Repetitive Scheduling and Lean Construction - PowerPoint PPT Presentation

1 / 48
About This Presentation
Title:

Repetitive Scheduling and Lean Construction

Description:

Assistant Professor, Chaoyang University of Technology. Ph.D., University of Michigan, Ann Arbor ... Unit Production Rate (e.g., units/day) = unit duration ... – PowerPoint PPT presentation

Number of Views:523
Avg rating:3.0/5.0
Slides: 49
Provided by: itu95
Category:

less

Transcript and Presenter's Notes

Title: Repetitive Scheduling and Lean Construction


1
Repetitive Scheduling and Lean Construction
  • by
  • I-Tung Yang
  • Assistant Professor, Chaoyang University of
    Technology
  • Ph.D., University of Michigan, Ann Arbor

2
(No Transcript)
3
Presentation Outline
  • What is Lean?
  • Where can Lean Philosophy apply in Construction?
  • Classification of repetitive projects
  • Work continuity (unforced idleness)
  • Limitations of previous techniques
  • Proposed modeling elements and algorithm
  • Repetitive Project Planner (RP2)
  • Case Studies
  • Summary and conclusion
  • Current progress and future extension

4
What is Lean?
  • Production philosophy
  • Craftsmanship Mass Production Lean
    Production
  • Make more faster Make what is needed when
    it is needed
  • Ultimate purpose eliminate waste (no
    value-adding)
  • Many concepts are common sense but require
    implementation.
  • Where is the value? How to map the value-stream?
  • Individual efficiency vs. system efficiency

5
Where can Lean Philosophy apply in Construction
  • View of planning units
  • Discrete activities vs. Continuous flow
  • In-process quality control (Andon)
  • Result-focused vs. Process-focused
  • Benchmarking
  • To manage, you have to measure your
    performance.
  • Employee participation
  • Centralization vs. Decentralization
  • Process transparency
  • Visual impact of scheduling

6
Where can Lean Philosophy apply in Construction
(Continued)
  • Supply chain management
  • Long-term, strategic alliance
  • Just-in-time delivery (Kanban)
  • Increase production reliability
  • What can you do instead of What should you do
  • Lookahead scheduling
  • Shield downstream activities from uncertainty
  • Pull/Push scheduling
  • Upstream activities push downstream activities
  • Downstream activities pull upstream activities

7
Some References
  • Koskela, L. (1992). Application of the New
    Production Philosophy to Construction. Technical
    Report 72. Department of Civil Engineering,
    Stanford University.
  • Shingo, S. (1988). Non-stock production.
    Productivity Press, Cambridge, Ma. 454 pp.
  • Womack, J. P., Jones, D. T. (1996). Lean
    Thinking. Simon Schuster, New York. 350 pp.
  • Journal of Construction Research (2002). Special
    Issue Lean Construction. Vol. 3, No. 1. 192pp.
  • International Group of Lean Construction
    (IGLC)http//cic.vtt.fi/lean/

8
Classification of Repetitive Projects
9
Unforced Idleness
  • Cause improper scheduling
  • Problems
  • unproductive waiting
  • comeback delay
  • relocation cost
  • work discontinuity
  • morale impact

10
State of the Art (I)
  • CPM and PERT
  • Too big for what it does
  • Cannot eliminate unforced idleness

11
State of the Art (II)
  • LOB and its variations
  • Graphical, production diagrams, manual
  • Discrete vs. Continuous
  • Typical impractical assumptions
  • Activities need to be performed in all units
  • Production rates and work quantities are
    identical in all units

12
State of the Art (III)
  • Mathematical Optimization Models
  • Linear programming, Dynamic programming, Integer
    Programming
  • Additional limiting assumptions
  • activities are in series (one predecessor and one
    successor)
  • activities follow the same direction
  • Minimization of cost made the model complex
  • Other optimization tools neural networks,
    genetic algorithm

13
State of the Art (IV)
  • Simulation Techniques
  • Variability in production rates
  • Resource interaction
  • By themselves do not solve the problem of
    unforced idleness

14
Limitations of Previous Scheduling Models
  • Unrealistic assumptions
  • No computational algorithm to generate schedules
  • No distinction between units and locations
  • Focus on activities only (not links)
  • Cannot answer Through what kinds of links are
    activities controlled by their predecessors?

15
Realistic Repetitive Scheduling Model
  • Same crew may work in multiple activities
  • One activity may employ multiple crews
  • Varied production rates, work quantities
  • Activities have multiple predecessors
  • Activities may skip units
  • Custom progress direction and work sequence
  • Ability to specify space buffer or time buffer
    between activities
  • Activities occupy entire areas (blocks)
  • Activities occur at locations (bars)

16
Objectives
  • Realistic
  • Necessary modeling elements (activity and link
    types)
  • Universal
  • Schedule both discrete and continuous projects
  • Practical
  • Easily understood graphical schedules
    communication
  • Computational algorithm to automatically generate
    schedules (Repetitive Scheduling Method, RSM)

17
Units vs. LocationsDiscrete vs. Continuous
18
Modeling Elements (I) Activities
  • Activity types
  • Line
  • Block (e.g., excavation, foundation)
  • Bar (e.g., culverts, bridges)

Time
Units
Locations
Time
19
Production Line (I)
  • Production rate (slope)
  • Resource Production Rate (e.g., cubic yards/day)
  • Unit Production Rate (e.g., units/day) gt unit
    duration
  • Start and finish units (locations)
  • Desirable work interruption between units

20
Blocks and Bars
Finish Time
Finish Time
Start Time
Start Time
Start Location
Finish Location
Location
21
Classification of Links
  • What are the types of activities (Line, Block,
    and Bar)?
  • What does the link represent (Tech., Resource,
    Continuity)?
  • What is the measure of the buffer (time versus
    distance)?
  • Where does the link connect?
  • Different unit of the same activity (implied in
    the algorithm)
  • Same unit of different activities
  • Different unit of different activities
  • Is the project continuous or discrete (units
    versus locations)?
  • Which time value does the link connect
    (start/finish)?

22
Modeling Elements (II) Links
23
Time-buffer versus Distance-buffer
24
Global versus Local Time-Controlled
25
Continuity Relationship
  • Pulling Effect

26
Cyclic Links
27
Computational Algorithm (Stage 1) Simple View
28
Computational Algorithm (Stage 2)Pull
Predecessor to Maintain Continuity
  • At most one continuity predecessor
  • Continuity predecessor set
  • Steps (backward calculation)
  • Check for cyclic links if yes, skip the activity
  • Pull continuity predecessor (h)
  • Pull successors of h (re-do forward calculation)

29
Pulling Process
30
Repetitive Project Planner (RP2)
  • 32-bit Window-based program
  • Implement the computational algorithm
  • Validation tool
  • Can it model realistic situations?
  • How long it takes to generate graphical schedules
  • Are the results reasonable?
  • Tested in real-life projects and for educational
    purpose

31
RP2 (I) Main Window
32
RP2 (II) Unit/Location Window
33
RP2 (III) Relationship Window
34
RP2 Output Graphical Schedule (.jpg or .ps)
35
RP2 Output Tabular Report (.xls)
36
Case (I) Pipeline Project
37
Case (I) Pipeline Project
2 Painters
4 Painters
38
Case (II) Highway Rehabilitation
  • 8 km, two-lanes
  • East- and West-bound

39
Case (II) Highway Rehabilitation
  • Major repeating activities
  • Patch Work
  • Dowel bar Retrofit
  • Diamond Grinding
  • Asphalt
  • Other activities
  • Traffic Control
  • Pavement Painting
  • Shoulder Corrugation

40
Case (II) Highway Rehabilitation
41
Case (III) Four-Story Apartments
42
Case (III) Four-Story Apartments
  • Floor plan
  • Special work sequence (superstructure)

43
Case (III) Four-Story Apartments
  • Interior Activities

44
Case (III) Four-Story Apartments
45
Summary and Conclusion
  • Realistic
  • - Necessary modeling elements
  • Universal
  • - Schedule both discrete and continuous projects
  • Practical
  • - Easily understood graphical schedules
  • - Automated generation of schedules

46
Current Progress and Future Extension
  • Being able to identify critical activities and
    controlling sequence
  • Field experiments of RP2
  • Cost-loading feature
  • Input for further optimization (buffer time,
    resource combinations, etc.)
  • Input for stochastic sensitivity analysis
  • Customized grid lines and text fonts

47
Critical Activities and Controlling Sequence
48
Questions and Comments?
Write a Comment
User Comments (0)
About PowerShow.com