CM P Repetitive

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Scheduling of Repetitive Projects

13/01/2002 Emad Elbeltagi

Repetitive Projects Scheduling

Linear Projects

¾ Repetitive uniform of work (multiple houses, …)

¾ Geometrically linear (pipeline, highways,…)

¾ Some non typical units may exist

¾ Projects assumed to be comprised of n typical units

¾ Complex to schedule and monitor





Duration-driven Vs Resource-driven Schedule

Duration-driven schedule

¾

Basic units: activities, durations, relationships ¾ Resources are functions of activities durations

¾ Resources are assumed to be available

Resource-driven schedule

¾ More focus on resources

¾ Meeting a deadline

¾ Line of balance (LOB)

¾ Summary diagrams



Summary Diagrams

¾ Similar activities in all units are summarized in one activity

¾ Activity duration = duration of single unit x no of units

¾ To maintain logic: Add S-S relationships and F-F relationships

DA

LSA LFA

ESA EF A

DB

LSB LFB

ESB EFB

LagSS

LagFF





Summary Diagrams

DA

LSA LFA

ESA EF A

DB

LSB LFB

ESB EFB

LagSS

LagFF

Forward path

¾ ES B = ES A + Lag SS

¾ EF B = ES B + D B , or

¾ EF B = EF A + Lag FF

Backward path

¾ LF A = LF B – Lag FF

¾ LS A = LF A – D A , or

¾ LS A = LS B – Lag SS



Summary Diagrams

¾ 3 sequential activities A, B, & C with durations 3, 2, & 2 days

¾ 4 similar units

A1 (3)

0 3

0 3

C1 (2)

8 10

5 7

B1 (2)

6 8

3 5

A2 (3)

3 6

3 6

C2 (2)

10 12

8 10

B2 (2)

8 10

6 8

A3 (3)

6 9

6 9

C3 (2)

12 14

11 13

B3 (2)

10 12

9 11

A4 (3)

9 12

9 12

C4 (2)

14 16

14 16

B4 (2)

12 14

12 14





Summary Diagrams

C

8

A

12

B

8

Lag 2

Lag 2

Lag 2

Lag 3

0 12

3 14

5 16

168

146

120



Line of Balance (LOB)

¾ Meet deadline date

¾ Focus on resources






How Many Crews Needed to Meet Deadline ?

Crew 2

Crew 1

Crew 3

Crew 2

Crew 1

Site

5

0 1 2 3

Time

1

2

3

4

One Activity & 3 Crews












Time

1

4

5

3

6

2

9

8

7

SitesParallel Crews Diff. Durations Stagg. Crews





Line of Balance Calculations

¾

Crew synchronization and work continuity equation

¾ Computation of project delivery rate to meets a deadline

¾ Calculating resource needs

¾ Drawing the LOB schedule



Line of Balance Calculations

¾ Crew synchronization and work continuity equation

¾ Computation of project delivery rate to meets a deadline

¾ Calculating resource needs

¾ Drawing the LOB schedule





Line of Balance Calculations (work continuity)

Crew 1

Crew 3

Crew 2

Crew 1

Unit

5

0 1 2 3

Time

1

2

3

4

R

D

C Crews

R = C / D C = D x R




Crew 1

Crew 2

1

D/C D/C D/C

Crew 3

0 1 2 3

Time

3

2

1

Unit

R = 1 / (D / C) C = D x R

R R





Line of Balance Calculations (Meeting a deadline)

Time

n

.

.

.

2

1

Units

T1 = CPM Duration of Unit 1

TL = Project Deadline Duration

R

n-1

R = (n – 1) / (T L - T 1 )



Line of Balance Calculations (Meeting a deadline)

TL

- T1

n-1

Unit n

Unit 1

TF = 3 D (2)

A (5) B (5) C (5)

A (5) B (5) C (5)

D (2) TF = 3

B

(TL - T1 ) + TFD

A CD D

R = (n – 1) / (T L - T 1 ) + TF






¾ Draw the CPM for one unit and determine activities floats; TF i

¾ Calculate CPM duration for one unit; T 1

¾ Calculate R i = (n-1) / (T L - T 1 ) + TF i

¾ Calculating Number of crews needed C i = R i x D i

¾ Calculate actual number of crews C ai = Round up C i

¾

Then calculate actual delivery rates R ai = C ai / D i



Line of Balance Calculations (Example)

¾ A 5 Kilometer pipeline project

¾ The activities involved in one Kilometer is given below

¾ Project deadline 30 days

¾

Assume 2 days buffer time between activities

-

1

1

2,3

4

5

1

3

1

4

1

2

Locate and clear

Excavate

String pipe

Lay pipe

Pressure test

Backfill

1

2

3

4

5

6

Preceding activitiesDuration

(days)Activity name

Activity

no.






2 (3)

3 6

3 6

5 (1)

14 15

14 15

1 (1)

0 1

0 1

4 (4)

8 12

8 12

6 (2)

17 19

17 19

3 (1)

5 6

3 4

-2

-2-2

-2 -2 -2

T1 = 19 days

TL= 30 days

N = 5 units

R i = (n-1) / T L - T 1 + TF i = 4 / (11 + TF i )




0.510.7280.364026

110.3640.364015

0.521.4560.364044

110.3080.308213

0.66721.0920.364032

110.3640.364011

Rai = Cai / Di

Cai =

Round up Ci

Ci =Di x Ri

Ri =

4 / (11+TFi)

Total

Float

Duration

Di

Activity






1 2 53 4

40 1 3 6 8

23

1812 19

54 7 9 12 16 20 22

Time

No. of

units

6

2321

29 3185

1

Activity 1:

D= 1 day; R = 1 unit/day; Horizontal projection = n-1 / R = 4/1= 4

Activity 2:

D= 3 days; R = 0.667unit/day; Horizontal projection = 4/0.667= 6

Activity 3:

D= 1 day; R = 1 unit/day; Horizontal projection = 4/1= 4

Activity 4:

D= 4 day; R = 0.5 unit/day; Horizontal projection = 4/0.5= 8

Activity 5:

D= 1 day; R = 1 unit/day; Horizontal projection = 4/1= 4

CM P Repetitive

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