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(PS-1862) Modelling Line of Balance Schedules with Start- Finish Relationships Ricardo Viana Vargas Felipe Fernandes Moreira
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(PS-1862) Modelling Line of Balance Schedules with Start-Finish Relationships
Ricardo Viana VargasFelipe Fernandes Moreira
Authors
Ricardo Viana [email protected]@rvvargas/in/ricardovargas+45 4533 7673
Felipe Fernandes [email protected]/in/felipefmoreira@ffmot+55 85 32675722+55 85 86999108
INTRODUCTION
3
Project Planning
4
Activity List Precedence Diagram Method Network Diagram
Activities Dependencies
5
PREDECESSOR
SUCCESSOR
Logical Relationships
≠ Chronological Relationships
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.
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.
OBJECTIVES
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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.
LINE OF BALANCE SCHEDULING METHOD
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Line of Balance Scheduling Method
• Scheduling according to the rate of production• Number of working units delivered by a working
crew
List of Activities
Line of Balance Scheduling Method
Schedule using the Gantt chart
Line of Balance Scheduling Method
Schedule using the LBSM
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
Line of Balance Scheduling Method
Balancing the linesMake 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
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
Line of Balance Scheduling Method
4 lines (4 production units)
12 lines(3 tasks for 4 floors)
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
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
Line of Balance Scheduling Method
0.250 units/day
0.286 units/day
0.267 units/day
3-day reduction
Line Balacing Schedule Reduction
Line Balacing is a “Crashing Method!”
Line of Balance Scheduling Method
Breaking the continuity restriction will increase the total time of resource allocation!
16 days14 days 15 days
16 days 8 days 12 days
Line of Balance Scheduling Method
Line of Balance Scheduling Method
Peculiarity: how to model this schedule?
Two proposals
Network Approach
• Envolves CPM network calculations
Linear Scheduling Approach
• Drops the CPM network calculations
NETWORK APPROACH
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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
The Network Approach
Network Diagram with the logical relationship between tasks
The Network Approach
Can’t use the “FS” relation
Time constraint is transmitted “downward” from 4th to 1st floor.
Done with the “SF” relation.
The Network Approach
SF relation between the repetitions of Task 2
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!
The Network Approach
Complete network diagram for the example
Important: PM softwares will show every task as critical
The Network Approach
Task 2 on the 2nd, 3rd and 4th floor are not critical!
The Network Approach
• “FS” logical relationships + As Late As Possible (ALAP)
Breaks the continuity
Results in a different schedule! Finishes earlier
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.
LINEAR SCHEDULE APPROACH
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The Linear Schedule Approach
• Drops the CPM network calculations;• Uses the software as a “graphical tool”;• Focus on the fundamentals: flow of work.
The Linear Schedule Approach
• Control by flow? Avoid clashes
Clash = Rupture in the workflow
• Modelling lines by chaining tasks and subordinating it to milestones.
“SF” relationships
“FS” relationships
CONCLUSION
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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.
