Session20-21

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SESSIONS 20 & 21

Scheduling

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DR ASSEM AL-HAJJ, Univation, RGUProject Management and Economics. SITP-SPDC, NIGERIA

Determines how company resources should be

integrated.

Important for projecting time-phased resourceutilisation requirements.

Provides a basis for visually tracking

performance.

Serves as a master plan for information.

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Identify all major events and dates clearly.

Establish number of activities and level of

breakdown structure.Define sequence of work through a network

where interrelationships between events can be

identified.

Relate schedules directly to WBS.

Identify time constraints and resources required

for each event.

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1. Summary schedules:

for management and planners

2. Detailed schedules:

for doers and lower-level control

Most organisations develop multiple

schedules:

Provide a means to

authorise and control

manpower, inventory

investment, and cash

flow.

Provides data for

material and capacity

planning

Co-ordinate

marketing,

manufacturing,

engineering, and

finance activities

Provides an overallmeasure of

performance

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Secondary objectives of scheduling: Studying alternatives

Developing an optimal schedule

Using resources effectively

Communicating Refining the estimating criteria

Obtaining good project control

Providing for easy revisions

Primary objective of scheduling:

To co-ordinate activities in the master plan

To complete the project within time, cost, and

least risk.

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Provides top management with a means to

authorise and control manpower levels, inventory

investment, and cash flow.

Co-ordinate marketing, manufacturing,

engineering, and finance activities

Provides an overall measure of performance

Provides data for material and capacity planning

7/30/2019 Session20-21

7/27DR ASSEM AL-HAJJ, Univation, RGUProject Management and Economics. SITP-SPDC, NIGERIA

An appropriate scheduling system:-

bar charts

milestone charts network

A listing of activities at the project level or lower

The possible interrelationships between activities,

this can be accomplished by logic networks,

critical path networks, or PERT network.

Activity time estimates

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Most common techniques:

1. Gantt or bar charts

2. Milestone charts

3. Networks Programme Evaluation and Review Technique

(PERT)

The Critical Path Method (CPM)

On-the-Arrow-Diagram Method

On-the-Node-Diagram Method or Precedence DiagramMethod

4. Line of balance

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The oldest, simplest planning,

scheduling and contracting

technique.

Represents the time period

allocated to the various tasks or

activities.

An activity is a task or closely

related group of tasks whose

performance contributes tocompletion of the overall

project.

Activities are entered down the

side in chronological order.

Operatio

n

Time

Excavation

Sub-structure

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Easily understood

Extremely useful for comparing planned and actual progress Easy and quick to prepare

Require less revision and updating than other moresophisticated systems.

Logical interconnections are difficult to comprehend.

Difficult to reconstruct the logic and recognise sequence

constraints

Difficult to use for forecasting the effects that changes in a

particular activity will have on the overall schedule, or

even to project the progress of an individual activity.

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A powerful analytical tool for project planning and control.

Based on the rigorous application of logic network.

PERT Originally developed in 1958 and 1959

Introduced by the Special Projects Office of the U.S. Navy

on the Polaris Weapon System in 1958

At the same time the DuPont Company initiated theCritical Path Method (CPM) technique. This particularly

concentrated in the construction and process industries.

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Reveals interdependencies and problem areas i.e.determines where the greatest effort should be made

Can determine the probabilities of meeting a specifieddeadlines by development of alternative plans.

Ability to evaluate the effect of changes in the programme.

Allows a large amount of sophisticated data to bepresented in a well-organised diagram.

Can become very complex

More data is required for the analysis

Expensive to maintain

Best for large, complex programmes

Complicated for repetitive tasks

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PERT

Uses three time estimates Optimistic, Most-likely,

Pessimistic

Probabilistic in nature,allows us to calculate therisk in completing theproject.

Used in R&D projectswhere risks in calculatingtime durations have a highvariability.

CPM Uses one time estimate

Deterministic in nature

Used for constructionprojects that resourcedependent and based onaccurate time estimates

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All tasks must be visualised in a manner clear

enough to be put down in a network which

comprises events and activities; i.e. follow the

work breakdown structure.

Events and activities must be sequenced under a

highly logical set of ground rules.

Time estimates must be made for each activity on

the network.

Critical path and float times are computed

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Three types:

1. Mandatory dependencies- hard logic:

dependencies that cannot change2. Discretionary dependencies- soft logic: may be

at the discretion of the project manager, may

change from one project to another

3. External dependencies- may be beyond the

control of the project manager.

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A network provides the following information:

Interdependencies of activities

Project completion time

Impact of late starts

Impact of early starts

Trade-offs between resources and time

What if exercises Cost of a crash programme

Slippages in planning/performance

Evaluation of performance

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EVENTACTIVITY

EVENT

Networks are composed of events and activities

An event is the starting or ending point for a group of

activities

An activity is the work required to proceed from one event

to another.

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Job description

EVENT EVENT

Start of activity Finish of activity

i j

Duration

Well testingStart of activity Finish of activity

3 77 days

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Defining the sequence of events:

Logical flow of work is established by asking the

following questions: What job/s immediately precede this one?

What job/s immediately follow this one?

What job/s can be done concurrently?The answers to these questions are compounded in

an arrow diagram.

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ExcavateErect formwork Pour concrete

1 432

21

3

5

4

Burst point

Plaster walls

1

5

3

2Rough plumbing

4

Sink

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Length & shape of the arrow does not give anysignificant information of the activity or to theresources it consumes.

Until or unless all activities, leading to an eventare completed, the event is not completed. Noactivity can start until the proceeding events are

completed. Time Flows from left to right.

The activity is identified by its start and finishevents number.

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i j

D

E

D

E

DummyD

E

Dummy

A C

Real

dummy

10

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A

B D

C

Dummy

DB

A C

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Activities A, B, and C can start together. Once B

is complete, D can start. E can start when A is

complete, and F can start when A and D are

complete. G and H can start when B and C are

complete, and J when E, F and G are complete.

Draw the network and number the nodes.

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DR ASSEM AL-HAJJ Univation RGU

A

C

B1

E2

D3

G

H4

F5

J6 7

A, B, and C can

start together

Once B is

complete, D can

start

Once A is

complete, E can

start

F can start when

A and D are

complete

G and H can startwhen B and C arecomplete

J can start when

E, F and G are

complete

Session20-21

Documents

Transcript of Session20-21