developing a network plan - cpm

6. 1 Project Management Gürkan Kumbaroğlu - Bogaziçi University

Developing a Network Plan The Project Network

• The project network is developed from the information

collected for the WBS and is a graphic flowchart of the

project job plan.

– It is the tool for planning, scheduling, monitoring project progress.

• The network depicts, – project activities that must be completed;

– the logical sequences;

– the interdependencies of the activities to be completed;

– the times for the activities to start and finish;

– the longest path through the network (the critical path).

• The project network represents three quarters of the

planning process.

6. 2 Project Management


• The network provides valuable information & insights:

– Planning

* Provides realistic, simple & disciplined basis for attaining objectives;

* Reduces the risk of overlooking tasks;

* Facilitates longer range and more detailed planning of projects;

* Provides a basis for scheduling labor and equipment;

* Provides an estimate for project duration;

* Indicates activities’ start/finish times and when they can be delayed;

* Provides the basis for budgeting the cash flow of the project.

– Communication

* Provides documentation & facilitates communication of project info;

* Enhances communication that melds all managers & groups together;

* Simplifies coordination at all levels of management.

Gürkan Kumbaroğlu - Bogaziçi University



• The network provides valuable information & insights:

– Psychological

* Encourages a team feeling;

* Useful in establishing interim schedule objectives and in delineation

of responsibilities to achieve them;

– Control

* Identifies which activities should not be delayed;

* Highlights activities to consider if the project needs to be compressed

* Facilitates the application of management by exception;

* Immediately illustrates the effects of technical & procedural changes;

* Minimizes surprises.

– Training

* Useful in training new project managers and other personnel.



B

A

C

D

E

F

Level 1 - Milestone Plan

Level 2 - Plans

Level 3 - Plans

Developing a Network Plan From Work Package to Network

WP -1 WP -2 WP -3



Developing a Network Plan From Work Package to Network

Circuit

Board

Design cost

account

Production cost

account

Test cost

account

Software cost

account O r

g a

n i

z a

t i

o n

a l

U

n i

t s

Design WP D-1-1 Specifications WP D-1-2 Documentation

Production WP P-10-1 Proto 1 WP P-10-2 Final Proto 2

Test Systems WP T-13-1 Test

Software WP S-22-1 Prem Sftware WP S-22-2 Final Sftware

Lowest

Element A

D-1-1

D-1-2

B

P-1O-1

C

S-22-1

D

P-10-2

F

S-22-2

K

T-13-1

A

Spec & Docum

2

B

Proto 1

5

C

Prelim Software

3

D

Final Proto 2

4

F

Final Software

2

K

Test

3



• Activity: An element of the project that requires time.

• Merge Activity: An activity that has more than one activity immediately preceding it.

• Burst Activity: An activity that has more than one activity immediately following it.

• Parallel Activities: Activities that can take place concurrently.

• Path: A sequence of connected, dependent activities.

• Critical Path: It is a longest path through the network.

• Event: It is a point in time when an activity is started or completed.

• Activity-on-Node Networks: Node represents activities.

• Activity-on-Arrow Networks: Arrow represents activities.

Developing a Network Plan Constructing a Project Network



Basic Rules to Follow in Developing Project Networks:

1. Networks flow typically from left to right;

2. An activity cannot begin until all preceding activities have been completed;

3. Arrows indicate precedence and flow; arrows can cross over each other; their lengths and slopes are arbitrary;

4. Each activity should have a unique identification number;

5. An activity identification number must be larger than that of any activities that precede it;

6. Looping is not allowed;

7. Conditional statements are not allowed;

8. There should be a single start node and a single end node.

Developing a Network Plan Constructing a Project Network



Developing a Network Plan Activity-on-Node Fundamentals

A B C

Z

X

Y

L

K M

J

AA

X Z

Y

A is preceded by nothing; B is preceded by A; C is preceded by B.

Y and Z are preceded by X;

Y and Z can occur concurrently, if so desired;

X is a burst activity; Y, Z are parallel activities

J, K, L can occur concurrently, if so desired;

J, K, L must all be completed before M can begin;

M is a merge activity; J, K, L are parallel activities;

M could also be a milestone.

Z is preceded by X and Y;

AA is preceded by X and Y;

Z and AA can occur concurrently, if so desired.



Developing a Network Plan Activity-on-Node Fundamentals

KOLL Business Center - Network Information

Activity Description Preceding Activity Activity Duration

A Application approval None 5 B Construction plans A 15 C Traffic study A 10 D Service availability check A 5 E Staff report B, C 15 F Commission approval B, C, D 10 G Wait for construction F 170 H Occupancy E, G 35


A

Application approval

B

Construction plans

C

Traffic Study

D

Service avail check

E

Staff report

F

Commission approval

G

Wait construction

H

Occupancy


Developing a Network Plan Network Computation Process

• Forward Pass—Earliest Times

– How soon can the activity start? (early start—ES)

– How soon can the activity finish? (early finish—EF)

– How soon can the project finish? (expected time—ET)

• Backward Pass—Latest Times

– How late can the activity start? (late start—LS)

– How late can the activity finish? (late finish—LF)

– Which activities represent the critical path?

– How long can it be delayed? (slack or float—SL)




Forward Pass Computations

• Add activity times along each path in the network

(ES + Duration = EF).

• Carry the early finish (EF) to the next activity where

it becomes its early start (ES) unless…

• The next succeeding activity is a merge activity, in

which case the largest EF of all preceding activities

is selected.




Applictn approval

0 A 5

5

Construct plans

5 B 20

15

Traffic study

5 C 15

10

Commisn approval

20 F 30

10

Wait constructn

30 G 200

170

Staff report

20 E 35

15

Occpancy

200 H

235

35

Service check

5 D

10

5

Description SL

ES ID EF

LS Dur LF

Legend

Forward Pass Computations



Backward Pass Computations


• Subtract activity times along each path in the

network (LF - Duration = LS).

• Carry the late start (LS) to the next activity where it

becomes its late finish (LF) unless

• The next succeeding activity is a burst activity, in

which case the smallest LF of all preceding activities

is selected.



Applictn approval

0

0 A 5

0 5

5

Construct plans

0

5 B 20

5 15 20

Traffic study

5

5 C 15

10 10

20

Commisn approval

0

20 F 30

20 10 30

Wait constructn

0

30 G 200

30 170 200

Staff report

165

20 E 35

185 15

200

Occpancy

0

200 H

235

200 35 235

Service check

10

5 D

10

15 5 20 Description SL

ES ID EF

LS Dur LF

Legend







• Free Slack

– The amount of time an activity can be delayed without

delaying any immediately following (successor) activity.

• Total Slack (or just Slack)

– The amount of time an activity can be delayed without

delaying the entire project.

• The critical path is the network path(s) that has

(have) the least slack in common.



Applictn approval

15

0 A 5

15 5

20

Construct plans

15

5 B 20

20 15 35

Traffic study

20

5 C 10

25 10

35

Commisn approval

15

20 F 30

35 10 45

Wait constructn

15

30 G 200

45 170 215

Staff report

180

20 E 35

200 15

215

Occpancy

15

200 H

235

215 35 250

Service check

25

5 D

10


ES ID EF

LS Dur LF

Legend

Externally Imposed Deadline > Expected Completion Time




Applictn approval

- 5

0 A 5

- 5 5

0

Construct plans

- 5

5 B 20

0 15 15

Traffic study

0

5 C 10

5 10

15

Commisn approval

- 5

20 F 30

15 10 25

Wait constructn

- 5

30 G 200

25 170 195

Staff report

160

20 E 35

180 15

195

Occpancy

- 5

200 H

235

195 35 230

Service check

5

5 D

10


ES ID EF

LS Dur LF

Legend

Externally Imposed Deadline < Expected Completion Time




• Network Logic Errors – Conditional statements;

– Looping.

• Activity Numbering: Each activity needs a unique ID code.

• Use of Computers – Computations, Data storage and updating, Network development

• Calendar Dates – Ultimately they must be deployed;

– Most computer programs will do it automatically.

• Multiple start and/or end activities – Some computer programs require a common start and finish;

– Dangler paths are confusing at best;

– Dangler paths can be avoided by defining specific start, finish

nodes.

Developing a Network Plan



Developing a Network Plan Gantt Charts

15

10

5

10

5

170

35

5

50 100 150 200 235

Application approval

Construction plans

Traffic study

Service check

Staff report

Commission approval

Wait for construction

Occupancy

Gantt Chart of the Koll Business Center Project

(where every activity is scheduled to start at its earliest start time)



Developing a Network Plan Extended Network Techniques

B1

Lay Pipe 1/3

A1

Trench 1/3

A2

Trench 1/3

A3

Trench 1/3

B2

Lay Pipe 1/3

B3

Lay Pipe 1/3

C1

Refill 1/3

C2

Refill 1/3

C3

Refill 1/3

Example of Laddering Using Finish-to-Start Relationships (a pipe laying project)



A Lag is the minimum amount of time a dependent activity must be

delayed to begin or to end.

• Finish-to-Start Relationships offer the ability to delay the next

activity in a sequence even when the preceding activity is completed.


X Y

Finish-to-Start

Relationship

Lag 2


e.g. it takes two days for transport


• Start-to-Start Relationship typically depicts a situation in which a

portion of one activity is performed and the successor activity is

initiated before completing the first.


Trench

1 mile

Lay pipe 1 mile

Lag 3

Start-to-Start

Relationship



• Finish-to-Finish Relationship is used when the finish of one activity

depends on the finish of another activity.


Prototype

Testing

Lag 4

Finish-to-Finish

Relationship



• Start-to-Finish Relationship is used when the finish of one activity

depends on the start of another activity.


Testing

System document

Lag 3

Start-to-Finish

Relationship



Developing a Network Plan Extended Techniques Example

Legend

Lag 10

Lag 5

Lag 5

Lag 10

Lag 10

ES ID EF

SL SL

LS LF Dur

15 C 20

5 5

20 25 5

15 E 30

0 0

15 30 15

5 B 15

0 0

5 15 10

0 A 5

0 0

0 5 5

10 D 25

11 11

21 36 15

30 F 40

0 5

30 45 10

40 H 50

5 0

45 50 5

25 G 40

11 0

36 40 4



Wind Energy Plan Project Activity Durations and Precedence Relationships



Wind Energy Plan Project The Project Network

2

A

C

G

E

D

L

K

H

F

I

J

M

N

Start

B

Finish

2

1



Wind Energy Plan Project The Project Network

Activity Duration Early Early Late Late Slack

Code (month) Start Finish Start Finish

A 2 0 2 0 2 0

B 12 0 12 0 12 0

C 2 0 2 0 2 0

D 2 2 4 2 4 0

E 4 2 6 3 7 1

F 4 4 8 4 8 0

G 3 2 5 4 7 2

H 5 4 9 5 10 1

I 3 5 8 5 10 0

J 3 7 10 7 10 0

K 6 2 8 5 11 3

L 9 2 11 2 11 0

M 1 10 11 10 11 0

N 1 11 12 11 12 0



Wind Energy Plan Project The Gantt Chart

Activity Time Plan (months)

Code 1 2 3 4 5 6 7 8 9 10 11 12

A

B

C

D

E

F

G

H

I

J

K

L

M

N



Air Control Project The Project Plan



Air Control Project MS Project Output



Activity On Arc Rules


1. Node 1 represents the start of the project. An arc should lead from node 1

to represent each activity that has no predecessors

2. A finish node representing the completion of activities should be included

3. Nodes should be numbered successively

4. An activity should not be represented by more than one arc in the network

5. Two nodes can be connected by at most one arc


Activity On Arc Example


Activity Predecessors Duration (days)

A - 6

B - 9

C A, B 8

D A, B 7

E D 10

F C, E 12

ET(i): Early event time; earliest time at which the event corresponding to node i can occur

LT(i): Late event time; latest time at which the event corresponding to node i can occur

TS(i,j) = LT(j) – ET(i) – dij

FS(i,j) = ET(j) – ET(i) – dij


References:

• Larson E. W and Gray C. F., “Project Management: The

Managerial Process”, 5th ed. Mc Graw Hill/Irwin, NY, USA, 2011

• Winston, L.W., “Operations Research: Applications and

Algorithms” 4th ed. Duxbury Press, 2003.

• Original slides courtesy of Prof. Ilhan Or.


developing a network plan - cpm

Documents

project network

project activities

network wp

project management activity

network plan

project duration

project progress

project needs