Large Scale Systems Design G52LSS - cs.nott.ac.uk

Large Scale Systems DesignDr Dario Landa-Silva

1University of NottinghamSchool of Computer Science

Large Scale Systems DesignG52LSS

Lecture 8 – Gantt Charts and CPM

•Gantt Charts•Constructing Gantt Charts•Staff Profile and Utilisation

Learning outcomes: interpret the information in Gantt charts;construct Gantt charts following Pert/CPM method; determine staffprofile and staff utilisation for a project following the Gantt chartand staff requirements.



A project schedule represents the sequencing of theproject activities and milestones in a clear and logicalmanner to facilitate project execution and control.

After the PERT/CPM analysis is completed, thefollowing phase is to construct the GANTT chart andthen to re-allocate resources and re-schedule ifnecessary.

A GANTT chart is a useful graphical tool to aid projectmanagement. In a Gantt chart tasks are represented ashorizontal bars.

Gantt Charts



Characteristics of Gantt Charts

• The bar in each row identifies the corresponding task

• The horizontal position of the bar identifies start and end timesof the task

• Bar length represents the duration of the task

• Offer simple and good visual communication

• Task durations can be compared easily

• Good for allocating resources and re-scheduling

• Precedence relationships is represented using arrows

• Critical activities are usually highlighted

• Slack times are represented using bars with doted lines

• Milestones can be represented by special shapes

• Minor changes in data can cause major changes in the chart



Early start GANTT chart – the bar of each activitybegins at the activity earliest start time (ES).

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



Late start GANTT chart – the bar of each activity endsat the activity latest finish time (LF).

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



The steps to construct an early Gantt chart using theinformation obtained from the PERT/CPM analysis areas follows:

1. Schedule the critical tasks in the correct position2. Place the time windows in which the non-critical

tasks can be scheduled (ES and LF)3. Schedule the non-critical tasks according to their

earliest starting (ES) times4. Indicate precedence relationships between tasks

Note: to construct a late Gantt chart use the lateststarting (LS) time to schedule non-critical tasks.

Constructing Gantt Charts



Example 8.1 Construct an early Gantt chart for thefollowing project.

0440303

Slack

141410111146

LF

111084603

LS

14106

11843

EF

11644300

ES

3427543

Duration

C,DGEFBEBDAC

BA

PrecedenceTask

D(7)0/0

3/6

4/4

11/11

6/10

14/14

B(4)

A(3)

F(4)

C(5)

G(3)

E(2)



Example 8.1 (cont.)

Step 1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



Example 8.1 (cont.)

Step 2

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



Example 8.1 (cont.)

Step 3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



Example 8.1 (cont.)

Step 4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



Example 8.2 Construct a late Gantt chart for thefollowing project.

0 / 3A(3)2 / 5

0 / 0Start0 / 0

27 / 27End

27 / 27

3 / 8B(5)5 / 10

10 / 14E(4)

12 / 16

14 / 17F(3)

16 / 19

0 / 10C(10)0 / 10

10 / 17D(7)

10 / 17

17 / 19G(2)

17 / 19

24 / 27I(3)

24 / 27

19 / 24H(5)

19 / 24



Example 8.2 (cont.)

Step 1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

A

B

C

D

E

F

G

H

I

Step 2 Step 3 Step 4



The staff profile, showing the overall staff needs duringthe project, can be obtained with the project schedule(Gantt chart) and the staff requirements of each task.

Staff utilisation gives an indication of how the averageefficiency in which the available staff hours are beingutilised during the project.

Resource smoothing if often used to re-allocate resourcesand re-schedule activities when staff (or other resources)is not available at the required level. The non-criticaltasks are re-scheduled within their time windowavoiding as much overlap as possible.

Staff Profile and Utilisation



The staff profile is a graph that gives the total requiredstaff at every time in the project.

The staff utilisation is calculated by dividing the area ofstaff requirements by the area inside the staff profileenvelope.

projecttheofdurationtheis

at timeexecutedbeingactivitiesofsettheisactivityoftsrequiremenstafftheis

activityofdurationtheisactivitiesofnumbertheiswhere

max

onUtilisatiStaff

i

i

1

1

L

lAis

itn

Ls

st

i

AiiLl

n

iii

l



Example 8.3 Obtain the staff profile and staff utilisationfor the following project.

5213142

RequiredStaff

3427543

Duration

GFEDCBA

Task7

6

5

4

3

2

1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A

B

C

D

E

F

G



Example 8.3 (cont.)

5213142

RequiredStaff

3427543

Duration

GFEDCBA

Task7

6

5

4

3

2

1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

%7.85857.084

1582215166nutilisatioStaff



Exercise 8.1 Construct the early Gantt, staff profile andcalculate staff utilisation for the following project.

E(8)0/0

8/14

4/5

21/21

10/13

28/28

C(4)

A(8)

F(6)

D(7)

G(8)5/5 13/13

B(5)

I(7)

H(6)

563522833

Staff

15282216106FH0211321138E,FG

0

306106

Slack

28

1313215514LF

21

75

14106

LS

28

101315458

EF

21

458000

ES

7

687458

Duration

D,GI

CFB,CEAD

CBA

PrecedenceTask



Exercise 8.1 (cont.)The early Gantt chart

A

B

C

D

E

F

G

H

I

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30



Exercise 8.1 (cont.)The staff profile and utilisation

151413121110987654321

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

%65.575765.0nutilisatioStaff



Additional Reading

Chapter 5 of (Maylor, 2003)

Chapter 3 of (Kendall and Kendall, 2005)

Large Scale Systems Design G52LSS - cs.nott.ac.uk

Documents

Transcript of Large Scale Systems Design G52LSS - cs.nott.ac.uk