© 2004 by prentice hall, inc., upper saddle river, n.j. 07458 3-1 network planning methods example...

© 2004 by Prentice Hall, Inc., Upper Saddle River, N.J. 074583-1

Network Planning Methods Network Planning Methods Example CPM : Saint Paul’s Example CPM : Saint Paul’s

Hospital Hospital

CPM and PERT

CPM (Critical Path Method) and PERT (Program Evaluation and Review Technique) are network based methods designed to assist in the planning, scheduling, and control of projects. A project is a collection of interrelated activities with each activity consuming time and resources. The objective of CPM and PERT is to provide analytic means for scheduling the activities.


Terms Used in Project Management Terms Used in Project Management

Activity : A certain amount of work or task required in the project

Activity duration: In CPM the best estimate of time to complete an activity . In PERT the expected time or average time to complete an activity

Critical activity : An activity that has no room for schedule slippages : if it slips the entire the entire project completion will slip. An activity with zero slack


Terms Used in Project Terms Used in Project Management .contManagement .cont

Critical path: The chain of critical activities for the project .The longest path through the network

Dummy activity :An activity that consumes no time but shows precedence among activities

Earliest finish (EF): The earliest that an activity can finish from the beginning of the project

Earliest start ( ES): The earliest that an activity can start from the beginning of the project



Event :A beginning , a completion point ,or a milestone accomplishment within the project . An activity begins and ends with events

Latest finish (LF) : The latest that an activity can finish from the beginning of the project

Latest start (LS) :The latest that an activity can start from the beginning of the project



Predecessor activity : An activity that must occur before another activity .

Slack : The amount of time that an activity or group of activities can slip without causing a delay in the completion of the project

Successor activity : An activity that must occur after another activity



Conventions used in drawing network diagrams (Arrows & Circles )

Activity on Arrow (AOA) : The activities are denoted by Arrows and events are denoted by circles

Activity on Node(AON) : Activities are denoted by circles(or nodes) and the precedence relation ships between activities are indicated by arrows


Relationship between activities Project duration Critical path Slack for non – critical activities Crashing (cost / time trade-offs) Resource usage

Network planning methods that generate:Network planning methods that generate:


St. Paul’s HospitalSt. Paul’s Hospital

ImmediateActivity Description Predecessor(s)

A Select administrative and medical staff.B Select site and do site survey.C Select equipment.D Prepare final construction plans and layout.E Bring utilities to the site.F Interview applicants and fill positions in nursing,

support staff, maintenance, and security.G Purchase and take delivery of equipment.H Construct the hospital.I Develop an information system.J Install the equipment.K Train nurses and support staff.

——ABB

ACDAE,G,HF,I,J






——ABB

ACDAE,G,HF,I,J

AON Network

FinishStart

A

B

C

D

E

F

G

H

I

J

K






——ABB

ACDAE,G,HF,I,J

Completion Time

FinishStart

K9

I15

F10

C10

D10

E24

G35

H40

J4

A12

B9






——ABB

ACDAE,G,HF,I,J

Completion Time

FinishStart

K9

I15

F10

C10

D10

E24

G35

H40

J4

A12

B9

Path Expected Time (wks)

A-I-K 36A-F-K 31A-C-G-J-K 70B-D-H-J-K 72B-E-J-K 46

CriticalPath


Critical PathCritical Path The longest path in the network Defines the shortest time project can be completed Critical path activity delay project delay


Begin at starting event and work forward ES is earliest start

ES = 0 for starting activities ES = Maximum EF of all

predecessors for non-starting activities

EF is earliest finish EF = ES + Activity time

Earliest Start and Earliest FinishEarliest Start and Earliest Finish

ESES

LS

EFEF

LF

Activity Name

Activity Duration


A

12

K

9

C

10

G

35

J

4

H

40

B

9

D

10

E

24

I

15

F

10

FinishStart

Earliest Start / Earliest FinishEarliest Start / Earliest Finish


Earliest Start / Earliest FinishEarliest Start / Earliest Finish

Finish

Earliest start time Earliest finish time

A

12

K

9

C

10

G

35

J

4

H

40

B

9

D

10

E

24

0 12

I

15

F

10

12 27

12 22 63 72

22 57

59 6319 59

9 33

0 9 9 19

12 22

Critical path

Start


Begin at ending event and work backward LF is latest finish

LF = Maximum EF for ending activities

LF = Minimum LS of all successors for non-ending activities

LS is latest start LS = LF – Activity time

Latest Start and Latest FinishLatest Start and Latest Finish

ES

LS

EF

LF

Activity Name

Activity Duration


Latest Start / Latest FinishLatest Start / Latest Finish

A

12

K

9

C

10

G

35

J

4

H

40

B

9

D

10

E

24

0 12

I

15

F

10

12 27

12 22 63 72

22 57

59 6319 59

9 33

0 9 9 19

12 22

48 63

2 14 53 63 63 72

14 24 24 59

0 9 9 19 19 59

35 59

59 63

Latest start time Latest finish time

Critical path

FinishStart

What do you notice about ES/LS & EF/LF?


Activity Slack AnalysisActivity Slack Analysis

A

12

K

9

C

10

G

35

J

4

H

40

B

9

D

10

E

24

0 12

I

15

F

10

12 27

12 22 63 72

22 57

59 6319 59

9 33

0 9 9 19

12 22

48 63

2 14 53 63 63 72

14 24 24 59

0 9 9 19 19 59

35 59

59 63


Critical path

FinishStartSlackK = 63 – 63 = 0

or

SlackK = 72 – 72 = 0

Slack = LS – ES

or

Slack = LF – EF


Activity Slack AnalysisActivity Slack Analysis

A

12

K

9

C

10

G

35

J

4

H

40

B

9

D

10

E

24

0 12

I

15

F

10

12 27

12 22 63 72

22 57

59 6319 59

9 33

0 9 9 19

12 22

48 63

2 14 53 63 63 72

14 24 24 59

0 9 9 19 19 59

35 59

59 63


Critical path

FinishStart

Node Duration ES LS Slack

A 12 0 2 2BB 99 00 00 00C 10 12 14 2DD 1010 99 99 00E 24 9 35 26F 10 12 53 41G 35 22 24 2HH 4040 1919 1919 00I 15 12 48 36JJ 44 5959 5959 00KK 66 6363 6363 00

Activity slack = maximum delay time

Critical path activities have zero slack


Activity SlackActivity Slack

How much would we like to reduce the time for activity B?

C

15

5 20

10 25

A

5

0 50 5

FinishStart

B

20

5 25

5 25D

10

25 35

25 35

A critical path of the project is a path comprising of critical activities of the project.

It is to be remembered that

• a project can have more than one critical path,

• Any critical path will start at node 1 and will end at node n and that

• The sum of the durations of the activities lying on a critical path is the duration of the project.

© 2004 by prentice hall, inc., upper saddle river, n.j. 07458 3-1 network planning methods example...

Documents

activity critical activity

project management activity

project activity duration

project successor activity

prentice hall

upper saddle river

contpredecessor activity

activity consuming time