Large Scale Systems Design
G52LSS
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 staff
profile and staff utilisation for a project following the Gantt chart
and staff requirements.
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
1
Gantt Charts
A project schedule represents the sequencing of the
project activities and milestones in a clear and logical
manner to facilitate project execution and control.
After the PERT/CPM analysis is completed, the
following phase is to construct the GANTT chart and
then to re-allocate resources and re-schedule if
necessary.
A GANTT chart is a useful graphical tool to aid project
management. In a Gantt chart tasks are represented as
horizontal bars.
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
2
Characteristics of Gantt Charts
•
The bar in each row identifies the corresponding task
•
The horizontal position of the bar identifies start and end times
of 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
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
3
Early start GANTT chart – the bar of each activity
begins at the activity earliest start time (ES).
A
B
C
D
E
F
G
0
1
2
3
4
5
University of Nottingham
School of Computer Science
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7
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Large Scale Systems Design
Dr Dario Landa-Silva
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Late start GANTT chart – the bar of each activity ends
at the activity latest finish time (LF).
A
B
C
D
E
F
G
0
1
2
3
4
5
University of Nottingham
School of Computer Science
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Large Scale Systems Design
Dr Dario Landa-Silva
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Constructing Gantt Charts
The steps to construct an early Gantt chart using the
information obtained from the PERT/CPM analysis are
as follows:
1.
2.
3.
4.
Schedule the critical tasks in the correct position
Place the time windows in which the non-critical
tasks can be scheduled (ES and LF)
Schedule the non-critical tasks according to their
earliest starting (ES) times
Indicate precedence relationships between tasks
Note: to construct a late Gantt chart use the latest
starting (LS) time to schedule non-critical tasks.
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
6
Example 8.1 Construct an early Gantt chart for the
following project.
A(3)
3/6
C(5)
11/11
G(3)
D(7)
0/0
B(4)
Task
A
B
C
D
E
F
G
4/4
E(2)
Precedence Duration
3
4
A
5
B
7
B
2
E
4
C,D
3
University of Nottingham
School of Computer Science
ES
0
0
3
4
4
6
11
14/14
F(4)
6/10
EF
3
4
8
11
6
10
14
LS
3
0
6
4
8
10
11
Large Scale Systems Design
Dr Dario Landa-Silva
LF
6
4
11
11
10
14
14
Slack
3
0
3
0
4
4
0
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Example 8.1 (cont.)
Step 1
A
B
C
D
E
F
G
0
1
2
3
4
5
University of Nottingham
School of Computer Science
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Large Scale Systems Design
Dr Dario Landa-Silva
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Example 8.1 (cont.)
Step 2
A
B
C
D
E
F
G
0
1
2
3
4
5
University of Nottingham
School of Computer Science
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7
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Large Scale Systems Design
Dr Dario Landa-Silva
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Example 8.1 (cont.)
Step 3
A
B
C
D
E
F
G
0
1
2
3
4
5
University of Nottingham
School of Computer Science
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Large Scale Systems Design
Dr Dario Landa-Silva
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Example 8.1 (cont.)
Step 4
A
B
C
D
E
F
G
0
1
2
3
4
5
University of Nottingham
School of Computer Science
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7
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Large Scale Systems Design
Dr Dario Landa-Silva
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Example 8.2 Construct a late Gantt chart for the
following project.
0/3
A(3)
2/5
3/8
B(5)
5 / 10
10 / 14
E(4)
12 / 16
14 / 17
F(3)
16 / 19
0/0
Start
0/0
19 / 24
H(5)
19 / 24
0 / 10
C(10)
0 / 10
University of Nottingham
School of Computer Science
10 / 17
D(7)
10 / 17
24 / 27
I(3)
24 / 27
27 / 27
End
27 / 27
17 / 19
G(2)
17 / 19
Large Scale Systems Design
Dr Dario Landa-Silva
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Example 8.2 (cont.)
Step 1
Step 2
Step 3
Step 4
A
B
C
D
E
F
G
H
I
0
1
2
3
4
5
6
7
University of Nottingham
School of Computer Science
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Large Scale Systems Design
Dr Dario Landa-Silva
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Staff Profile and Utilisation
The staff profile, showing the overall staff needs during
the 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 average
efficiency in which the available staff hours are being
utilised during the project.
Resource smoothing if often used to re-allocate resources
and re-schedule activities when staff (or other resources)
is not available at the required level. The non-critical
tasks are re-scheduled within their time window
avoiding as much overlap as possible.
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
14
The staff profile is a graph that gives the total required
staff at every time in the project.
The staff utilisation is calculated by dividing the area of
staff requirements by the area inside the staff profile
envelope.
n
Staff Utilisation 
t s
i 1
i i



max  si  L
l 1L
 iAl 
where n is the number of activities
ti is the duration of activity i
si is the staff requirements of activity i
Ai is the set of activities being executed at time l
L is the duration of the project
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
15
Example 8.3 Obtain the staff profile and staff utilisation
for the following project.
7
6
5
Task
Duration
A
B
C
D
E
F
G
3
4
5
7
2
4
3
Required
Staff
2
4
1
3
1
2
5
4
A
3
B
C
2
D
E
1
F
G
0 1 2 3 4 5
6 7 8 9 10 11 12 13 14 15
University of Nottingham
School of Computer Science
0
1
2
3
4
5
6
7
Large Scale Systems Design
Dr Dario Landa-Silva
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Example 8.3 (cont.)
Staff utilisation 
6  16  5  21  2  8  15
 0.857  85.7%
84
7
6
5
4
Task
Duration
A
B
C
D
E
F
G
3
4
5
7
2
4
3
Required
Staff
2
4
1
3
1
2
5
3
2
1
0 1 2 3 4 5
6 7 8 9 10 11 12 13 14 15
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
17
Exercise 8.1 Construct the early Gantt, staff profile and
calculate staff utilisation for the following project.
Task
A
B
C
D
E
F
G
H
I
Precedence
A(8)
0/0
C(4)
A
B,C
C
E,F
F
D,G
Duration
8
5
4
7
8
6
8
6
7
4/5
University of Nottingham
School of Computer Science
ES
0
0
0
8
5
4
13
10
21
EF
8
5
4
15
13
10
21
16
28
D(7)
8/14
B(5)
Staff
3
3
8
2
2
5
3
6
5
5/5
F(6)
E(8)
10/13
LS
6
0
1
14
5
7
13
22
21
21/21
13/13
G(8)
LF
14
5
5
21
13
13
21
28
28
Slack
6
0
1
6
0
3
0
15
0
I(7)
28/28
H(6)
Large Scale Systems Design
Dr Dario Landa-Silva
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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
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University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
19
Exercise 8.1 (cont.)
The staff profile and utilisation
Staff utilisation  0.5765  57.65%
15
14
13
12
11
10
9
8
7
6
5
4
3
2
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 29 30
University of Nottingham
Large Scale Systems Design
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School of Computer Science
Dr Dario Landa-Silva
Additional Reading
Chapter 5 of (Maylor, 2003)
Chapter 3 of (Kendall and Kendall, 2005)
University of Nottingham
School of Computer Science
Large Scale Systems Design
Dr Dario Landa-Silva
21