MODULE -3 NETWORK ANALYSIS AND EXECUTION

PLAN

PROJECT CONSTRUCTION ALTERNATIVES

FACTORS IN THE CHOICE OF PROJECT CONSTRUCTION ALTERNATIVES

CONCEPT OF NETWORK

Conceptually, it can be said that a network diagram is a graphical presentation of all the activities of a project, arranged in a proper sequence and with clearly established interdependencies .The network diagram provides a full picture of the project . The diagram can be presented as:

PERT

There are two basic network techniques: PERT and CPM. PERT is the, There are two basic network techniques: PERT and CPM. PERT is the, acronym for acronym for Program Evaluation Review Technique Program Evaluation Review Technique has a ‘probabilistic’ has a ‘probabilistic’ orientation. CPM, an acronym for orientation. CPM, an acronym for Critical Path MethodCritical Path Method has a deterministic has a deterministic orientationorientation

The common characteristics of the The common characteristics of the projects which make them amenable projects which make them amenable to analysis by PERT or CPM are :to analysis by PERT or CPM are :

1.1. The project can be broken down into a well-defined set of jobs or The project can be broken down into a well-defined set of jobs or activities.activities.

2.2. The activities must be performed in a certain sequence which is The activities must be performed in a certain sequence which is technologically ordered.technologically ordered.

3.3. Within a defined sequence, the activities may be started and Within a defined sequence, the activities may be started and stopped in an independent manner.stopped in an independent manner.

DEVELOPMENT OF PROJECT NETWORK

Basic to PERT as well as CPM is the network diagram. The network diagram, also referred to as the project graph, shows the activities and events of the project and their logical relationships. A simplified net work diagram for a dinner project is shown below

1

3

2

4

Receive guests

Take dinner

Prepare

dinner

Send

invit

ation

s

Network Diagram for a Dinner Project

Development of Project Network

Basic to PERT as well as CPM is the network diagram. The network diagram, also referred to as the project graph, shows the activities and events of the project and their logical relationships. A simplified net work diagram for a dinner project is shown below

1

3

2

4

Receive guests

Take dinnerPrepare dinner

Send

invit

ation

s

Network Diagram for a Dinner Project

The network diagram is constructed in terms of activities and events.

1.An activity is a definite task, job, or function to be performed in a project. For example, ‘prepare dinner’ is an activity. An activity is represented by an arrow. The head of the arrow marks the completion of the activity and the tail of the arrow marks its beginning. (The length and ‘compass’ direction of the arrow have no significance).

2.An event is a specific point in time indicating the beginning or end of one or more activities. It represents a milestone and does not consume time or resources. For example, event 2 marks completion of the activity ‘send invitation’.

Development of Project Network

Basic to PERT as well as CPM is the network diagram. The network diagram, also referred to as the project graph, shows the activities and events of the project and their logical relationships. A simplified net work diagram for a dinner project is shown below

1

3

2

4

Receive guests Act-3

Take dinner Act-4

Prepare dinner Act-2

Send

invit

ation

s Act-

1

Network Diagram for a Dinner Project

Arrow head End of activity

Beginning of activity

Development of Project Network

Basic to PERT as well as CPM is the network diagram. The network diagram, also referred to as the project graph, shows the activities and events of the project and their logical relationships. A simplified net work diagram for a dinner project is shown below

1

3

2

4

Receive guests Act-3

Take dinner Act-4Prepare dinner

Act-2

Send

invit

ation

s Act-

1

Network Diagram for a Dinner Project

Arrow head End of activity

Beginning of activity

Steps for building net work

Rules for Network Construction

1.1. Each activity must have a preceding and a Each activity must have a preceding and a succeeding event. There are 4 activities . Each succeeding event. There are 4 activities . Each activity has preceding and succeeding eventsactivity has preceding and succeeding events

2.2. Each event should have a distinct number.Each event should have a distinct number.

3.3. There should be no loops in the project network.There should be no loops in the project network.

4.4. No more than one activity can have the same preceding No more than one activity can have the same preceding and succeeding events.and succeeding events.

Send invitations 1-2

Receive guests Act- 2-3 Take dinner Act-3-4

Prepare dinner 1-3

1

23Loop

1 2

A building project consists of the following activities:A.Lay foundationB.Erect frame workC.Install mill workD.Install wiringE.Install plumbingF.Plaster wallsG.Install sidingsH.Decorate the interiorI.Finish the exteriorInter relation ship among these activities are:

1.A should precede B2.B should precede C,D,E,F and G3.C,D,E,F should precede H4.G should precede I

EXERCISE

1 2 3

4

5

6

7

8

Lay Foundation

Erect Foundation

DecorateInterior

Install

Siding

Plaster Walls

Install

Plumbing

Install Wiring

Install Millwork

8

Finish

ex

terio

r

TIM

E E

STIM

ATIO

NOnce the logic and detail of the network have been established, time estimates must be assigned to each activity. Generally, three time values are obtained for each activity:

1. Optimistic time (to) The optimistic time, to, is the time required if no hurdles or complications arise.

2. Most likely time (tm)

The most likely time, tm, is the time in which the activity is most likely to be completed. This estimate takes into consideration normal circumstances, making allowance for some unforeseen delays

3. Pessimistic time (tp)

The pessimistic time, tp, is the time required if unusual complications and / or unforeseen difficulties arise.

OB

TAIN

ING

TIM

E E

STIM

ATE

STime estimates should be obtained by the PERT planner from persons who are responsible for estimation. The following points should be borne in mind while obtaining time estimates:

Average Time

Once the three estimates for each activity are obtained, the expected value of activity duration is calculated. The expected value, te, is usually obtained by the formula

to + 4 tm + tp

6

Where te = weighted arithmetic average time

to = optimistic time

tm = most likely time

tp = pessimistic time

te =

Activity Optte

Most Likely tm

Pessimistictp

Average T0t0 +4tm+tp/6

1-2 9 12 21 9+4*12+21/6=13

1-3 6 12 18 12

2-4 1 1.5 5 2

3-4 4 8.5 10 8

2-5 10 14 24 15

4-5 1 2 3 2

1

43

2

5

13

12 8 2

2

15

0 0

13

28 28

13

20 2612 18

1

2

34

5

2

13

8

12

15

2

Critical and Slack Paths

0 0

13

28 28

13

20 2612 18

1

2

34

5

Critical Path Critical Path

2

13

8

12

15

2

Critical Path = No Slack , No cushion= 1-2-5

Activity Floats

Event Slacks

The slack for an event is the difference between its LOT and EOT. The slacks for various events of our illustrative project are shown below.

Event LOTIn Weeks

EOTIn Weeks

SlackLOT-EOTIn Weeks

5 28 28 0

4 26 20 6

3 18 12 6

2 13 13 0

1 00 00 0

0 0

13

28 28

13

20 2612 18

1

2

34

5

2

13

8

12

15

2

Critical and Slack Paths

0 0

13

28 28

13

20 2612 18

1

2

34

5

Critical Path Critical Path

2

13

8

12

15

2

Critical Path = No Slack , No cushion= 1-2-5

Activity Floats

The slack for an event is the difference between its LOT and EOT. The slacks for various events of our illustrative project are shown below.

Event LOTIn Weeks

EOTIn Weeks

SlackLOT-EOTIn Weeks

5 28 28 0

4 26 20 6

3 18 12 6

2 13 13 0

1 00 00 0

Event Slacks

PURPOSE OF NETWORK ANALYSIS

BASIC DECISIONSTwo basic decisions are important before the network techniques are deployed:

MULTI-LEVEL SCHEDULINGDifferent levels of management need different degrees of details in the schedule plan and network diagram.When schedules are prepared at multiple levels , it is known as multi level scheduling. Three to four level schedules can be prepared depending upon the requirements:

MULTI-PROJECT SCHEDULING

A firm, handling more than one project simultaneously, may require multi-project planning and resource allocation.

In multi-project scheduling, all projects collectively are treated as a single project for the breakdown of work packages, their sequencing

and resource allocation. Activities of one project may have predecessor activities and/or successor activities

in other projects. It becomes imperative for multi-project scheduling to follow multilevel scheduling also and plan for a greater degree of

communication, reporting and coordination.

CATS AND RATS

The term CATS stands for Critical Activity Time Schedule and the term RATS for Realistic Activity Time Schedule.

CATS can be used to provide stringent time standards for project execution and can be useful for setting targets for project teams, machine fabricators and other project contractors for the completion time.

RATS provide a more realistic time planning; therefore, it can be used for negotiations with funding agencies, who would expect timely attainment of major milestones in the project construction before they would release additional installment of loan.

STEPS INVOLVED IN NETWORK TECHNIQUES AND ANALYSIS

APPLICATION OF NETWORK TECHNIQUES

RESOURCE PLANNING

BUDGETING

PROJECT PLANNING SOFTWAREProject-management software packages offer facilities to accept project network data, perform resource analysis, scheduling and cost analysis, along with generating reports for monitoring of a project. Popular project management packages are MS Project, Intellisys Project, Open Mind, Project Kick Start, INSTAPLAN, PRISM andmany others.

Fig: Ranking of Project Management Software ,2008

DETAILED PROJECT REPORT (DPR)

CONTRACTINGA substantial portion of project is typically executed through contracts

assigned to the external contractors.

Types of Contracts

PROJECT ORGANIZATION

A firm would require the right type of organizational structure for the construction of a project . The firm would have that organizational structure, which would suit the needs of routine operations. Project structure is superimposed on the existing organizational structure. The overlapping of the two structures does create problems.

The firm has to answer the following questions while making the choice of project organization:

a) How much independence should be given to the project team?

b) Where should a project organization fit in the total organization?

c) How should people be assigned to the project?

d) What directive/authority should managers have (i.e., degree of empowerment)?

TYPES OF ORGANIZATIONS

PROJECT SUB-TEAMS AND EMPOWERMENT

Each activity is planned, its relationship with other activities, if any are determined, resources for performing each activity are determined and then each activity is assigned to a project sub-team. Sub-teams have to be formed as per the expertise needed and activities are assigned to each sub-team. Their powers and responsibilities have to be determined based on the criticality of the activities assigned to them.