Showing how the Sequence Step Algorithm, a simulation-based scheduling algorithm models and solves scheduling problem of repetitive project with probabilistic activity durations and work breaks.

1. (IV) Work Breaks 1
Schedule work breaks in repetitive projects
in order to reduce project duration
Presented by
Chachrist Srisuwanrat
2008
EXAMPLE OF SCHEDULING
A REPETITIVE PROJECT WITH
PROBABILISTIC ACTIVITY DURATIONS
AND WORK BREAKS

2. (IV) Work Breaks 2
Example of a Repetitive Project with
Work Breaks
A B
C
E
D
F
G
H
J
SQS1 SQS2 SQS3 SQS4 SQS5

3. (IV) Work Breaks 3
0
1
2
3
4
5
6
7
8
9
10
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450
Time
Unit
A B C D E F G H J
Average Total Idle Time = 1 day
Average Project Duration = 449 days
Controlling Sequence
0
1
2
3
4
5
6
7
8
9
10
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450
Time
Unit
A B C D E F G H J
Average Total Idle Time = 438 days
Average Project Duration = 277 days
Early-start schedule has project duration of 277 days but also has 438 days of idle time.
SQS-AL with no work breaks has average project duration of 449 days. SQS-AL schedule with no work breaks.
--288J
--102H
--282G
--78F
--120E
--120D
--68C
--114B
--0A
Crew
Return Date
(CLT2)
Work
Break
Location
Crew
Arrival Date
(CLT1)
Activity

4. (IV) Work Breaks 4
0
1
2
3
4
5
6
7
8
9
10
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450
Time
Unit
A B C D E F G H J
Average Total Idle Time = 3 days
Average Project Duration = 376 days
Controlling Sequence
0
1
2
3
4
5
6
7
8
9
10
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450
Time
Unit
A B C D E F G H J
Average Total Idle Time = 3 days
Average Project Duration = 342 days
Controlling Sequence
SQS-AL schedule with two work breaks has average project duration of 376 days.
SQS-AL schedule with three work breaks has average project duration of 342 days.
SQS-AL schedule with two work breaks.
SQS-AL schedule with three work breaks.
--180J
--84H
254G7-G8174G
--60F
--102E
--44D
98C4-C522C
134B5-B638B
--0A
Crew
Return Date
(CLT2)
Work
Break
Location
Crew
Arrival Date
(CLT1)
Activity
--214J
--102H
288G7-G8208G
--78F
--102E
--78D
--68C
134B5-B638B
--0A
Crew
Return Date
(CLT2)
Work
Break
Location
Crew
Arrival Date
(CLT1)
Activity
B5-B6
G7-G8
C4-C5
Improve
duration
by 73 days
Improve
duration
by 107 days

5. (IV) Work Breaks 5
Method Work Break
Positions
Average
Project
Duration
Average
Total Idle
Time
Project Duration
plus
idle time
CPM - 277 438 715
SQS-AL - 449 1 450
SQS-AL* G7-G8 410 3 413
SQS-AL** G7-G8, B5-B6 376 3 379
SQS-AL*** G7-G8, B5-B6,C4-C5 342 3 345
Results from Introducing Work Breaks
• SQS-AL reduces idle time by 22 months, compared to
CPM.
• SQS-AL*** with 3 work breaks reduces project duration
by 5 months, compared to SQS-AL w/o work breaks.