Activity on the Node

8/7/2019 Activity on the Node

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PPrecendance diagramsrecendance diagrams Unlike Arrow Diagramming that uses the

arrows for activities and nodes for thestart and end of activities, Precedence

Diagramming places the activity on thenodes and uses arrows between thenodes to show the sequence betweeneach activity

Precedence Diagramming is also called"activity-on-the-node"


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AdvantagesAdvantages Physically easier to produce and require far

less draughtsman ship

The need for dummy activities is eliminated

Additional information can be inserted in the

network without affecting the legibility ofthe finished plan

They allow a closer co-ordination betweenthe network and the resultant linked barchart

Time delays can be introduced easier thanwith arrow networks


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EExamplexample 11


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Example 2Example 2


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Example 3Example 3


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Example 4Example 4


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Example 5Example 5


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Example 6Example 6

:OTE You can say that&activities A B merge at D


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Layout of activity boxesLayout of activity boxes

ActivityRef No

Duration

EST

LST

EFT

LFT


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AnalysisAnalysis

Forward passTo obtain EST

All projects may be assumed to start

from day 1 unless specifiedotherwise (due to weather conditions). Alternatively, you can assume

the start as day 0


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Example 7Example 7

A

5

1 6 B

3

6 9 C

10

9 19


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Example 8Example 8

A

5

1 6

B

6

1 7

C

2

D

8

E

2


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Example 8Example 8A

5

1 6

B

6

1 7

C

2

6 8

D

8

7 15

E

2

7 9

We know that an activitycannot start until all

the activities leading toit have completed

Whenever there is morethat one activity

preceding a selected,activity the Early Start

Time of the selectedactivity is the latest of

the preceding EarlyFinish Times

{ , }Max 7 6


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AnalysisAnalysis

Backward passTo obtain LST


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Example 9Example 9

A

5

1 6 B

3

6 9 C

10

9 19


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Example 9Example 9

A

5

1 6 B

3

6 9 C

10

9 19

19

,Once the last activity s Late Finish Time has been set then youcan calculate the activity s Late Start Time by subtracting the

, . . ,activity duration from the Late Finish Date i e for activity C= - =LST 19 10 9

As you proceed through the schedule the Late Finish Time of apreceding activity is the earliest of the prior Late Start Times


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Example 9Example 9

A

5

1

1

6

6

B

3

6

6

9

9

C

10

9

9

19

19

- =9 3 6- =6 5 1 - =19 10 9


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Example 10Example 10

A

5

1

2

6

7

B

6

1

1

7

7

C

2

6

13

8

15

D

8

7

7

15

15

E

2

7

13

9

15

{ , }Min 13 7- =7 6 1


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Start to start logicStart to start logic

The standard sequence where oneactivity precedes another is calledFinish-to-Start

Use the Start-to-Start sequence when

the start of the following activities isdependant upon the start of the

following activity

The Start-to-Start sequence has itsimpact on the forward passcalculations


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NoteNoteNotice that the logic sequence between

activities using the Start-to-Startsequence may include a timecomponent.

For example, we cannot start the pipe

installation at exactly the same as thestart of the trenching operation. The

first activity must get ahead a fewdays, before the piping activity canbegin. Adding a time duration to thesequence between activities is a majorinnovation associated with the

Precedence Diagram


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Example of start-to-startExample of start-to-start An example use of the Start-to-Start

sequence is that of laying undergroundpipe. In such a project a machine digs atrench in which the pipe is placed. Once the

pipe is placed, then the same machine maybe used to backfill the trench. An effectiveproject manager may want to schedule thisproject such that the pipe installation canproceed before the whole trench has been

cut. Similarly, the backfill could beginbefore the entire length of pipe has beeninstalled. To show how the start of oneactivity can affect the start of another, usethe Start-to-Start sequence.


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Example of start-to-startExample of start-to-start

A

5

1 6

B

6

3

C

2

D

8

E

2

SS2


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A

5

1 6

B

6

3 9

C

2

6 8

D

8

9 17

E

2

9 11

SS2


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A

5

1

4

6

9

B

6

3

3

9

9

C

2

6

15

8

17

D

8

9

9

17

17

E

2

9

15

11

17

SS2


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A

5

1

4

6

9

B

6

3

3

9

9

C

2

6

15

8

17

D

8

9

9

17

17

E

2

9

15

11

17

SS2

:NOTEThe critical path begins with thestart of Activity A


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Finish to finish logicFinish to finish logic

Finish-to-Finish can be thought of aslinking the completion of twoactivities such that the completion of

the prior activity takes place a fewdays before the completion of thesecond activity


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Example of finish to finishExample of finish to finish

Completion of the pipe installationcannot occur until some time afterthe completion of the trenching

activity.

The pipe must all be installed prior to

the completion of the backfill activity


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A

5

1 6

B

6

1 7

C

2

6 8

D

8

7 15

E

2

7 9

FF5

FF2


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A

5

1 6

B

6

1 7

C

2

6 8

10

D

8

7 15

15

E

2

7 9

13

FF5

FF2


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A

5

1 6

B

6

1 7

C

2

6

8

8

10

D

8

7

7

15

15

E

2

7

11

9

13

FF5

FF2


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A

5

1 6

7

B

6

1 7

7

C

2

6

8

8

10

D

8

7

7

15

15

E

2

7

11

9

13

FF5

FF2


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Exercise 1Exercise 1

A

1START

B

3

C

2

F

5END

D

2

H

1

J

3

E

4

G

1


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Solution 1 (forward)Solution 1 (forward)

A

1

0 1START

B

3

1 4 C

2

4 6 F

5

8 13END

D

2

0 2

H

1

0 1 J

3

2 5

E

4

4 8 G

1

8 9


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Solution 1 (backward)Solution 1 (backward)

A

1

0

0

1

1START

B

3

1

1

4

4

C

2

4

6

6

8

F

5

8

8

13

13END

D

2

0

2

2

4

H

1

0

9

1

10

J

3

2

10

5

13

E

4

4

4

8

8

G

1

8

12

9

13

Documents

Activity on the Node