PROGRAMMING CPM. Network Analysis. Goal:

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1 PROGRAMMING CPM 5/21/13 Network Analysis Goal: Calculate completion time Calculate start and finish date for each activity Identify critical activities Identify requirements and flows of resources (materials, labour, equipment, $$$) 1

2 Network Analysis Programme Evaluation Review Technique (PERT) Monte Carlo Simulation Line-of-Balance (LOB) Location-based Scheduling (LBS) Deterministic analysis: Shortest completion time For each activity: n Earliest and latest start dates (ES and LS) and consequently Earliest and latest finish dates (EF and LF) n Float (F) available Critical Path 2

3 Gives: Shortest completion time For each activity: n Earliest and latest start dates (ES and LS) and consequently Earliest and latest finish dates (EF and LF) n Float (F) available Critical Path Assumes: For each activity: n Fixed duration n Well-defined precedence relations 3

4 Activity-oriented Activity-on-Node representation is preferred 4

5 ID Activity Predecessor A Site Clearance - B Grading general area A C Excavation utility trenches B D Excavation foundations B E Placing formworks D F Placing reinforcements E G Installing sewer lines C H Installing other utilities C I Pouring concrete F J Remove formworks I (Lag = 4days) K Refill utility trenches G,H L Refill foundations J M Cleanup K,L 5

6 n Forward pass n Forward pass 6

7 n Forward pass Earliest completion date 3. Calculate LS & LF for each activity Total Float (TF) n Backward pass 7

8 3. Calculate LS & LF for each activity Total Float (TF) n Backward pass Activity Float: Total Float (TF): TF = LF LS LF n TF>0 Programming Flexibility: ES D ES EF n As long as the activity does not start before ES and does not finish after LF, the project earliest completion date remains unchanged: n For the same D, S can be delay up to TF days n For the same ES, D can be increased by up to TF days n A combination of the two above. 8

9 Activity Float: Total Float (TF): TF LF LS LF n TF>0 Programming Flexibility: = ES D ES EF n TF = 0 No programming Flexibility Critical Activity 3. Calculate LS & LF for each activity Total Float (TF) n Backward pass 9

10 3. Calculate LS & LF for each activity Total Float (TF) 4. Identify Critical Path 3. Calculate LS & LF for each activity Total Float (TF) 4. Identify Critical Path 10

11 3. Calculate LS & LF for each activity Total Float (TF) 4. Identify Critical Path Activity Float: Total Float (TF): Free Float (FF): FF Earliest of the ES of all successors Latest of the EF of all predecessors ES = successors ES EF successors predecessors EF D n = Delay that can be assigned to an activity without impacting the start time of all its successors. 11

12 Activity Float: Total Float (TF): Free Float (FF): Independent Float (IF): Earliest of the ES of all successors Latest of the LF of all predecessors IF = max( ES LF D;0) successors predecessors n = Float in «worst case situation» n = Float that cannot be used by any other activity n Rarely used. Activity Float: Total Float (TF): Free Float (FF): TF = LF ES D FF = ES EF Independent Float (IF): IF = max( ES LF D;0) succ succ predec D predec 12

13 Activity Float: ID Activity FF IF TF A Site Clearance B Grading general area C Excavation utility trenches D Excavation foundations E Placing formworks F Placing reinforcements G Installing sewer lines H Installing other utilities I Pouring concrete J Remove formworks K Refill utility trenches L Refill foundations M Cleanup Activity Float: 0 IF FF TF TF = 0 ( = FF = IF) OnCriticalPath TF is most commonly used But: A lot of float is shared between consecutive activities! 13

14 (Linked) Gantt/bar Chart Task Description (Name, Duration, Predec., Start / End, etc.) Calendar Non-linked: Activity defined by Start Date + Duration Linked: Activitiy defined by Predecessors + Duration n Automated calculation of ES, EF, LS, LF, TF(, FF, IF), Critical Path 14

15 Advantage: Calendar (+ holidays ) n Dates as opposed to days Communication Aggregation: WBS Standard types of activities n SMM7 (UK), CSI s Masterformat (USA), ASTM s Uniformat (USA) Spatial divisions 15

4. Network Calculations

Construction Project Management (CE 110401346) 4. Network Calculations Dr. Khaled Hyari Department of Civil Engineering Hashemite University Calculations On a Precedence Network I Early Activity Start