Project Scheduling Class 4 Network formation Network Analysis

Project Scheduling Class 4 • Network formation • Network Analysis • Bar chart • Resources Free Powerpoint Templates Page 1

Network Formation • A project network is a tool used for planning, scheduling, and monitoring project progress. • Network is a graphical representation of the project or part of it, showing all of the activities and their relationships. • Network is developed from the information collected for the WBS. Free Powerpoint Templates Page 2

Definition • Activity: is an element of the project that requires time, may or may not require resources. • Path: is a sequence of connected, dependent activities • Critical Path: is the longest path(s) through the network, if an activity on the path is delayed, the project is delayed the same amount of time. • Event: This term is used to represent a point in time when an activity is started or completed. It does not consume time. • Predecessor: activity must be completed before • Successor: activity must immediately follow it Free Powerpoint Templates Page 3

1 3 5 START 2 4 Free Powerpoint Templates Page 4

Basic rules in developing project network 1. Networks flow typically from left to right. 2. An activity cannot begin until all preceding connected activities have been completed. 3. Arrows on networks indicate precedence and flow. Arrows can cross over each other. 4. Each activity should have a unique identification number. 13 Free Powerpoint Templates 15 Page 5

5. An activity identification number must be larger than that of any activities that precede it. 2 3 6 1 8 4 5 7 2 4 6 1 8 3 5 7 Free Powerpoint Templates Page 6

6. Looping is not allowed. 7. Condition statements are not allowed. 8. When there are multiple starts, a common start node can be used to indicate a clear project beginning on the network. Dummy A Y Dummy B Z Free Powerpoint Templates Page 7

Project Networks There are 2 types: 1. Activity-on-Arrow (AOA) / Arrow Diagram 2. Activity-on-Node (AON) / Precedence Diagram Free Powerpoint Templates Page 8

Arrow Diagrams • The arrow diagram represents an individual project activity that requires time. • Arrow diagrams were the first form of network diagram to be developed. • The length and slope of the arrow diagram have no significance. Free Powerpoint Templates Page 9

Activities and Events Activities are represented by arrows starting and terminating at nodes or events. START FINISH ACTIVITY Free Powerpoint Templates Page 10

Predecessor-Successor Relationships Time relationships between activities is indicated by connecting activities through events. ACTIVITY 1 ACTIVITY 2 ACTIVITY 1 ACTIVITY 3 ACTIVITY 2 (2 sources) Free Powerpoint Templates Page 11

Concurrence Relationships Some activities can be performed at the same time, referred to as concurrent activities. ACTIVITY 1 ACTIVITY 2 Free Powerpoint Templates Page 12

Dummy Activities Sometimes the logic of the operation cannot be adequately described using only real activities and dummy activities need to be created. ACTIVITY 1 ACTIVITY 3 ACTIVITY 2 ACTIVITY 4 Free Powerpoint Templates Page 13

ACTIVITY 1 • Dummy activities have no duration, cost nothing, and use no resources. • Dummy activities are normally drawn using dotted lines. ACTIVITY 2 Free Powerpoint Templates Page 14

Artificial Activity An artificial activity is used to create a delay. It has a duration, but no cost or resources. Circuits As such circuits or loops are not possible, should avoid. Free Powerpoint Templates Page 15

Aggregated Activity Occasionally it is conventional to group a collection of activities and replace this group with a single activity. F B A C D E H G Free Powerpoint Templates Page 16

Example – Arrow diagram Activity Predecessor A - B - C A D B E B F C, D G E Free Powerpoint Templates Page 17

Case#1 Arrow diagram Activity Preceding Activity Times A - 5 B A 15 C A 10 D A 5 E B, C 15 F B, C, D 10 G F 170 H E, G 35 Free Powerpoint Templates Page 18

Case#2 Arrow diagram Activity Preceding Activity A - B - C A, B D A, B E A, B F C, D G E H F I F, G Free Powerpoint Templates Page 19

Case#3 Bridge building – Arrow diagram Activity Code Operation Dependence Duration ENA Earthworks, north side - 5 ESA Earthworks, south side ENA 4 CONN Construction, north side ENA 14 CONS Construction, south side ESA, CONN 12 COMN Compaction, north side CONN 2 COMS Compaction, south side CONS, COMN 2 RNB Road, north of bridge COMN 2 RSB Road, south of bridge RNB, COMS 2 PB Prefabrication bridge deck - 18 TD Transport deck to site PB 2 EB Erect bridge deck TD, CONN, CONS, COMN 3 LBS Lay bridge surface EB, RNB, RSB 2 ICB Install crash barriers EB 1 L Landscape RNB, RSB 1 Free Powerpoint Templates Page 20

Precedence Diagrams • In this diagram the nodes represent the activities and the arrows give the precedence relationships between them. • Widely availability if personal computers and graphics programs Free Powerpoint Templates Page 21

AOA to AON A B D E C Free Powerpoint Templates Page 22

A B D C A B C D Free Powerpoint Templates Page 23

C A B D Free Powerpoint Templates Page 24

Example – Precedence diagram Activity Predecessor A - B - C A D B E B F C, D G E Free Powerpoint Templates Page 25

Case#4 Precedence diagram Activity Preceding Activity Times A - 5 B A 15 C A 10 D A 5 E B, C 15 F B, C, D 10 G F 170 H E, G 35 Free Powerpoint Templates Page 26

Case#5 Precedence diagram Activity Preceding Activity A - B - C A, B D A, B E A, B F C, D G E H F I F, G Free Powerpoint Templates Page 27

Case#6 Bridge building – Precedence diagram Activity Code Operation Dependence Duration ENA Earthworks, north side - 5 ESA Earthworks, south side ENA 4 CONN Construction, north side ENA 14 CONS Construction, south side ESA, CONN 12 COMN Compaction, north side CONN 2 COMS Compaction, south side CONS, COMN 2 RNB Road, north of bridge COMN 2 RSB Road, south of bridge RNB, COMS 2 PB Prefabrication bridge deck - 18 TD Transport deck to site PB 2 EB Erect bridge deck TD, CONN, CONS, COMN 3 LBS Lay bridge surface EB, RNB, RSB 2 ICB Install crash barriers EB 1 L Landscape RNB, RSB 1 Free Powerpoint Templates Page 28

Comparison of AON and AOA method Advantages: 1. Path tracing is simplified by activity/event numbering scheme 2. AOA is easier to draw if dependencies are intense 3. Key events or milestones can easily be flagged Disadvantages: 1. Use of dummy activities increases data requirements 2. Emphasis on events can distract from activities Free Powerpoint Templates Page 29

AON method Advantages: 1. No dummy activities are used 2. Events are not used 3. AON is easy to draw if dependencies are not intense 4. Activity emphasis is easily understand by first-level managers Disadvantages: 1. Path tracing by activity number is difficult 2. Network drawing and understanding are more difficult when dependencies are numerous Free Powerpoint Templates Page 30

Network Analysis The Critical Path is the minimum time that it takes to complete a project is the longest sequence of activities in the network • There maybe more than one critical path through a network; but one is better • The activities that lie along critical path are called critical activities • If a critical activity is delayed then the whole project is delayed Free Powerpoint Templates Page 31

15 15 20 10 30 25 5 10 How long does it take to finish this project? Where is critical path? Free Powerpoint Templates Page 32

Case#7 Critical Path Activity Preceding Activity Times A - 5 B A 15 C A 10 D A 5 E B, C 15 F B, C, D 10 G F 170 H E, G 35 Free Powerpoint Templates Page 33

Case#8 Critical Path A city requests federal funding for a par-and-ride project. Network plan is to be submit. Make the critical path. ID Description Predecessor Time A Survey - 5 B Soils report A 20 C Traffic design A 30 D Lot layout A 5 E Approve design B, C, D 80 F Illumination E 15 G Drainage E 30 H Landscape E 25 I Signing E 20 J Bid proposal F, G, H, I 10 Free Powerpoint Templates Page 34

Analysing Network EST – earliest start time LST – latest start time EFT – earliest finish time LFT – latest finish time TF –Total float FF – Free float IF – Interfering float Free Powerpoint Templates Page 35

• Earliest times: are the earliest times that an activity can start and finish given that all preceding activities as soon as possible • Latest times: are the latest that an act can start and finish and still allow time for succeeding activities to be completed without holding up the project • TF = LST-EST = LFT – EFT is the amount of time that an act can be delayed without effecting the overall duration Critical path; TF = 0 Free Powerpoint Templates Page 36

• FF: is the amount of time that an activity can be delayed without affecting any other activity 10 20 20 • IF = TF –FF will affect succeeding activities but not the total project duration Free Powerpoint Templates Page 37

EST EFT LST LFT FF TF 10 10 15 20 10 Free Powerpoint Templates Page 38

EST EFT LST LFT FF TF 15 20 10 20 20 30 Free Powerpoint Templates Page 39

Bar charts • Also known as a Gantt bar chart • Gives a pictorial representation of when the activities begin, when they end, how long they take and how much float they have Free Powerpoint Templates Page 40

Overlapping relationships Preceding Activity Following Activity Start to Start S/S Start to Finish S/F Finish to Start Finish to Finish F/S F/F • Length of the arrows represents the lead times (LT) • Overlapping makes project faster Free Powerpoint Templates Page 41

RESOURCES • • • Resources are things that are needed to carry out project activities Main resources: Man – workers, Engineers, Proj. Man. Machine – pumps, cranes Materials – steel, pipe, bolts&nuts Why manage resources: 1. Resource Constrained Scheduling 2. Resource Leveling Free Powerpoint Templates Page 42

1. Resource Constrained Scheduling • Limited resources • Sometimes resources are restricted; some activities need to be delayed because of not enough resources • Where schedule is constrained by the available resources and may have to increase the duration of the project Free Powerpoint Templates Page 43

Reasons for resource limited: • Space constraints • Limited facilities • Safety requirements limit • Limited amount of equipment to work on Solutions: • Working overtime • Working shifts • Training, education, automation = increase productivity • Learning curve = repetitive • Hire sub-contractors • Reduce scope of work Free Powerpoint Templates Page 44

Resources Resource limited Extend Project duration Time Free Powerpoint Templates Page 45

2. Resource Leveling • Hiring & Firing • Resources cost money even though no work is being done • A uniform resource usage will prevent resources being idle and to minimize hiring and firings • Safety, learning curve, skilled workers, happy, lower price, more work, more profit • Duration of project is limited • No one approach is accepted as the best Free Powerpoint Templates Page 46

Resources Time limited Time • Rearrange activities within project duration • Moving activities around in order to smooth the resource profile Free Powerpoint Templates Page 47

B 3 days, 2 men 5 days, 3 men A D 5 days, 2 men C 4 days, 4 men Free Powerpoint Templates Page 48

Activity Preceding Activity Times Resources A - 6 3 B - 4 3 C - 3 2 D A 2 4 E A, B 3 1 F B, C 5 1 G D, C 3 2 H E, F 2 2 I C, H 4 2 J G 3 3 Free Powerpoint Templates Page 49

Example a) Draw an arrow diagram b) Analyze network giving EST, EFT, LST, LFT, FF and TF c) Construct a resource profile d) Assuming that you only have 6 units of resource; reschedule the activities to fit the resource limitations Free Powerpoint Templates Page 50

Activity Follows Duration (days) Resource A - 8 2 B - 10 4 C - 12 1 D A 20 3 E A 5 4 F C 16 2 G C 13 0 H D 14 1 I B, D, E, F 8 1 J B, E, D, F, G 16 0 Free Powerpoint Templates Page 51