Network Analysis

01/05/2020

BCI Lecture 9b

Peter Considine Staffordshire University Business School 1

Network Analysis

• • •

Involves:

– Critical path analysis (CPA) – Project evaluation & review (PERT)

Used:

– When consecutive actives must be planned

Allows projection of:

– Duration of the project – Delays to estimated completion date 01/05/2020 Peter Considine Staffordshire University Business School 2

Features LFT

•

Nodes EST LFT

– Numbered to the left of a circle – Symbolise start & finish of an activity – Consecutive activities go on the same line – Simultaneous activities on in the same column – Right side – top – earliest start time – Right side – bottom – latest finish time 01/05/2020 Peter Considine Staffordshire University Business School 3

Earliest Start Time

•

Earliest that the next activity can be started

– E.G. At stage 5, the next activity can start on day 4 at the earliest

4

5

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Latest Finishing Time

•

Latest date by which the previous activity must be finished if completion date is to be met

– E.G. Everything must be ready for stage 7 by day 21 or the whole Project will be late

7

21

01/05/2020 Peter Considine Staffordshire University Business School 5

Activities

• •

Labelled using letters (A, B, C …) Duration is usually given

– E.G. Activity A takes 2 days starting at stage 1

1

0 0

A, 2

2

2

01/05/2020 Peter Considine Staffordshire University Business School 6

Schedule

01/05/2020

Activity Duration Preceding activity A B C D E F G 2 3 5 2 4 2 2 A A B C C D, E

Peter Considine Staffordshire University Business School 7

Task Analysis

• • • •

Add activity duration to previous EST Choose highest number when simultaneous activities occur Arrive at estimated completion day Calculate LFT by tracing backwards

– Deduct activity time from preceding LFT – Choose lowest number when simultaneous activities occur 01/05/2020 Peter Considine Staffordshire University Business School 8

Example Network

B,3

1

0

0 A2

2

2

2 C,5

3

5

9 D,2

4

7

7 E,4 F,2

5

11

11 G,2

6

13

13 01/05/2020 Peter Considine Staffordshire University Business School 9

Critical Path Analysis (CPA)

• •

Sequence of critical activities

– If any of these are delayed, then project will be late

Path through all points where EST=LFT

– Must start & finish exactly as planned – Others are non-critical • May overrun/delayed, without affecting completion date, but should not be ignored 01/05/2020 Peter Considine Staffordshire University Business School 10

Float

• • • •

Extent of delay/overrun allowable without extending total duration time Total float = LFT-EST But, delay/overrun in one activity alters EST of another – knock-on effect ‘Free float’ (FF)

– Allocation of float between activities – FF=EST (next activity)-activity duration-EST activity 01/05/2020 Peter Considine Staffordshire University Business School 11

Management

• •

If ‘free float’ = nil, then that activity cannot actually be delayed/overrun, even if EST

– Ensures that the project will be completed on time

If ‘free float’ exists, then labour & equipment is idle and can be re-allocated to other projects & activities

– Reduces cost and/or completion time 01/05/2020 Peter Considine Staffordshire University Business School 12

P.E.R.T.

•

Identify all activities

– Sequence them – Estimate their timings – Construct a diagram representing the above – Evaluate the network & identify the critical path (schedule) – Monitor actual performance of project against the schedule – Draw activities across a time horizon (Gantt chart) 01/05/2020 Peter Considine Staffordshire University Business School 13

Gantt Charts

• • •

Used to display the schedule over time time

– Horizontal bar chart – Float becomes explicit

Plot critical path first Then others using EST

– Creates labour/resource histogram • Shows idle resources 01/05/2020 Peter Considine Staffordshire University Business School 14

CPA Changes

•

New activity leads to new critical path

– New time critical set of activities – Iterative – Identifies the most risky & time threatening activities 01/05/2020 Peter Considine Staffordshire University Business School 15

Further Readings

•

MEREDITH, J.R. & MANTEL, S.J. 2002.

Project Management: a managerial

approach. John Wiley.

01/05/2020 Peter Considine Staffordshire University Business School 16