Construction Project Management UP Copyrights 2008 Faculty of Applied Engineering and Urban Planning Civil Engineering Department Construction Project Management 2nd Semester 2008/2009 Project Scheduling Week ( 6 + 7 ) Lec. ( 11 + 12 + 13 + 14 ) Eng: Eyad Haddad

CH4: Project Scheduling Scheduling = Planning + Time Construction Project management functions: 1. Planning تخطيط 2. Organization تنظيم 3. Supervision مراقبه 4. Control تحكم 1. Time الوقت 2. Cost التكلفة 3. Quality الجودة 4. Performance الانجاز Scheduling Scheduling = Planning + Time Scheduling is the determination of the timing of the activities comprising the project to enable managers to execute the project in a timely manner.

CH4: Project Scheduling The project scheduling is used for: Knowing the activities timing and the project completion time. Having resources available on site in the correct time. Making correction actions if schedule shows that the plan will result in late completion. Assessing the value of penalties on project late completion. Determining the project cash flow. Evaluating the effect of change orders on the project completion time. Determining the value of project delay and the responsible parties.

4.2 The Critical Path Method (CPM) The critical path can be defined as the longest possible path through the "network" of project activities. (CPM) is the most widely technique used for scheduling, it calculates the minimum completion time for a project along with the possible start and finish times for the project activities.

4.2 The Critical Path Method (CPM) The critical path itself represents the set or sequence of activities which will take the longest time to complete. The duration of the critical path is the sum of the activities' durations along the path. Duration of the critical path represents the minimum time required to complete a project. Any delays along the critical path would delay the project. More than one critical path may be among all the project activities, so completion of the entire project could be delayed by delaying activities along any one of the critical paths.

4.2 The Critical Path Method (CPM) For example, a project consisting of two activities performed in parallel that each requires three days would have each activity critical for a completion in three days. Critical path scheduling assumes that a project has been divided into activities of fixed duration and well defined predecessor relationships. A predecessor relationship implies that one activity must come before another in the schedule

The CPM is a systematic scheduling method for a project network and involves four main steps: A forward path to determine activities early-start times; A backward path to determine activities late-finish times; Float calculations ( Free & Total ) float; and Identifying critical activities.

i j x dx 4.3.1 Activity-on-node networks calculations The objective of arrow network analysis is to compute each event in the network its early and late timings. These times are defined as Early event time (ET) is the earliest time at which an event can occur, considering the duration of preceding activities. Late event time (LT) Is the latest time at which an event can occur if the project is to be completed on schedule. 1. Forward Path: ETj = ETi + dx ETi LTi ETj LTj i j x dx

1. Forward Path: 5 d1 B 3 A A A C4 E 1 1 1 3 9 11 d=3 5 D 6 d2 7 6 3+3=6 Es+d=EF Project Start=0 Project Start=0 9+5=14 0+3=3 d1 B 3 14 3 A A A C4 E 1 1 1 3 9 11 d=3 5 D 9 6 d2 6+0=6 3+4=7 7 9 9+0=9 3+6=9

2. Backward Path LS = LF – d 9 5 d1 B 3 14 3 A C4 E 1 3 9 11 3 5 D 9 6 9-3=6 5 9-0=9 9-4=5 3-3=0 9-6=3 d1 B 3 3 14 14 3 A C4 E 1 3 9 11 3 5 D 9 9 6 d2 14-5=9 LF-d=LS 7 9 9 9-0=9

3. Float Calculations: First, let's tabulate the information we have as shown in next Table One important aspect is Total-Float (TF) calculations, which determine the flexibility of an activity to be delayed. Total Float (TF) = LF – EF = LS – ES ملاحظة : TF دوما يستخدم للنشاط الواحد. Free Float (FF) = ETj – ETi – d or FF = smallest ES (of succeeding activities) – EF (of current activity) ملاحظة : FF دوما يستخدم للنشاطين السابق واللاحق.

3. Float Calculations: Total Float (TF) = LF – EF = LS – ES j A LS LF LS LF AON AOA Free Float (FF) = ETj – ETi – d or FF = smallest ES (of succeeding activities) – EF (of current activity) ملاحظة : FF دوما يستخدم للنشاطين السابق واللاحق. ES EF ES EF ES EF ES EF A i j B i j A B LS LF LS LF LS LF LS LF AOA AOA

Total Float (TF) = LF – EF = LS – ES Free Float (FF) = ETj – ETi – d or FF = smallest ES (of succeeding activities) – EF (of current activity) Critical Activity Total Float (TF) Late Finish (LF) Early Finish (EF) Late Start (LS) Early Start (ES) Duration Yes 3 A No 9 6 B 2 7 5 4 C D 14 E

4.3.2 Precedence Diagram Method (PDM): Precedence Diagram Method (PDM) is the CPM scheduling method used for AON networks and it follows the same four steps of the CPM for AOA method. Forward Path Forward path can proceed from one activity to the other; the process is as follow . 3 6 B(3) 6,7,or 9 Early start Early finish 3 3 7 9 14 A(3) C(4) E(5) Name (duration) Late start Late finish 3 9 D(6) Fig. 4.8: Forward Path in PDM Analysis

Backward Path: 3 6 B(3) 6 9 3 3 7 9 14 A(3) C(4) E(5) 3 5 9 9 14 Early start Early finish 3 3 7 9 14 A(3) C(4) E(5) 3 5 9 9 14 Name (duration) 6,5, or 3 Late start Late finish 3 9 D(6) 3 9

Floats Start Completion Start Completion Start Completion Project duration = 24 days Activity A 7 days Activity B 13 days Activity C 4 days CASE 1: All activities are critical: total float and free floats for all activities = 0 Total Float = 5 Free Float = 5 Start Completion Activity D 8 days Activity A 7 days Activity B 13 days Activity C 4 days CASE 2: Activity sequence in which one activity has total and free float Total Float of D = 5 Total Float of E = 5 Free Float of D = 0 Free Float = 5 Start Completion Activity D 5 days Activity E 3 days Activity A 7 days Activity B 13 days Activity C 4 days CASE 3: Activity sequence illustrating total and free float

Floats - 2 TEi TLi TLj TEj Finish Event Start Event Activity duration Total Float Activity duration Free Float Activity duration Independent Float Areas of shared float

Total Float (TF) = LF – EF Float Calculations: Total Float (TF) = LF – EF = LS – ES Free Float (FF) = ETj – ETi – d Activity Duration ES LF LS EF TF Critical Act. A 3 3 Yes 3 B 3 3 9 6 No 6 3 C 4 3 9 5 No 7 2 9 3 Yes D 6 3 9 E 5 9 14 9 Yes 14

PDM Calculations (PDM = Precedence Diagram Method) Example 2/ 4/ 4 0/ 12 20 10 16 6 3 6 E 4 B 3 H 6 12 20 14 8 6 11 3 4 0/ 0/ 0/ 0/ 3 3 8 A 3 C 5 F 6 J 8 Fn 0/ TF/FF 8 12 1/ ES EF 3 10 G 4 Act Dur D 7 1/ 1 10 19 LS LF I 9 TF/FF TFi = LFi - EFi Free Float (FF) = ETj – ETi – d or FF = smallest ES (of succeeding activities) – EF (of current activity)

Precedence Relationships - Lead & Lag FFij Lag time for a finish-to-finish relationship. (The succeeding activity finishes this amount of time after the completion of the preceding activity.) SSij Lead time for a start-to-start relationship. (The preceding activity starts this much earlier than the start of the succeeding activity.) FSij Lag time for a finish-to-finish relationship. (The succeeding activity starts this amount of time after the completion of the preceding activity.) SFij Lead time for a start-to-finish relationship. (The preceding activity starts this much earlier than the completion of the succeeding activity.)

PRECEDENCE LOGIC 1. Preceding Activities.الفعاليات السابقة Which activities must be finished before this activity may begin ? What is the time lag? (finish to start.) Which activities must be started before this activity may begin? What is the lead time (start to start.) Which activities must be finished before this activity may be completed? What is the lag time? (Finish to finish) Which activities must be started before this activity is completed? What is the lead time ? (start to finish.)

Follow: PRECEDENCE LOGIC 2. Succeeding Activities الفعاليات اللاحقة Which activities can begin after the finish of this activity? What is the time lag? (finish to start.) Which activities can begin after the start of this activity? What is the lead time? ( Start to start ) Which activities can be completed after the finish of this activity? What is the lag time? (Finish to finish.) Which activities can finish after the start of this activity? What is the lead time? (Start to finish.) 3. Concurrent Activities. Which activities can be carried out at the same time? (Start to start equals zero, that is, SS = 0 in this case.) R. RUSTOM

Lead/Lag Relationships FF ij Forward Pass j i Dj ES DESC. EF ES DESC. EF Di FS ij SS ij SF ij FF jk Backward Pass k j Dk LS DESC. LF Dj FS jk LS DESC. LF SS jk SF jk

PDM Activity Diagramming Methods Activity No. ES Activity No. EF DESCRIPTION DESCRIPTION Start Side Finish Side Start Side Finish Side LS LF Duration RESP. Duration RESP. METHOD 1 METHOD 2 Activity No. DUR TF ES Activity No. EF DESCRIPTION DESCRIPTION Start Side Finish Side Start Side Finish Side LS LF ES EF Duration RESP. LS LF METHOD 3 METHOD 4

Logical Relationships of PDM 12 20 12 Layout & Excavate Install fuel tanks Layout & Excavate 2 GO 2 GO 2 GO 12 12 12 1 Install exterior Conduit & piping Install exterior Conduit & piping Install exterior Conduit & piping 5 EL 5 EL 5 EL START - TO - START FINISH - TO - FINISH Relationship with Lag 10 10 12 18 Contract Award Layout & Excavate Layout & Excavate Install fuel tanks 2 GO 2 GO 2 GO 2 ME FINISH - TO - START START - TO - FINISH

PDM Calculation Procedure (Assumes no splitting of activity is allowed)

Follow PDM Calculation Procedure

Calculation of Total Float and Free Float

FORWARD PASS ESi + SFij - Dj 15 + 7 -5 EFi + FSij 13 + 2 ESi + SSij 23 + 1 13 15 18 23 28 6 SF7 FS2 F 3 K 5 EFi + FFij - Dj 28 + 2 - 8 B 7 ESi + SSij 21 + 2 EFi + FFij-Dj 13 + 2 -10 FF2, SS1 ESi + SSij 1 +5 = 6 21 FF2 SS2 11 21 31 38 46 SS5 C 10 FS0 G 10 ESi + SSij 16 + 10 N 8 FS0 28 1 11 ESi +SSij 11 + 5 33 ESi+SSij 28+3 EFi + FFij - Dj 31 + 2 - 5 EFij+FSij 37+1 L 5 38 46 A 10 SS5 SS3 SS10, FF2 FS1 FS0 11 21 16 31 31 37 EFi + FFij - Dj 21 + 1 - 7 D 10 H 15 EFi+FSij 23 + 2 M 6 EFi + FFi - Di 11 + 0 - 4 FS2 FF1 EFi + FSij 14 + 3 FS3 16 23 FF0 EFi + FSij 11 +5 7 11 I 7 FS5 11 14 E 4 J 3 FS0 FORWARD PASS

BACKWARD PASS LFj - Sfij + Di 42 - 7 + 3 LSj - FSij 35 - 2 LSj - SSj - Di 38 - 1 + 5 15 18 23 28 6 13 SF7 FS2 F 3 K 5 LFj - FFij 46 - 2 B 7 LSj - SSij + Di 37 - 2 + 10 LFj - FFij 45 - 2 LSj - SSij + Di 26 - 5 + 10 FF2, SS1 33 35 38 37 42 26 FF2 11 21 SS2 21 31 38 46 SS5 C 10 FS0 G 10 LSj - SSij + Di 28 - 10 + 15 N 8 28 33 1 11 LSj - SSij + Di 16 - 5 + 10 LSj - SSij + Di 31 - 3 + 5 11 21 LFi - FFij 33 - 2 L 5 A 10 SF0 35 45 38 46 SS5 SS3 SS10, FF2 FS1 SF0 11 21 31 37 16 31 1 D 10 LFj - FFij 26 - 1 28 33 M 6 11 H 15 LSj - FSij 38 - 1 FS2 15 25 FF1 LSj - FSij 28 - 2 31 37 16 31 FF0 7 11 LSj - FSij 19 - 5 16 23 FS3 E 4 I 7 FS5 LSj - FSij 31 - 3 11 14 11 14 J 3 19 26 SF0 BACKWARD PASS 25 28

TFi = LFi - EFi 20/0 ESj - Sfij - ESi 28 - 7 - 15 ESj - FSij - EFi 15 - 2-13 15 18 ESj - SSij - ESi 38 - 1 - 23 14/14 20/0 F 3 23 28 6 13 SF7 FS2 K 5 EFj - FFij - EFi 46 - 2 - 28 ESj - SSij - ESi 6-5-1 B 7 35 38 EFj - FFij - EFi 31 - 2 - 13 14/0 FF2, SS1 37 42 FF2 21 31 0/0 26 33 SS2 ESj - SSij - ESi 23 - 2 - 21 0/0 ESj - FSij -EFi 21 - 0 - 21 38 46 SS5 aG 10 ESj - FSij - ESj 11 - 0 - 1 0/0 11 21 0/0 N 8 FS0 EFj - FFij - EFi 33 - 2 - 31 28 33 ESj - SSij - ESi 31 - 3 28 1 11 C 10 ESj - SSij - ESi 16 - 5 - 11 35 45 FS0 L 5 A 10 38 46 ESj - SSij - ESi 28 - 10 - 16 SS3 0/0 0/0 11 21 SS5 31 37 FS1 16 31 ESj - FSij - Efi 11 - 0 - 11 28 33 ESj - FSij - EFi 38 - 1 - 37 11 M 6 1 4/1 H 15 SS10, FF2 FS0 11 21 ESj - FFij - EFi 23 - 1 - 21 FS2 D 10 31 37 16 31 FF1 ESj - FSij - EFi 28 - 2 - 23 FF0 3/3 FS3 15 25 ESj - FSij - EFi 16 - 5 - 11 16 23 ESj - FFij -EFi 11 - 0 - 11 ESj - FSij - EFi 31 - 3 - 14 3/0 14/14 I 7 7 FS5 14 11 11 E 4 J 3 19 26 FS0 11 14 25 28 TF/FF TFi = LFi - EFi ESj - FSij - EFi 11 - 0 - 11

4.4 Time-Scaled Diagrams: Time-scaled diagrams are used extensively in the construction industry. Such diagrams enable one to determine immediately which activities are scheduled to proceed at any point in time . to monitor field progress. it can be used to determine resources need. The time scale used in time-scaled diagrams can be either the calendar dates or the working periods (ordinary dates), or using both at the same time. Its disadvantage is that it needs a great effort to be modified or updated. Also, it can not be used to represent overlapping activities. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 B Time-scaled diagram 3 3 A C E 3 4 2 5 D 6

The TF for activity A equals the smallest of the sum of the floats along all paths from the end of activity A to the end of the project. The float on path ABE = 3, path ACE = 2 and path ADE = 0, then the TF of activity A = 0. The calculations are shown in Table 4.2. Table 4.2 Time-scaled diagram calculations

4.5 Schedule Presentation: After the AOA and AON calculations are made, it is important to present their results in a format that is clear and understandable to all the parties involved in the project. The simplest form is the Bar chart or Gantt chart, named after the person who first used it. A bar chart is a time versus activity chart in which activities are plotted using their early or late times. a) Early bar chat b) Late bar chart

The bar chart representation: It shows various details. Float times of activities, critical activities can be shown in a different color, or bold borders, as shown in Figure 4.12. The bar chart can also be used for accumulating total daily resources and / or costs, as shown at the bottom part of Figure 6.13. In this figure, the numbers on each activity represent the number of labors needed. Figure 4.13: Using bar chart to accumulate resources

4.6 Criticisms to Network Techniques: 1- Assume all required resources are available: The CPM calculations do not incorporate resources into their formulation. Also, as they deal with activity durations only, it can result in large resource fluctuations. Dealing with limited resources and resource leveling, therefore, has to be done separately after the analysis. 2- Ignore project deadline: The formulations of CPM and PDM methods do not incorporateغير مندمجة a deadline duration to constrain project duration. 3- Ignore project costs: Since CPM and PDM methods deal mainly with activities durations, they do not deal with any aspects related to minimize project cost. 4- Use deterministic durations: The basic assumption in CPM and PDM formulations is that activity durations are deterministic. In reality, however, activity durations take certain probability distribution that reflect the effect of project conditions on resource productivity and the level of uncertainty involved in the project.

4.7 Solved Examples Example 3.1 For the project data in Table 4.3, answer the following questions: a) Draw an AOA network of the project? b) Perform forward path and backward path calculations c) What is the effect of delaying activity D by 3 days?

c) Total float of activity D = LF – ES – d = 11 – 8 – 1 = 2. Solution: a, b 8 8 8,or10 3 2,or 8 E 14,or12 B 6 2 2 14 14 16 16 6 G 1 A 2 5 6 2 2 D 1 C F 3 3 4 9,or 5 9 11 c) Total float of activity D = LF – ES – d = 11 – 8 – 1 = 2.

Example 3.2 Perform PDM calculations for the small project below and determine activity times. Durations are shown on the activities.

Solution: 7 9 I(2) 1 5 5 6 6 7 B(4) D(1) G(1) 1 5 5 6 6 7 12or7 L(2) 7 14 B(4) D(1) G(1) 9or9or14 1 5 5 6 6 7 14 16 12or7 L(2) 7 14 1 14 16 J(7) A(1) 7 14 1 1or6 1 2 2 4 4 5 C(1) E(2) H(1) 6 7 7 9 9 10 7or8 5or4 5 9 2 4 K(4) F(2) 10 14 8 10

Example 3.3 For the activities listed in the table below, draw the time-scaled diagram and mark the critical path. Determine the completion time for the project. Tabulate activities times and floats.

Solution:

Example 3.4 Perform PDM calculations for the small AoN network shown here. Pay special attention to the different relationships and the lag times shown on them. SS2 2 5 B(3) 4 7 5 or 7 or 2=9-2-5 3 3 7 7 12 A(3) Solution: C(4) E(5) 3 3 7 7 12 4 or 3 or 5=4-2+3 3 9 FF2 D(6) 4 10 12-2=10 8

Exercise 4

Exercise 4 (Cont.)

Exercise 4 (Cont.)

Exercise 4 (Cont.)

Exercise 4 (Cont.)

Exercise 4 (Cont.)

Exercise 4 (Cont.)