Developing Critical Path Method Scheduling (CPM)

Transcription

1 Developing Critical Path Method Scheduling (CPM)

2 Pretest 1. An activity which is on critical path has a planned duration of 5 days. What is the total float for the activity? a. 0 b. 1 c. 2 d. 3

3 Pretest 2. Which is not a widely recognized type of scheduling method? a. CPM b. Linear c. Vertical d. Bar

4 Pretest 3. Which of the following is directly affected by project scheduling? a. Time b. Cost c. Work Flow d. Man Power e. All of the above

5 Pretest 4. Of the three (3) main scheduling methods, which one uses relationships between activities? a) Linear b) CPM c) Bar

6 Pretest 5. Which scheduling method is the most commonly practiced? a) Bar b) Vertical c) Linear d) CPM

7 Pretest 6. Total Float is the amount of time an activity can be delayed without delaying completion date of the project. a) True b) False

8 Pretest 7. TheWork Breakdown Structure (WBS) shouldbe used for identifying the activities and for organizing the schedule. a) True b) False

9 Pretest 8. Which of the following should be used in determining activity durations? a) Historical Data b) Manuals c) Experience d) Field recommendations e) Allof the above

10 Pretest 10. Who should do project scheduling? a) Project Manager b) Owner c) Superintendent d) All of the above

11 Pretest 9. There isalwaysmorethanonecorrect one logicfor completion of a project. a) True b) False

12 Purpose and Background for Construction Schedules Determine reasonable and accurate contract time for construction Contract time is the maximum time allowed in the contract for completion of all work contained in the contract documents. Project Scheduling is the process of: Identifying the activities necessary to complete the project Assigning realistic durations to each activity Establishing start and finish dates for each activity

13 What Does a Schedule Do? Helps the owners in planning during the development of the project Public Notifications Road Closures Construction sequencing, phasing & milestones Alternate bid schedules Tool for comparison

14 Effects of Insufficient Contract Time Bid prices may be higher Unusual number of time overruns Contractor Claims Missed milestones

15 Effects of Excessive Contract Time Cost inefficiencies by the contractor Public may be inconvenienced unnecessarily Travel on unsafe roadways for and extended period of time * If the time set is such that all work on a project may be stopped for an extended periodand the contractor can still complete the project on schedule time allowed was excessive

16 Schedule Guidelines When shouldyou create your first schedule? Schematic Drawings 30% Design Development 50% Submittal Drawings 90% Update the schedule for all PS&E submittals

17 Determining Contract Time Production Rate What is Production Rate? The quantity produced or constructed over a specific time period. Why is this important? Helps determine appropriate completion time. Production rates may vary considerably depending di on project size, location and setting.

18 Determining Contract Time Production Rate Establishing Production Rates Divide the total quantity of an item by the number of days/hours used to complete the item. Base production rates upon a 5 day work week/ 8hr crew days/ our per piece of equipment Historic data DOT data RSMeans Cost Data books

19 Hot Asphalt Concrete Pavement Production Rate: HACP Paving (max) 1,980 tons/day HACP Paving (min) 1,320 tons/day Starting Rate = ( )/2 = 1,650 tons/day (8 hour day) Projects Specifics: Cold Temps Remote Location

20 Other Factors Affecting Contract Times Effects of Traffic Curing Times / waiting periods between paving courses Setup/mobilization/special equipment Seasonal Limitations Conflicting Operations Submittal review Times Fabrication Times Lead times Long lead Items Holidays Number of Crews/crew Size Environmental Temporary construction Soils

21 Steps for Creating CPM Schedules Define the Work Day Define the Project Calendar & Task Calendar Identify, Group and Sequence the Activities iii Set activity Durations Link Activities Documentation Update

22 Defining the Work Day Work hours establish the daily work times. Standard work day is an 8 hour day.

23 Defining the Project Calendar Defines project s work and non work days Saturdays, Sundays, Holidays Other Contractual non work days Local Events Task Calendars define work that can only be performed at a specific time and date.

24 Activities A key factor in any realistic schedule is to include the right activities. Consider each project as unique. Break project scope into individual id activities iti Work Breakdown Structure (WBS) should be used for identifying the activities and for organizing the schedule The number of activities depends upon the complexity of the project Once Activities are identified and grouped, determine the general sequencing of the activities.

25 Staking Typical Activity Inclusions & Exclusions Only show staking tasks that are necessary to start the project (e.g., clearing limits and slope stakes). Clearing & Grubbing Show only work needed to begin major activities Erosion Control In place items before major grading operations Earthwork Break out rock excavation asa a separate activity

26 Typical Activity Inclusions & Exclusions Pavement Structure Items Combine associated items as one work activity Separate major structure items such as; base course and asphalt Bridge Activities Show by phase of construction foundation, substructure, superstructure Sub Excavation Combine into one activity it Drainage Show individual culverts

27 Typical Activity Inclusions & Turf Establishment Show as one item Signage & Striping Exclusions Combine all permanent traffic control signing and striping into one activity. Guardrail Combine into one activity

28 Activity Durations Setting durations is a critical step to creating a reasonable schedule. Factors effecting time should be taken into consideration. Adjust activity ii durations based on production rates. Try and limit the duration for any activity to 20 days.

29 Link Activities Determine activity relationships Late Finish (LF): The latest time an activity can be finished. Late Start (LS): The latest time an activity can be started without delaying completion of the project. LS = LF D Total Float: The amount of time an activity can be delayed without delaying completion date of the project. TF = LF EF + LS ES Free Float: The amount of time an activity can be delayed without delaying early start time of the following activity Critical Path: A series of connected activities with each activity having zero float (free, and total) time.

30 Link Activities The order in which activities will be performed is called logic How one activity relates to another activity is called logical relation Finish to Start Finish to Finish Start to Start Defining proper logic requires understanding of the project There is always more than one correct logic for completion of a project.

31 Documentation Document any assumptions: Production rates Equipment Types Quantities Crews Follow the logic

32 Update A Schedule is only a tool!

33 Check List Reviews/Submittals Are there critical submittals? What Time is needed? Are there critical testing periods & how long? Are there critical review times & how long? What are the assigned calendars for submittals & review times? What are the logical connections between review activities and contractor s actual work? Procurement activities Time for reviewing false work plans, shop drawings, post tensioning plans, mix designs, etc.

34 Check List Permits Are permits required? Time to obtain necessary permits?

35 Check List Specific Activity Requirements Additional time for obtaining specialty items or materials with long lead requirements (i.e. Traffic Signal Equipment) Curing time and waiting periods between successive paving courses or between concrete operations Embankment settlement periods orembankment surcharges. Coordination with Utilities False work & Shoring activities Punch list and cleanup activities

36 Check List Material/Product Testing and Delays Government/Owner furnished material Trial shafts or piles Sample walls Time of fabrication fbi of structural t steel and other specialty items Staining, painting or other samples needing approvals

37 Check List Construction Limitations and Requirements Haul characteristics Type of earthwork (sliver cuts, benching) Work area restrictions Equipment congestion Allowable bad weather days Material availability Labor shortages and resource loading Traffic Volumes Traffic staging events (closures, detours) Critical interface activities (utilities, RR) Restrictions for nighttime and weekend operations Conflicting operations of adjacent projects, both public and private Are the NTP and Project Closeout activities shown?

38 Check List Project Commitments ts Environmental Commitments Winter season Clearing, grubbing, grading restrictions Noise restriction SWPPP Seasonal limitations for certain activities Project Calendar Requirements Work kweek Holidays Other non working times

39 Check List Does the final schedule include/show: Critical Path? NTP date and completion date Entire scope of work, all activities in plans and specs? Construction Staging and mobilization? Realistic duration of individual activities? Maximum 20 day duration for any one activity? Activities have at least one predecessor and 1 successor? No negative lag for activities/ Project Duration, Interim Milestones, Black out dates, contract work days?