Presentation at the AACE Annual Meeting 2015 on Las Vegas, USA. About how can a Line of Balance schedule be modelled with CPM schedulling softwares.

1. (PS-1862) Modelling Line of Balance Schedules
with Start-Finish Relationships
Ricardo Viana Vargas
Felipe Fernandes Moreira

2. Authors
Ricardo Viana Vargas
ricardo@ricardo-
vargas.com
ricardo-vargas.com
@rvvargas
/in/ricardovargas
+45 4533 7673
Felipe Fernandes Moreira
felipef@gmail.com
/in/felipefmoreira
@ffmot
+55 85 32675722
+55 85 86999108

3. INTRODUCTION
3

4. Project Planning
4
Activity
List
Precedence
Diagram Method Network
Diagram

5. Activities Dependencies
5
PREDECESSOR SUCCESSOR
Logical Relationships
≠
Chronological Relationships

6. Line of Balance Scheduling Method (LBSM)
• Absent from PMBOK (discusses the CPM network
concepts most prominently);
• Technique used at construction industry at Brazil,
Finland and Australia (HENRICH & KOSKELA, 2006);
• Related with Lean Construction and Last Planner
System;
• Surging in recent years: need to go further than just the
critical path;
• Drawback: lack of software support.

7. Line of Balance Scheduling Method
• “Unit of Production x Time” Chart;
• Different from the usual “Activity x Time” Gantt Chart;
• Focus on the workflow;
• Scheduling according to the rate of production;
• Number of working units delivered by a working crew.

8. OBJECTIVES
8

9. Objectives
• Since LBSM lacks software support;
• Propose a method for modelling a Line of Balance with
CPM calculations software;
• Method involves the use of “Start-Finish” logical
relationship.
The main objective of this paper is to propose how to
model a Line of Balance schedule, while the secondary
objective is to investigate the “unexpected results” of
this sort of modelling.

10. LINE OF BALANCE SCHEDULING METHOD
10

11. Line of Balance Scheduling Method
• Scheduling according to the rate of production
• Number of working units delivered by a working
crew
List of Activities

12. Line of Balance Scheduling Method
Schedule using the Gantt chart

13. Line of Balance Scheduling Method
Schedule using the LBSM

14. Line of Balance Scheduling Method
Schedule using the LBSM
Rate of Activities
Production
Angular
Coefficient of
each line
0.25
units/day
0.50
units/day
0.33
units/day

15. Line of Balance Scheduling Method
Balancing the
lines
Make the rate of
production of the
activities to be as
similar as possible
Reduce the
Task 2 “speed”
(make its angular
coefficient smaller)
Reduce its
resources by half –
increase duration
from 2 to 4 days

16. Line of Balance Scheduling Method
Balancing lines to achieve a schedule reduction
0.25
units/day
0.50
units/day
0.33
units/day
Project finishing earlier

17. Line of Balance Scheduling Method
4 lines (4 production units)
12 lines
(3 tasks for 4 floors)

18. Line of Balance Scheduling Method
• Significant reduction of lines
• The bigger the number of repetitions, the bigger
the reduction
• Applicable at all sort of repetitive processes
– Eg.: Construction of 100 km, with 20 tasks for
each kilometer

19. Line of Balance Scheduling Method
• Construction industry: tasks are scheduled
continuously (KENLEY & SEPPÄNEN, 2010)
• Could be scheduled without this restriction
Line of Balance without the continuity of repetition

20. Line of Balance Scheduling Method
0.250
units/day
0.286
units/day
0.267
units/day

21. 3-day reduction
Line Balacing Schedule Reduction
Line Balacing is a “Crashing Method!”
Line of Balance Scheduling Method

22. Breaking the continuity restriction will
increase the total time of resource allocation!
16 days
14 days 15 days
16 days 8 days 12 days
Line of Balance Scheduling Method

23. Line of Balance Scheduling Method
Peculiarity: how to model this schedule?

24. Two proposals
Network Approach
•Envolves CPM network calculations
Linear Scheduling Approach
•Drops the CPM network
calculations

25. NETWORK APPROACH
25

26. The Network Approach
Task 1 on the 4th floor defines the start
date of Task 2 on the 4th floor
The last task offers the time
constraint for the task progression!
Task 2
faster than
Task 1
“FS relations”
Connected at the 4th floor

27. The Network Approach
Network Diagram with the logical relationship between tasks

28. The Network Approach
Can’t use the
“FS” relation
Time constraint is transmitted
“downward” from 4th to 1st floor.
Done with the “SF” relation.

29. The Network Approach
SF relation between the repetitions of Task 2

30. The Network Approach
Connected at
the 1st floor
4th floor is no longer the time constraint for the task progression.
Time constraint move “upwards” using the “FS” relation!

31. The Network Approach
Complete network diagram for the example
Important: PM softwares will show every task as critical

32. The Network Approach
Task 2 on the 2nd, 3rd and 4th floor are not critical!

33. The Network Approach
• “FS” logical relationships + As Late As Possible (ALAP)
Breaks the
continuity
Results in a different schedule! Finishes earlier

34. The Network Approach
• Both “SF” and “FS” + ALAP structures offer viable
options for LBSM modelling;
• “SF”:
– Ensures continuous task progressions;
– No risk related to discontinuity.
• “FS” + ALAP:
– Shorter Project duration;
– Risks related with discontinuity.

35. LINEAR SCHEDULE APPROACH
35

36. The Linear Schedule Approach
• Drops the CPM network calculations;
• Uses the software as a “graphical tool”;
• Focus on the fundamentals: flow of work.

37. The Linear Schedule Approach
• Control by flow? Avoid clashes
Clash = Rupture in the workflow

38. • Modelling lines by chaining tasks and subordinating it to
milestones.
“SF” relationships
“FS” relationships

39. CONCLUSION
39

40. Conclusion
• Line of Balance x Gantt Chart;
• LBSM x CPM network;
• Flow x Critical Path;
• Utilization of “Start-Finish” on scheduling;
• Line of Balance as a CPM network:
– “SF” relationships ensures the task progression
continuity;
– “FS” + ALAP potencially reduces the project duration at
the cost of higher risk;
• CPM software as a “graphical tool”:
– End Milestones: “SF” relationships;
– Start Milestones: “FS” relationships.