06 Network Diagram and Critical Path

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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?


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

----

4

Logical RelationshipsA B C

Redundant

Relationship

Activity Depends UponImmediatelyPrecedingActivity (IPA)

ABC

---AA,B

---AB


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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5 10Activity A

Event i Event j

j>i 5 10Activity A

5 10A

15B

5

15

A

20B10

C


5

15

A 20

B10

C

25D

5 10A

15B

20C

7


5

20

A25

B10

C

30D

15

Dummy


5

A

10

B

5A

15

B

10

Dummy

8

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


10A

Activity number

Activity name

10A

20B

9


10A

30C

20B

40D

10A

20B

30C

40D


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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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


5ST

15J

20A

25B

30K

10M

40C

45D

35L

50E

55F

60G

65H

70FN

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Critical-Path Analysis



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.


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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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


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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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


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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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



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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


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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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06 Network Diagram and Critical Path

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