant architectural features were closely coordinated with the architect to ensure that detailing decisions were in line with the desired aesthetics. The terraces are on this project are staggered balconies on the east and west ends as well as the central south side of the tower. Each of these terraces supports trees and/or heavy planting and is enclosed by a glazing. The central terrace has a conservatory feature cantilevering above the last floor. HSSRectangular Hollow Structural Sections (HSS)were used to support the screen and to cantilever above the roof and frame the conservatory element (See Figure 7). The main challenge with the terraces HSS framing was integrating the design with means and methods. The design challenges were vertical deflections of the terraces due to the heavy soil and planting load, temperature gradient, and wind loading on the conservatory. The contractor s involvement in the design and their understanding of the design challenges as well as the design team s understanding of the erection sequence resulted in a solution to the challenges mentioned above. After numerous meetings and discussions, the conservatory sketches from the white board were developed into the construction documents (See Figure 8). The team decided to allow vertical deflections at every other connection of the vertical HSS to the terrace framing. A malefemale pin connection with vertical gap was also introduced in the vertical HSS just above the connection to the terrace to allow for vertical slip. The pin connection allows for temperature deformations while providing out-of-plane vertical tube continuity to resist wind loads. The conservatory framing was laterally tied to the building s roof and cantilevered up to 20 feet. Design assist was crucial to the successful design and construction of this portion of the building. Job sequencing and appropriate detailing in order to minimize overlap between steel and concrete scopes was another good idea resulting from the design assist process. There were many discussions about detailing gravity and moment frame column base plates, moment frame grade beams and encasement, and SidePlate connections in a way to minimize coordination effort between concrete and steel trades in the field. This accelerated the construction schedule. Coordination of multidisciplinary items that often result in expensive change orders and field fixes were also addressed by the design assist process on this project. Elevator guiderail support HSS and edge of slab closure plates are two big ticket coordination items that often require redesign and rework during construction due to the lack of input from relevant subcontractors. Early collaboration between the design team and subcontractors (exterior wall, steel, mechanical and decking) allowed the team to identify the scope, location, and extent of steel and gage closure plates along the perimeter and interior openings of the building. Similarly, collaboration with the steel and the elevator subcontractors during design enabled the team to properly

7 Figure 8. White board to drawings locate the elevator guide rail support HSS. These two items have been successfully installed without any need for field rework, which benefited the schedule. Transportation of steel members was a valuable topic of discussion in design assist meetings since it is rarely wellconsidered in design. The proposed built-up moment frame columns and the heavy moment frame beam-column trees posed a real transportation challenge due to their width and weight. The fabrication cost of built up members is also considerably higher than rolled members. Transportation and fabrication cost created additional incentive for the design team to consider a voluntary code change from the 2001 California Building Code (CBC) to the 2007 CBC code. The code change resulted in a reduced base shear and thus reduced lateral force resisting system tonnage and enabled rolled sections to be used exclusively for the frame columns, eliminating the need for built-up columns on the job. The smaller, lighter sections also facilitated the transportation of the beam-column trees to the jobsite. The steel tonnage savings from the code switch was about 800 tons. Sustainability was a constant consideration during design assist discussions especially since the design team targeted a Gold LEED Certification for this project. The elimination of sub-trusses, the code switch, and the use of rolled column sections had a significant effect on reducing overall steel tonnages. This also optimized the use of recycled steel. The code switch alone saved about 800 tons of steel which would have emitted 1200 tons of CO2 into the atmosphere. It also helped change built up members to rolled sections and minimized the steel shipped from outside the country. Local rolled steel is mainly recycled scrap. Steel from recycled scrap reduces CO2 emissions by half when compared to steel from iron ore. The design assist process was successfully used on this project and resulted in major benefits to the steel cost and schedule. The above mentioned creative solutions were a result of a collaborative and interactive effort of all the team members. The size of this project, its geometry and complicated features as well as the hospital approval process in California, made the design assist process the smart and efficient project delivery method. This project could not have had such a positive outcome if the design team members were performing their design without any input from contractors. This collaborative process resulted in an estimated $1.5 million in material savings, $1.8 million reduction in labor cost, and $2.7 million reduction in contingency. The number of RFIs was reduced by an estimated factor of four and there were no change orders. The project was delivered 3 weeks ahead of schedule too.

8 Figure 9. 3D modeling versus Reality (Courtesy of DPR Construction) Reasons for success. Like any other project delivery method, Communication, chemistry, and a high level of trust among team members are probably the most important reasons for the success of the design assist process on this job. Team members collaborated in a guard free environment where the project s ultimate success was the only consideration. All team members were proactive and trying to solve problems every step along the way. None of the team members was trying to simplify their scope of work at the expense of the project s benefit. In some cases, design rework was made because it had positive impact to the cost and schedule of the project such as the sub-trusses elimination and the restroom cantilevers end connection. The Use of BIM facilitated the communication process and helped team members visualize the impact of the decisions made on the final design (See Figure 9). Many design assist discussions took place with the BIM model projected in the conference room or with plotted views of the model used to convey the design intent and challenges. The type of contract where the contractor assisting in the design will be performing the work is also another contributing factor to the success of the process. It adds incentive for the subcontractor to get even more engaged and be more proactive to understand the final design and make sure every effort is made to streamline construction. Keeping the big picture in mind was always a shared goal of the team when making decisions related to the design. In all cases, the focus of the effort was the best interest of the project and the owner. The team looked for opportunities to save on materials by targeting areas that presented bulk opportunities to do so while allowing marginal steel weight increases at other areas if it helped streamline steel erection by reducing the number of pieces. The team was constantly trying to find ways to have a more efficient design. Conclusion Design assist is a relatively new PDM that has significant potential benefits to a project if the basic ingredients for success exist. The integration of contractors early in the design phase helps them better understand the design documents and scope leading to a less risky job that can be more accurately priced. It also minimizes questions and costly change orders during construction. The contractor s chance to provide input during design helps shorten the construction schedule as well. The structural steel design assist on this project was very successful and resulted in cost savings and accelerated schedule. The steel structure was completed $7.2 million less than the originally estimated budget of $52.8 million. Steel was erected 3 months faster than originally anticipated and there were no structural steel change orders.

9 Figure 10. Steel topping off