spring 2008, king saud university arrow diagramming dr. khalid al-gahtani 1 network schedule...
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Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
1
Network Schedule
• Predominant Network Scheduling Techniques:– Critical Path Method (CPM)– Program Evaluation and Review Technique
(PERT)
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
2
Critical Path Method (CPM)
• CPM is a graphical network-based scheduling techniques that when applied intelligently and honestly can be an excellent tool in project management.
• The CPM uses a graphic presentation of the planned sequence of activities of a project.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
3
CPM Network
• Diagrammatically illustrates all interdependencies of the project’s activities.
• Used as a basis for:– Scheduling the total project time– Establishing priorities.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
4
CPM Network
• Can be used for integrating:– Time– Cost– Available resources
• Establishes a critical path for efficient use of resources
• Determine how much time each of the project activities may be delayed without affecting the completion time of the project as determined in objective number one.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
5
CPM Network Drawing Schemes
• Arrow Diagramming
(Activity-On-Arrow, AOA).• Node Diagramming
(Activity-On-Node, AON)
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
6
Activity-On-Arrow Method
• Arrows:– Original Network Scheduling Technique– Uses a 2 nodes scheme– Diagram easily time scaled.
• Nodes:– Commonly called events– Mark points in time– Represent the beginning or end of the time
available for a given activity.• Links:
– Represent activities
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
7
Activity-On-Arrow Method
• Dummy Activities:– Dummy Activity is a fictitious activity that has
no time duration and requires no resource utilization.
– Dummy activities used to develop correct representation.
– Always break up a dummy activity at the tail, not at the head of the arrow.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
8
Activity-On-Arrow Method
– Remove redundant dummy activities– Use unique numbering system for events.– Allow for addition of future activities– Try to number events such that the “i” node is
less than the “j” node.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
9
Drawing AOA Networks
• Prerequisites:– List of all activities comprising the project– Order of precedence of each activity– Duration estimate of each activity
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
10
Drawing AOA Networks
• Basic Rules of Network Logic1. Before an activity may begin, all activities
preceding it must be completed. (Activities with no predecessors are self-actuating when the project begins.)
2. Arrows imply logical precedence only. Neither the length of the arrow not its “compass” direction on the drawing have any significance.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
11
Example:
Activity Depends on
(Immediate Predecessor(s)) Duration (Day)
(Time to perform) a ─ 14 b ─ 3 c ─ 7 d a, b 4 e b, c 10
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
12
Bar Chart
a b c d e
14
3
18
17
7
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
13
a
b
c
d
e
Dummy
Activity on arrow
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
14
Common Errors in AOA
• Dangling (AOA only).• Looping.• Redundancy (AOA only)• Unique Activity Designation• Possible of showing Improper Logic
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
15
Dangling
6 7
9
10
8
11
12
13
(8) and (9) are left dangling as they are not the last activities.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
16
Looping
a
f g
i
e h
b d
c
Looping error results when an endless loop is shown in the diagram and you can not progress beyond it.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
17
Redundancy
2 3
4
Dummy
Dummy 2-4 is unnecessary as it is not needed for network analysis.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
18
Unique Activity Designation
10 15
11
10 15
a)
b)
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
19
Possible of showing improper Logic
15 30
20 a)
10 25
Activity A Place Concrete Slab in garage
Activity C Install prefinished
shop cabinets
Activity B Install garage
door
Activity D Install garage
opener
15 30
20 b)
10 25
20
Activity A Place Concrete Slab in garage
Activity C Install prefinished
shop cabinets
Activity B Install garage
door
Activity D Install garage
opener
In a) Activity D depends on A and B
In b) Activity D depends on B only.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
20
Possible of showing improper Logic
15 30
20 a)
10 25
Activity A Place Concrete Slab in garage
Activity C Install prefinished
shop cabinets
Activity B Install garage
door
Activity D Install garage
opener
15 30
20 b)
10 25
20
Activity A Place Concrete Slab in garage
Activity C Install prefinished
shop cabinets
Activity B Install garage
door
Activity D Install garage
opener
In a) Activity D depends on A and B
In b) Activity D depends on B only.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
21
15 45
25 a)
10 40
Activity A Install Wallboard Activity D
Paint Wall
Activity B Install vinyl
flooring Activity E
Install base trim 30
20 50
Activity C Install Carpet
Activity F Install floor registers 35
In a) Activity F depends on A, B, and C.
15 45
25 b)
10 40
Activity A Install Wallboard Activity D
Paint Wall
Activity B Install vinyl
flooring Activity E
Install base trim 31
20 50
Activity C Install Carpet
Activity F Install floor registers
35
30
In b) Activity F depends only on B and C.
Possible of showing improper Logic
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
22
15 45
25 a)
10 40
Activity A Install Wallboard Activity D
Paint Wall
Activity B Install vinyl
flooring Activity E
Install base trim 30
20 50
Activity C Install Carpet
Activity F Install floor registers 35
In a) Activity F depends on A, B, and C.
15 45
25 b)
10 40
Activity A Install Wallboard Activity D
Paint Wall
Activity B Install vinyl
flooring Activity E
Install base trim 31
20 50
Activity C Install Carpet
Activity F Install floor registers
35
30
In b) Activity F depends only on B and C.
Possible of showing improper Logic
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
23
Disadvantages of Arrow Notation
• We may need to use “dummy activities”• Project Management is done on activity
basis• Does not give all details of the activity on
network diagram• Arrow would be very long, and don’t
relate to time. The network is not time scaled
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
24
Disadvantages of Arrow Notation
3
A 6
B
C 2
9
5
Dangling possible if B dos not have successors, B dangles.
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
25
Class work#1:
Activity Depends upon Activity Depends upon A G F B A I F F A J H H A K I, J, F C B, A L G, D, E D B M K E C N L, M
Spring 2008, King Saud University
Arrow DiagrammingDr. Khalid Al-Gahtani
26
Class work#1:
A
B
F
H
C
D
E
G
I
J K
L
M
N