1011 H24MPR Lecture 6 - Uncertainty in Planning

8/8/2019 1011 H24MPR Lecture 6 - Uncertainty in Planning

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Ioannes Tang

Assistant Professor

Department of Civil Engineering

Faculty of Engineering

Room: B1C21, Telephone: 03-8924 8346

Email: [email protected]

Originally prepared by

Mick Mawdesley

H24 MPR Lecture 6

Uncertainty in Planning




• The construction industry is uncertain

– It builds complex projects in uncertain

conditions

– The weather affects it

– The ground conditions affect it

– It uses materials which have properties that

are uncertain – It uses largely unskilled / low skilled workers

– It has clients who change their minds

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• Planning should reduce uncertainty but,

with all this uncertainty:

– How do we decide on durations?

– How do we decide on resources?

– How can we ensure safety?

– How do we make sure that the environment

is not adversely affected?

• Without being able to do these, we

cannot produce good plans.

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• We need good records (information)

• We need to carry out sufficient

investigations

• We have to investigate alternatives

• We have to make judgements

• We have to recognise that plans will needto be updated from time to time – control

action is necessary

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• These solutions will ‘solve’ most planning

problems and help reduce uncertainty in

construction projects

However:

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Situation 1

• Many tasks in projects have to be

repeated. e.g.

– Pile driving until a particular set is achieved

– Submission of plans for planning permission

– Development of designs until client satisfied

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Question

• How do we determine the duration of

such activities in order to plan the

project?

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Situation 2

• Consider Tingham bypass

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Say that the client has

specified:

We have to build the bypass

with bridges at both High Roadand Low Road

But we can only affect

either High Road or Low Road

at any one time – not both at

the same time.

Question:

How do we draw the network

for the project?

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Possible solution?

Start andPreparation Finish

Const. HighRoad Bridge

ReopenHigh Road

Close HighRoad

Const. LowRoad Bridge

ReopenLow Road

Close LowRoad

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Possible Solution?

• Only if:

– We use resource scheduling (but what

resources?)

– Or we use some similar methods to ensure

constraint is obeyed

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Possible Solution?

Start andPreparation Finish


ReopenHigh Road

Close HighRoad


ReopenLow Road

Close LowRoad

Which is correct?Indeed, is either correct?

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Possible Solution?

• We need a ‘Decision Box’

Start andPreparation

Finish


ReopenHigh Road

Close HighRoad


ReopenLow Road

Close LowRoad

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Possible Solution?

We need a ‘Decision Box’

Start andPreparation

Finish


ReopenHigh Road

Close HighRoad


ReopenLow Road

Close LowRoad


ReopenHigh Road

Close HighRoad


ReopenLow Road

Close LowRoad

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Possible Solution

• Eisner suggested this in the early 1960s

• How do we do the calculations?

•Very difficult!!

• Is the idea any use?

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1011 H24MPR Lecture 6 - Uncertainty in Planning

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