1
Network Diagramand Critical Path
COSC 621Advanced Construction Project
Scheduling & Management
Construction Planning
A general term that sets a clear road map that should be followed to reach a destination.Plans at several levels in construction projects
Corporate strategic plansPretender plansPrecontract plansShort-term construction plansLong-term construction plans
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Planning: A ChallengePlanning is the most crucial, knowledge-intensive-ill-structured, and challenging phase in the project development cycle.Planning is the process of representing the project scope by its identifiable components.
Breakdown of the project into definable, measurable, and identifiable work tasksThe logical interdependence among them.What is to be done?How to dot it?Who does it?
Planning: A ChallengeSystematic and structured planning techniques are important for:
Minimizing the potential to overlook somethingSharing of team-work ideasHaving a clear definition of project scope and desired level of detailBuilding confidence and commitment into team workersEffectively communicating the plan to site personnel
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Logical Relationships
What activities must be finished before the current one can start?What activities may be constructed concurrently with the current one?What activities must follow the current one?
Logical Relationships
Activity Description DependsUpon
ABCDEFGHJKLM
Site clearingRemoval of treesExcavationGradingExcavation for utility trenchesPlacing formwork and reinforcement for concreteInstalling sewer linesPouring concreteObtain formwork and reinforcing steelObtain sewer linesObtain concreteSteelworker availability
--A
A,B,CA,B,C
B,C,J,MB,C,D,E,KD,E,F,G,L
----
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Logical RelationshipsA B C
Redundant
Relationship
Activity Depends UponImmediatelyPrecedingActivity (IPA)
ABC
---AA,B
---AB
Logical Relationships
Activity Description IPA
ABCDEFGHJKLM
Site clearingRemoval of treesExcavationGradingExcavation for utility trenchesPlacing formwork and reinforcement for concreteInstalling sewer linesPouring concreteObtain formwork and reinforcing steelObtain sewer linesObtain concreteSteelworker availability
--A
A,B,CA,B,C
B,C,J,MB,C,D,E,KD,E,F,G,L
----
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Drawing Project Network
Activity Description IPA
STABCDEFGHJKLMFN
Start ActivitySite clearingRemoval of treesExcavationGradingExcavation for utility trenchesPlacing formwork and reinforcement for concreteInstalling sewer linesPouring concreteObtain formwork and reinforcing steelObtain sewer linesObtain concreteSteelworker availabilityFinish Activity
--STSTA
B,CB,C
B,C,J,MD,E,KF,G,L
STSTSTSTH
Drawing Project Network:Activity On Arrow (AOA)
Activity on Arrow (AOA) Method of Network Drawing
The arrow represents activities while the nodes represent the start and the end of an activity.The length of the arrow has no significanceEach activity has a definite beginning and end represented by nodes (commonly called events)Each activity mush have a unique i-j reference numbers
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Drawing Project Network:Activity On Arrow (AOA)
5 10Activity A
Event i Event j
j>i 5 10Activity A
5 10A
15B
5
15
A
20B10
C
Drawing Project Network:Activity On Arrow (AOA)
5
15
A 20
B10
C
25D
5 10A
15B
20C
7
Drawing Project Network:Activity On Arrow (AOA)
5
20
A25
B10
C
30D
15
Dummy
Drawing Project Network:Activity On Arrow (AOA)
5
A
10
B
5A
15
B
10
Dummy
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Drawing Project Network:Activity On Node (AON)
Activity on Node (AON) Method of Network Drawing
Precedence diagram methodAn activity is represented by a name and a corresponding number enclosed in a symbol
Drawing Project Network:Activity On Node (AON)
10A
Activity number
Activity name
10A
20B
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Drawing Project Network:Activity On Node (AON)
10A
30C
20B
40D
10A
20B
30C
40D
Drawing Project Network:Activity On Node (AON)
ST(1)
J(2)
A(2)
B(2)
K(2)
M(2)
C(2)
D(4)
L(2)
E(4)
F(4)
G(5)
H(6)
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Drawing Project Network:Activity On Node (AON)
Activity Sequence Step (SS)IPA
STABCDEFGHJKLMFN
SS(ST) = 12 = 1 + SS(ST)2 = 1 + SS(ST)3 = 1 + SS(A)4 = 1 + Highest of [SS(B), SS(C)]4 = 1 + Highest of [SS(B), SS(C)]4 = 1 + Highest of [SS(B), SS(C), SS(J), SS(M)]5 = 1 + Highest of [SS(D), SS(E), SS(K)]4 = 1 + Highest of [SS(F), SS(G), SS(L)]2 = 1 + SS(ST)2 = 1 + SS(ST)2 = 1 + SS(ST)2 = 1 + SS(ST)7 = 1 + SS(H)
--STSTA
B,CB,C
B,C,J,MD,E,KF,G,L
STSTSTSTH
Drawing Project Network:Activity On Node (AON)
5ST
15J
20A
25B
30K
10M
40C
45D
35L
50E
55F
60G
65H
70FN
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Critical-Path Analysis
COSC 621Advanced Construction Project
Scheduling & Management
Introduction
Perform CPM and PDM analyses for AOA and AON networksCalculate the early / late times that an activity can start / finish.Determine the total project duration, activity floats, and the path of critical activities.Represent the schedule using bar charts (Gantt charts)
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IntroductionWe have known
The picture of the inter-relationships within a project.The time and cost of individual activities based on our estimation of the resources and methods of construction to be used.
However,How long the total project duration would be?When is the earliest or latest times at which activities start and finish?What are the critical activates so that special care is taken to make sure they are not delayed?
Meaning of Construction Scheduling
For contractorsWhen and how much labor is needed?
For vendorsWhen they need to deliver materials?
For subcontractorsWhen they can do their work?
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Network Scheduling:Critical Path Method (CPM)
A forward pass to determine activities early-start times.A backward pass to determine activities late-finish times.Float calculations.Identifying critical activities.
Network Scheduling:Critical Path Method (CPM)
Forward pass in AOA networks
1 3
5
7
9 11A
D
C
d1B
d2
E0 3
6
9
9
14
ProjectStart=0
ES+d=EF0+3=3
d=3
3
64 5
3+3=6
9+5=14
6+0=6 or3+4=7 or9+0=9
3+6=9
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Network Scheduling:Critical Path Method (CPM)
Backward pass in AOA Networks
1 3
5
7
9 11A
D
C
d1B
d2
E0 3
6
9
9
14
ProjectStart=0
9-3=6 or9-4=5 or9-6=3
3
3
64 d=5
9-0=9
ProjectLate finish
14-5=9LF-d=LS
0 3
9
9
9
14
9-0=9
Network Scheduling:Critical Path Method (CPM)
ES EF=ES+d Total Float
ES Total Float LS=LF-d
LF
LF
i jName
Duration=d
ES LF
Total time available for the activity = LF - ES
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Network Scheduling:Critical Path Method (CPM)
FloatNumber of days that an activity, event, or lag can be delayed or extended without impacting the overall completion of the project
Starting FloatNumber of days that the start of an activity can be delayed without impacting the completion of the project or the late finish of the specific activityStarting Float = Late Start – Early Start
Finish FloatNumber of days that the completion of an activity can be postponed without impacting the completion of the project.Finish Float = Late Finish – Early Finish
Network Scheduling:Critical Path Method (CPM)
Task Float or Total FloatNumber of days that the duration of a specific activity can be increased without impacting the project completion.Task Float = Late Finish – Early Start - Duration
Free FloatNumber of days that an activity can be delayed without taking float away from any other activity.Free Float = ES(Succeeding activity) – EF(Activity in question)
Relationship FloatRelationship Float(Start-to-Start) = LS(Successor Node) – ES(Predecessor Node)
– LagRelationship Float(Finish-to-Finish) = LS(Successor Node) – ES(Predecessor Node)
– LagRelationship Float(Finish-to-Start) = LS(Successor Node) – ES(Predecessor Node)
– Lag
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Network Scheduling:Critical Path Method (CPM)
Yes01491495E
Yes093936D
No275934C
No366933B
Yes030303A
CriticalActivity
Total FloatTF=LF-ES-d
Early FinishEF=ES+d
Late StartLS=LF-d
Late Finish (LF)
Early Start(ES)
Duration(d)
Activity
FloatCalculations
Calculations of OtherActivity Times
Results of ForwardAnd Backward Pass
Network Scheduling:Precedence Diagram Method (PDM)
A (3)
30
B (3)
63
C (4)
73
D (6)
93
E (5)
149
6, 7, or 9
Name (duration)
Early finishEarly start
Forward Pass
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Network Scheduling:Precedence Diagram Method (PDM)
30
A (3)
30
96
B (3)
63
95
C (4)
73
93
D (6)
93
149
E (5)
149
3, 5, or 6
Late finishLate start
Name (duration)
Early finishEarly start
Backward Pass
Primavera Project Planner
COSC 621Advanced Construction Project
Scheduling & Management
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Primavera Project PlannerCreating a New ProjectCalendar Setup
Standard Daily InformationHolidays ListSelecting Nonwork PeriodAdd 2nd Calendar
Activity CodesAllow the project planner to track the project by specific geographic areas as well as generate information about the entire project.Useful for assigning individual superintendents to specific activities.Total of 64 characters.
Project CodesSet of fixed fields that allow the user to enter project specific descriptive information.
Primavera Project PlannerActivity Input
Activity Incrementing (Tool > Options > Activity Inserting…)Activity Types
Task: Schedules activities according to the base calendar assigned to it.Independent: Works according to its own resource calendar.Meeting: Schedules a meeting activity when all resources attached to the
activity are available.Start Milestone: Marks the start of a significant event in the project.Finish Milestone: Marks the end of a significant event in the project.Start Flag: Marks the start of a string of activities.Finish Flag: Marks the end of a string of activities.Hammock: An activity that spans a group of activities.WBS: Rolls up or summarizes activities that have common prefixes.
Importing Activity DataGenerating a Template: Tool > Project Utilities > Exports…
Relationship InputFormat > Row Height…Calculating the Schedule
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Primavera Project PlannerCalculating the Schedule
Schedule durations: Contiguous or InterruptibleCalculate total float as: Most critical, Start float, or Finish Float
Changing the Time ScaleReorganizing the ScheduleSaving a ProjectOpening an Existing ProjectBacking Up ProjectsRestoring a ProjectGenerating Reports
Early Start ReportCritical Activity List ReportResponsibility Schedule Report
Graphical ReportsBar Chart ScheduleTimescaled Logic Diagrams
Primavera Project PlannerResource Loading
Defining ResourcesDefining Cost AccountsLoading Resources on the Individual ActivitiesProducing Resource Loading ReportsGraphic Resource Output
Cost Loading and Cash FlowLoading Cost Data on the Individual ActivitiesCash Flow
Schedule of ValuesProgress PaymentsProject Cash Inflows PlanCost Loading ReportProject Cost Plan
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Primavera Project PlannerProgress Planning and Control
Developing the Progress PlanDetermining Actual Project ProgressCreating Planned Progress Curves
Project Analysis and ForecastingProject CostsAnalysis of Labor Operations ReportLabor PerformanceProject ProgressMaterial and Subcontract Costs
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
Primavera Project Planner
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Primavera Project Planner
A(4)
B(6)
D(8) E(4)
F(10)
C(2) J(6)
K(10)
H(8) I(6)Start
EndG(16)
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