Network Techniques: Bar Chart, Mile stone chart,

work break down

Structure and preparation of networks.

Network techniques like PERT and CPM.

In construction Management, Project Monitoring and resource

allocations through network techniques.

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BY MODASSAR ANSARI

3RD Year

Department of civil Engineering

SUBJECT- Construction Technology And Management

SUBJECT CODE-NCE 603

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Gives Pictorial Representation of Activities.

Activities begin at EST and show their EFT, FF, TF, Durations, etc.

Arrows at the relative ends to show dependency.

Status Line Concept

Unable to show complete interdependency between Activities.

Time-scaled Network Diagrams show complete interdependency between Activities.

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A work breakdown structure (WBS), in project

management and systems engineering, is a deliverable-

oriented decomposition of a project into smaller components

Dividing complex projects to simpler and manageable tasks is

the process identified as Work Breakdown Structure (WBS).

Usually, the project managers use this method for simplifying

the project execution. In WBS, much larger tasks are broken

down to manageable chunks of work.

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Accurate and readable project organization.

Accurate assignment of responsibilities to the project team.

Indicates the project milestones and control points.

Helps to estimate the cost, time and risk.

Illustrate the project scope, so the stakeholders can have a

better understanding of the same.

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The preceding sections have dealtcomprehensively with the critical path

method. As a review, these are the steps tofollow in determining a schedule:

Complete the CPM network diagram. Label each activity with its proper description. Check network logic. Estimate activity durations. Identify each event with a unique node number

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Determine the early event times by implementing the forwardpass computations.

Determine the late event times by implementing the backwardpass computations.

Compute total, free, and independent float, and identify thecritical activities on the network.

Calculate calendar dates for event and activity times.

If project duration is not suitable, either revise the network orreschedule

the start/completions of the event & activities, and once againgo through Steps 5-8.

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If the project duration, starts, and finishes of activities are

suitable,

arrange the activities in the desired sequence, and tabulate

activity

identification, description, duration, early and late starts, early

and late finishes, and floats.

Finally, identify the critical activities.

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Includes processes required to ensure that the

project is completed within the approved budget.

Processes involved are:

A. Resource Planning

B. Cost Estimating

C. Cost Budgeting

D. Cost Control

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Involves determining what physical resources

(people, equipment, materials etc) and what

quantities of each should be used to perform project

activities.

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1. Work Breakdown Structure:

A deliverable-oriented grouping of project elements that

organizes and defines the total scope of the project. It

Identifies the project elements that will need resources.

2. Historical Information

3. Scope Statement:

Contains the project justification and the project

objectives.

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Work Breakdown Structure

Resource Requirement

Resource Rates:

scheduled or non-scheduled

Activity Duration Estimates

Historical Information

Chart of Accounts

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Analogous Estimating / Top-down Estimating:

Using the actual cost of a previous, similar project as the

basis for estimating the cost of the current project. It is less

costly but less accurate. (Rough-cost Estimate)

Parametric Modeling:

Using project characteristics (parameters) in a

mathematical model to predict project costs.

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Cost Baseline

A time-phased budget that will be used to measure and

monitor cost performance on the project. It is

developed by summing estimated costs by period and

is usually displayed in the form of an S-curve.

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Cost Control is concerned with

(a) Influencing the factors which create changes to thecost baseline to ensure that changes are beneficial.(b) Determining that the cost baseline has changed(c) Managing the actual changes when and as they occur

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An element of work performed during the course

of a project.

An amount of work that can be identified so that

we know what it involves and can recognize,

when it starts and finishes.

An activity normally has an expected duration, an

expected cost, and expected resource

requirements

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In the process of planning alternatives are examined and the

best alternative is chosen. The goal of planning is to minimize

resource use (cost) while satisfactorily completing the task .

Efficient use of equipments , material , labor and ensuring

coordinated effort are the basic aim . The outcome of planning

is predetermined course of action. Thus, the planning creates

an orderly sequence of events, defines strategies to be

followed in carrying forth the plan and describes ultimate

disposition of the result. Putting the various activity of the

project in the sequence on the time frame is the process of

scheduling . Scheduling is required for continuous checking of

the project (control), for resource mobilization , to minimize

the cost and use of resources optimally.

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Various scheduling techniques have been employed to plan the

activity in sequence in project management . In construction

project , bar chart and critical path method (CPM) have been

widely used . During the planning process , a manager builds

the facilities on paper , thus identities each of the various tasks

and time .During construction , these predetermined course of

action form the basis for monitoring and the checking the

progress of the work . Following steps are followed during

planning , scheduling and control .

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Identifying and defining activity

Defining activity interdependence

Estimate time and resources for each activity

Constructing the network,

Calculations on network for project time earliest start and

finish of activity, resource requirement, etc,

Project control and project review .

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In the network, it is important to know the criticality of theactivity, time available to perform the activity provided date ofcompletion of a project. In the previous section we havealready talked about various method of obtaining activityduration. We shall be interested in the question that

How early we can start the activity. How much we can delay the activity such that target date of

completion of project is not affected What the time available to perform the activity.

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Early start time

Early finish time

Latest start time

Latest finish time

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It is the earliest time by which an activity can started.

Let tij be the activity between events i and j. Let T Ei is the

earliest expected time of the event i then

Earliest start time is equal is to

EST = T Ei

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The earliest finish time of an activity is the time by which an

activity can be finished earliest. The earliest finish time of an

activity is earliest start time plus activity duration.

EFT = EST + activity duration

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The latest finish time is the time by which an activity must be

finished such that completion of the project is not delayed the

latest finish time of an activity between events i and j is the

latest allowable event time of

LFT= T Lj

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The latest start time is the time by which an activity

must start such that completion of project is not

delayed. The latest start time of an activity between

events i and j is latest finish time minus activity

duration.

LST = LFT – activity duration

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In the last reading we have discuss that in the project with art

interested in time available to execute particular task(activity)

during the project period. We shall introduce the concept float

which tells us how much an activity can fluctuate without

affecting the completion of a project. We shall introduce

following float

Total float.

Free float.

Independent float.

Interfering float.

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Total float is the maximum time available during which an

activity can fluctuate. It is maximum time available minus

activity duration. The maximum time available in the

difference between latest finish time minus earliest start

time.

Maximum time available to execute the work = LFT – EST

total float = maximum time avalable – activity duration

= LFT – EST - t ij

= LST – EST

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Free float is the time available to fluctuate the activity without

the affecting the succeeding activity. The mean of without

affecting succeeding activity is that the activity must finish

before the earliest occurrence of the head event.

Time available = T Ei – EST

Free float = Time available – activity duration

= T Ei – EST - T E

ij

Free float = T Ei – EFT

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It is the time available to fluctuate if the precedingactivities get completed as late as possible and succeedingactivities get started as early as possible.

Hence time available = Tei – TL

i

Independent float =Minimum time available – activityduration

= T Ei – T L

i - T Eij

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Interfering float is defined as difference

between total float and free float.

I.F=T.F-F.F

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Find critical path

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3

2 7

4

1 86

5

8-10-12

3-7-9 8-10-12

4-6-8

3-5-6

7-10-15

5-8-12

Path A 1-2-7-8

Path B 1-2-6-8

Path C 1-3-6-8

Path D 1-4-5-6-8

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Path Optimistic time Most likely time Pessimistic time

Path A 1-2-7-8 19 26 35

Path B 1-2-6-8 17 26 40

Path C 1-3-6-8 18 27 36

Path D 1-4-5-6-8 19 28 39

Expected time for each activity

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6

4 PLoE

tttt

PATH ACTIVITY to tL tP tE ∑tE

A

1-2 6 8 11 8.17

26.342-7 8 10 12 10

7-8 5 8 12 8.17

B

1-2 6 8 11 8.17

26.832-6 4 8 14 8.33

6-8 7 10 15 10.33

C

1-3 3 7 9 6.67

273-6 8 10 12 10

6-8 7 10 15 10.33

D

1-4 5 7 10 7.17

28.334-5 4 6 8 6

5-6 3 5 6 4.83

6-8 7 10 15 10.33

Path ‘D’ is critical path

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