Policy analysis for improving performance of a construction project by system dynamics modeling

POLICY ANALYSIS FOR IMPROVING PERFORMANCE OF A CONSTRUCTION PROJECT BY SYSTEM DYNAMICS MODELING by Nguyen Duy Long A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering Examination Committee Prof Stephen O Ogunlana (Chairman) Dr Bonaventura H W Hadikusumo Dr Truong Quang Nationality Previous Degree Vietnamese Bachelor of Engineering in Civil Engineering Hochiminh City University of Technology Hochiminh City, Vietnam Scholarship Donor Asian Development Bank – Japan Scholarship Program (ADB-JSP) Asian Institute of Technology School of Civil Engineering Thailand April 2003 ii ACKNOWLEDGMENTS Many institutions and persons have contributed to the work that culminates in this thesis My graduate study seemed impossible if I had not received a scholarship from donors Therefore, I would firstly like to thank Asian Institute of Technology (AIT) and Asian Development Bank (ADB) for granting me the scholarship To all the faculties: Professor Ogunlana, Dr Chotchai, Dr Suthi, Dr Hadikusumo, and Professor Brockman, I would like to greatly appreciate their lectures and their respectable profundities from which I have luckily learned during my study life in AIT My special thanks extended to Dr Xu Honggang who has been working for Chongshan University (China) and used to be an AIT’s adjunct faculty and taught me sound fundamentals of system dynamics My work on my thesis and the research which preceded it benefited from the excellent tutelage and guidance of Professor Ogunlana and the valuable advice and extensive helps of the other professors in my examination committee, Dr Truong Quang and Dr Hadikusumo My special thanks also go to project managers and the rest of the Hai Van Pass Tunnel project team and practitioners who helped my data collection for the research Next, I would like to thank my professors, senior lecturers and colleagues in Hochiminh City University of Technology for their admirable suggestions and continuous supports I would like to thank all my friends in Construction Management 2001 batch and in AIT for the wonderful time and unforgettable moments that we had been studying and sharing together In addition, I am very grateful for extensive efforts and timely helps of the staffs in the School of Civil Engineering and AIT I owe thanks to those who have helped me maintain a life within which to work during my time at AIT Primary among them are my family who created and kept a home for me to come home to Finally, thanks are due to my sweetheart whom I am separated from only by space iii ABSTRACT Although many studies have been undertaken on factors influencing delays, cost overruns, productivity and safety performance, etc and problems in specific types of projects, these studies seldom discuss common and general problems of construction projects Thus, comprehensive studies on these problems and respective solutions are essential The first part of the research is to gain insight into problems and success factors pertinent to large construction projects in Vietnam The research identifies components mainly responsible for the problems as (1) incompetent designers/contractors, (2) poor estimation and change management, (3) social and technological issues, (4) poor site issues, and (5) improper techniques and tools The components for the success of the large construction projects are (1) comfort, (2) competence, (3) commitment, and (4) communication The second and major part of the research is concerned with understanding and use of project dynamics in order to achieve successful management of large construction projects in today’s ever-evolving business environment This research investigates the impacts of dynamic project structure on performance of a road tunnel project with a focus on the influences of resource reallocation in terms of resource quantity and characteristics, overtime reduction and material incentives An applicable simulation model of a large construction project was built using system dynamics methodology The model was calibrated to a road tunnel project to investigate its dynamic problems and to formulate and evaluate practical policies to improve its performance In order to considerably improve performance and to be able to adapt to different scenarios, six integrated policies combining the individual policies having the most potentials were evaluated The result reveals that reasonable increases of manpower and equipment, material incentives and/or one or two of them combined with no-overtime are the most effective policies for the case study project iv TABLE OF CONTENTS Chapter Title Page Title Page Acknowledgments Abstract Table of Contents List of Figures List of Tables i ii iii iv ix xi INTRODUCTION 1.1 Background 1.2 Problem Statement 1.3 Objectives 1.4 Scope of Work 1.5 Expected Contribution 1 3 LITERATURE REVIEW 2.1 General 2.2 Characteristics of Construction Industry 2.3 Construction Management 2.3.1 Important Elements of Construction Management 2.3.2 Multiple Project Objectives and Their Trade-Off 2.3.3 Characteristics of Traditional Approaches 2.3.4 Factors Affecting Project Performance 2.3.5 Causes and Costs of Rework 2.3.6 Problems of Construction Projects 2.3.7 Success Factors for Construction Projects 2.4 Applications of System Dynamics in Management 2.4.1 The Roles of System Dynamics 2.4.2 New Paradigms for Complex Projects 2.4.3 System Dynamics in Project Management 2.4.4 System Dynamics in Construction Management 2.5 Summary 5 5 6 10 12 12 12 13 14 16 18 METHODOLOGY 3.1 Introduction 3.2 Principles of System Dynamics Modeling 3.3 System Dynamics Modeling Process 3.4 Study Methodology 3.4.1 Questionnaire Survey 3.4.2 System Dynamics Modeling 3.4.2.1 Problem Articulation 3.4.2.2 Feedback Structures as Dynamic Hypotheses 3.4.2.3 Formulating a Simulation Model 3.4.2.4 Model Testing 3.4.2.5 Policy Design and Evaluation 3.5 The Major Elements of System Dynamics 3.5.1 Feedback 19 19 19 19 20 21 22 22 22 23 23 24 24 24 v Chapter Title Page 3.5.2 Time Delays 3.5.3 Stocks and Flows 3.5.4 Nonlinearity 3.6 Tools for the Research 24 25 25 25 PROBLEMS AND SUCCESS FACTORS 4.1 Introduction 4.2 Respondent’s Characteristics 4.3 Achievements of Project Objectives 4.4 Problems of Large Construction Projects 4.4.1 Rankings of Problems’ Occurrence and Influence 4.4.2 Factor Analysis of Problems’ Occurrence 4.5 Success Factors for Large Construction Projects 4.5.1 Analysis and Ranking of Success Factors 4.5.2 Factor Analysis of the Success Factors 4.5.3 Discussion of Factor Analysis for the Success Factors 4.6 Summary of Problems and Success Factors 26 26 26 27 27 27 29 32 33 34 35 36 PROBLEM ARTICULATION AND FEEDBACK STRUCTURES 5.1 Introduction 5.2 Hai Van Pass Tunnel Project 5.2.1 Project Description 5.2.2 Tunnel Construction Methods 5.2.3 Problems Encountered 5.3 Reference Modes 5.3.1 Project Schedule 5.3.2 Budget Status 5.3.3 Quality goal 5.4 Key Feedback Structures of Construction Projects 5.4.1 The Structure of Labor 5.4.2 The Structure of Equipment 5.4.3 The Structure of Material 5.4.4 The Structure of Labor-Equipment Interaction 5.4.5 The Structure of Schedule 5.4.6 The Structure of Rework 5.4.7 The Structure of Safety 5.4.8 The Structure of Quality 5.5 Summary 38 38 38 38 39 40 40 40 41 41 42 42 43 43 44 44 45 46 46 47 MODEL DESCRIPTION 6.1 Introduction 6.2 Model Boundary 6.3 Model Structure 6.3.1 Model Subsystems 6.3.2 Scope Subsystem 6.3.3 Progress and Rework Subsystem 6.3.4 Resources Subsystem 6.3.4.1 Manpower Sector 48 48 48 49 49 50 51 52 52 vi Chapter Title Page 6.3.4.2 Major Equipment Sector 6.3.4.3 Supportive Equipment Sector 6.3.4.4 Material Sector 6.3.4.5 Skills sector 6.3.5 Performance Subsystem 6.3.5.1 Labor Productivity Sector 6.3.5.2 Equipment Productivity Sector 6.3.5.3 Experience Sector 6.3.5.4 The Safety Sector 6.3.5.5 The Quality of Practice Sector 6.3.5.6 Work-month Sector 6.3.5.7 The Supervision Sector 6.3.6 Cost Breakdown Subsystem 6.3.6.1 Material Cost Sector 6.3.6.2 Labor Cost Sector 6.3.6.3 Equipment Cost Sector 6.3.7 Objectives Control Subsystem 6.3.7.1 Schedule Control Sector 6.3.7.2 Cost Control Sector 6.3.7.3 Quality Control Sector 6.4 Model References 6.5 Model Description Summary 54 55 56 57 58 58 59 60 61 62 62 63 64 64 65 65 66 66 67 68 69 70 MODEL TESTING 7.1 General 7.2 Model Behavior 7.2.1 Introduction 7.2.2 Work and Rework 7.2.3 Resource Allocation and Progress 7.2.4 Labor Productivity 7.2.5 Experience and Safety 7.2.6 Scheduling and Work-month 7.2.7 Project Expenses 7.2.8 Summary of Model Behavior 7.3 Model Testing 7.3.1 Introduction 7.3.2 Boundary Adequacy Tests 7.3.3 Structure Assessment Tests 7.3.4 Dimensional Consistency 7.3.5 Parameter Assessment 7.3.6 Extreme Condition Tests 7.3.7 Integration Error Tests 7.3.8 Behavior Reproduction Tests 7.3.9 Sensitivity Analysis Tests 7.3.10 Model testing summary 71 71 71 71 71 72 74 75 77 78 79 79 79 79 79 80 80 80 80 82 83 84 POLICY ANAYSIS 8.1 Introduction 85 85 vii Chapter Title Page 8.2 Implications of the Base Run and the Project Practice 8.2.1 Simulated and Actual Progresses 8.2.2 The Tunneling Method 8.2.3 The Project Control Mechanism 8.2.4 Employment and Workers’ Morale 8.2.5 Equipment Investment 8.3 Policy Alternatives 8.3.1 Adjustments of the Proportion of Skilled and Unskilled Workers 8.3.2 Adjustments of the Proportion of Management Team and Workforce 8.3.3 Reallocation of the Resources 8.3.4 Reduction of Overtime and Worker’s Fatigue 8.3.5 Pay Increases as Material Incentives 8.3.6 Summary of the Policy Alternatives 8.4 Policy Evaluation 8.4.1 Evaluation of Separate Policies 8.4.1.1 Skills Adjustment Policies 8.4.1.2 Management Team Adjustment Policies 8.4.1.3 Resource Reallocation Policies 8.4.1.4 Overtime Reduction and Material Incentives Policies 8.4.2 Evaluation for Integrated Policies 8.5 Policy Analysis Summary 85 85 85 85 86 86 86 86 CONCLUSIONS AND RECOMMENDATIONS 9.1 General Conclusions 9.2 Problems of Large Construction Projects 9.3 Success Factors of Large Construction Projects 9.4 Importance of the Dynamics of Construction Projects 9.5 Major Findings and Discussion about ASM 9.5.1 The Trustworthiness of ASM 9.5.2 The Contribution of Equipment to Project Progress 9.5.3 The Dynamics of Manpower and Equipment Interaction 9.5.4 Feedback, Delays and Nonlinear Relationships in Construction Projects 9.5.5 Policies for Improving Performance of the Case Study Project 9.6 Contributions 9.6.1 Lessons Learned for Vietnam Construction Industry 9.6.2 A New Promising Tool for Construction Practitioners 9.7 Limitations of the Research 9.7.1 Limitations of the Survey 9.7.2 Limitations of the Dynamic Simulation Model 9.8 Recommendations for Future Research 97 97 97 97 98 99 99 99 99 100 References Appendix A 104 110 Questionnaire viii 87 87 89 89 90 91 91 91 92 93 94 95 96 100 101 101 101 102 102 102 102 Chapter Title Appendix B Appendix C Appendix D Appendix E Appendix F Appendix G Appendix H Appendix I Appendix K Page Structured Interview 114 Ranking of Problems’ Occurrence 125 Ranking of Problems’ Influence 127 Model Equations 129 Sensitivity Analysis Results of Selected Parameters 137 Sensitivity Analysis of Selected Nonlinear Relationships 141 Selected Plots of Sensitivity Analysis 143 Project Schedule and Progress 145 Model Variables 146 ix LIST OF FIGURES Figure No Title Page 1.1 2.1 2.2 2.3 2.4 2.5 3.1 3.2 3.3 3.4 3.5 4.1 4.2 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 6.18 6.19 6.20 Management style vs uncertainty profile Factor-resource model Framework for determining Critical Success/Failure factors Fishbone diagram for identifying causes of rework Project complexity Overview of the SYDPIM process logic Iterative cycle of modeling process Flowchart of research methodology Sixteen steps involved in the construction of reference mode Positive feedback versus negative feedback Stock and flow diagramming notation Scree plot of factor analysis of problems’ occurrence Scree plot of factor analysis of success factors Drill and blast method Hydraulic hammering method The dynamics of the project showing schedule delays The dynamics of the project showing cost overruns The dynamics of the project showing quality erosion The labor structure The equipment structure The material structure The labor-equipment interaction structure The schedule structure The rework structure The safety structure The quality structure Model breakdown structure Scope and scope change sectors Progress and rework sectors Manpower sector Major equipment sector Supportive equipment sector Supportive equipment sector Skills sector Labor productivity sector Equipment productivity sector Experience sector Safety sector Quality of practice sector Work-month sector Supervision sector Material cost sector Labor cost sector Equipment cost sector Schedule control sector Cost control sector x 10 13 15 19 21 23 24 25 30 34 39 39 40 41 42 42 43 44 44 45 45 46 47 50 50 51 52 54 55 56 57 58 59 60 61 62 62 64 64 65 66 66 68 Figure No Title Page 6.21 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 7.18 7.19 7.20 7.21 8.1 8.2 8.3 8.4 H.1 H.2 H.3 H.4 H.5 H.6 H.7 H.8 H.9 H.10 H.11 H.12 H.13 H.14 H.15 H.15 Quality control sector Work and rework Work quality Project progress Manpower input Equipment input Material input Material delivery Labor productivity Cumulative experience and experience index Accident frequency and accident index Scheduling and schedule pressure Average work-month and overtime index Project cash flow Project costing and budget status Response to no purchase Response to no employment Sensitivity to time step Work accomplished – simulated output and historical data Unskilled workers – simulated output and historical data Skilled workers – simulated output and historical data Management team – simulated output and historical data Key feedbacks in response to skills adjustment Key feedbacks in response to management team adjustment Progress under policy P3b Progress under policy P3c Experience effect on labor productivity Experience effect on equipment productivity Experience effect on rework Schedule pressure effect on work-month Schedule pressure effect on labor productivity Schedule pressure effect on equipment productivity Schedule pressure effect on rework Fatigue effect on labor productivity Fatigue effect on equipment productivity Fatigue effect on rework Skills effect on rework Skills effect on labor productivity Supervision effect on rework Supervision effect on productivity Accidents effect on labor productivity Accidents effect on equipment productivity xi 69 72 72 73 73 74 74 75 75 76 76 77 77 78 78 81 81 82 82 82 83 83 92 93 94 94 143 143 143 143 143 143 143 143 144 144 144 144 144 144 144 144 (189) (190) (191) (192) (193) (194) (195) (196) (197) (198) (199) (200) (201) (202) (203) (204) (205) (206) (207) (208) (209) (210) (211) (212) (213) (214) (215) (216) (217) (218) (219) rework discovery rate = (Undiscovered rework/time to discover defects)*discovered rework probability Units: tasks/Month rework material cost = rework material rate*material unit cost Units: $/Month rework material rate = progress rate*material fraction*(1-quality of practice)*discovered rework probability Units: units/Month SAVEPER = Units: Month [0,?] The frequency with which output is stored schedule pressure = (scheduled completion date/Project deadline) Units: Dmnl scheduled completion date = Time + time estimated required Units: months scope change rate = avg change fraction*initial project scope Units: tasks/Month Skilled workers = INTEG (change in sw+onsite training rate-sw turnover rate,initial sw) Units: persons skills effect on accident = WITH LOOKUP (skills fraction,([(0,0.75)-(1,1.3)],(0,1.3),(0.1,1.25), (0.2,1.2),(0.3,1.15),(0.4,1.1),(0.5,1.05),(0.6,1),(0.7,0.95),(0.8,0.9),(0.9,0.83),(1,0.75) )) Units: Dmnl skills effect on labor prodty = WITH LOOKUP (skills fraction,([(0,0.5)-(1,1.3)],(0,0.5),(0.1,0.6), (0.2,0.7),(0.3,0.78),(0.4,0.85),(0.5,0.93),(0.6,1),(0.7,1.09),(0.8,1.18),(0.9,1.25),(1,1.3) ))Units: Dmnl skills effect on rework = WITH LOOKUP (skills fraction,([(0,0.75)-(1,2)],(0,2),(0.1,1.7), (0.2,1.5),(0.3,1.32),(0.4,1.18),(0.5,1.08),(0.6,1),(0.7,0.9),(0.8,0.84),(0.9,0.78),(1,0.75) ))Units: Dmnl skills effect on waste = WITH LOOKUP (skills fraction,([(0,0.6)-(1,2)],(0,2),(0.1,1.75),(0.2,1.55), (0.3,1.38),(0.4,1.24),(0.5,1.11),(0.6,1),(0.7,0.87),(0.8,0.75),(0.9,0.67),(1,0.6) )) Units: Dmnl skills fraction = Skilled workers/(Skilled workers + Unskilled workers) Units: Dmnl sp effect on accident = WITH LOOKUP (schedule pressure,([(0.5,0.9)-(2,1.5)],(0.5,0.9),(0.75,0.93), (1,1),(1.25,1.1),(1.5,1.21),(1.75,1.35),(2,1.5) )) Units: Dmnl sp effect on equip prodty = WITH LOOKUP (schedule pressure,([(0.5,0.95)-(2,1.15)],(0.5,0.95), (0.75,0.97),(1,1),(1.25,1.06),(1.5,1.11),(1.75,1.14),(2,1.15) )) Units: Dmnl sp effect on labor prodty = WITH LOOKUP (schedule pressure,([(0.5,0.9)-(2,1.25)],(0.5,0.9), (0.75,0.92),(1,1),(1.25,1.1),(1.5,1.18),(1.75,1.23),(2,1.25) )) Units: Dmnl sp effect on rework = WITH LOOKUP (schedule pressure,([(0.5,0.7)-(2,1.5)],(0.5,1),(0.75,1), (1,1),(1.25,1.05),(1.5,1.15),(1.75,1.3),(2,1.5) )) Units: Dmnl sp effect on waste = WITH LOOKUP (schedule pressure,([(0.5,0.9)-(2,1.5)],(0.5,0.9),(0.75,0.93), (1,1),(1.25,1.1),(1.5,1.21),(1.75,1.35),(2,1.5) )) Units: Dmnl sp effect on workmonth = WITH LOOKUP (schedule pressure,([(0.5,0.9)-(2,1.5)],(0.5,0.9), (0.75,0.92),(1,1),(1.25,1.2),(1.5,1.36),(1.75,1.46),(2,1.5) )) Units: Dmnl stock coverage time = 0.6666 Units: months stock effect on equip sought = WITH LOOKUP (Material in stock/stock goal,([(0,0)-(0.5,1)],(0,0), (0.05,0.05),(0.1,0.1),(0.15,0.15),(0.2,0.25),(0.25,0.5),(0.3,0.85),(0.35,0.95),(0.4,1),(0.45,1),(0.5,1) )) Units: Dmnl stock effect on wf sought = WITH LOOKUP (Material in stock/stock goal,([(0,0)-(0.5,1)],(0,0), (0.05,0.05),(0.1,0.1),(0.15,0.15),(0.2,0.25),(0.25,0.5),(0.3,0.85),(0.35,0.95),(0.4,1),(0.45,1),(0.5,1) )) Units: Dmnl stock goal = reported material use rate*stock coverage time Units: units stock goal difference = MAX(stock goal-Material in stock,0) Units: units straight time = workforce*normal wokmonth Units: persons*hour/Month straight time cost = straight time*((Management team*mt wage + Skilled workers*sw wage + Unskilled workers*uw wage)/(Management team + Skilled workers + Unskilled workers)) Units: $/Month sup equip adjustment time = Units: months sup equip de unit = 250 Units: $/Month/unit sup equip effect on labor progress = WITH LOOKUP (Supportive equipment/normal sub equip, ([(0.4,0.6)-(2,1.2)],(0.4,0.6),(0.6,0.75),(0.8,0.89),(1,1),(1.2,1.06),(1.4,1.11),(1.6,1.15), (1.8,1.18),(2,1.2) )) Units: Dmnl sup equip sought = indicated sup equip*bg status effect on sup equip sought Units: units supervision effect on accident = WITH LOOKUP (supervision index,([(0.1,0)-(2.5,2)],(0.1,2), (0.4,1.6),(0.7,1.3),(1,1),(1.3,0.8),(1.6,0.6),(1.9,0.5),(2.2,0.4),(2.5,0.3) )) Units: Dmnl 135 (220) (221) (222) (223) (224) (225) (226) (227) (228) (229) (230) (231) (232) (233) (234) (235) (236) (237) (238) (239) (240) (241) (242) (243) (244) (245) (246) (247) (248) (249) supervision effect on prodty = WITH LOOKUP (supervision index,([(0,0.6)-(2.5,1.2)],(0.1,0.6), (0.4,0.75),(0.7,0.88),(1,1),(1.3,1.06),(1.6,1.11),(1.9,1.15),(2.2,1.18),(2.5,1.2) )) Units: Dmnl supervision effect on rework = WITH LOOKUP (supervision index,([(0.1,0.5)-(2.5,1.3)],(0.1,1.3), (0.4,1.2),(0.7,1.1),(1,1),(1.3,0.9),(1.6,0.8),(1.9,0.7),(2.2,0.6),(2.5,0.5) )) Units: Dmnl supervision effect on waste = WITH LOOKUP (supervision index,([(0,0.5)-(2.5,3)],(0.1,3),(0.4,2.1), (0.7,1.5),(1,1),(1.3,0.82),(1.6,0.72),(1.9,0.63),(2.2,0.56),(2.5,0.5) )) Units: Dmnl supervision index = ((Management team/workforce)/normal mgt fraction) Units: Dmnl Supportive equipment = INTEG (change in sup equip,initial sup equip) Units: units sw adjustment time= 0.5 Units: Month sw turnover rate = Skilled workers*normal sw turnover fraction*fatigue effect on turnover Units: persons/Month sw wage = 0.75 Units: $/person/hour "sw/uw fraction" = "normal sw/uw fraction"*"qual gap effect on sw/uw" Units: Dmnl time estimated required = Work remaining/expected progress rate Units: months time remain effect on invest equip = WITH LOOKUP (time remaining,([(0,0.5)-(40,2)],(0,2), (4,1.75),(8,1.5),(12,1.25),(16,1.15),(20,1.05),(24,1),(28,1),(32,1),(36,1),(40,1) )) Units: Dmnl time remaining = MAX(Project deadline-Time, time remaining) Units: months TIME STEP = 0.01 Units: Month [0,?] The time step for the simulation time to discover defects = WITH LOOKUP (fraction perceived completed,([(0,0)-(1,3)],(0,1), (0.2,1),(0.4,1),(0.6,0.75),(0.8,0.5),(1,0.25) )) Units: months training fraction = 0.1 Units: Dmnl Undiscovered rework = INTEG (progress rate*(1-quality of practice)-rework discovery rate,0) Units: tasks Unskilled workers = INTEG (change in uw-onsite training rate-uw tunover rate, initial uw) Units: persons uw adjustment time = 0.5 Units: Month uw tunover rate = Unskilled workers*normal uw turnover fraction*fatigue effect on turnover Units: persons/Month uw wage = 0.42 Units: $/person/hour waste material cost = waste material rate*material unit cost Units: $/Month waste material rate = normal waste fraction*progress rate*material fraction*exp effect on waste *skills effect on waste*sp effect on waste*supervision effect on waste Units: units/Month WF sought = MIN(indicated WF*bg status effect on wf sought*stock effect on wf sought* manpower resource leveling, max workforce by space constraints) Units: persons Work accomplished = INTEG (progress rate-rework discovery rate,0) Units: tasks Work remaining = INTEG (-progress rate + rework discovery rate + scope change rate,initial project scope) Units: tasks workers sought = WF sought*(1-mgt fraction) Units: persons workforce = Unskilled workers + Skilled workers + Management team Units: persons workmonth = MIN(normal wokmonth*sp effect on workmonth, max workmonth) Units: hours/Month workmonth avg time = Units: months workmonth effect on mtn = WITH LOOKUP (workmonth/normal wokmonth,([(0.9,0.98)-(1.5,1.2)], (0.9,0.98),(1,1),(1.1,1.02),(1.2,1.05),(1.3,1.09),(1.4,1.14),(1.5,1.2) )) Units: Dmnl 136 APPENDIX H SELECTED PLOTS OF SENSITIVITY ANALYSIS Expected labor prodty current labor prodty 0.4 0.4 0.325 0.25 2 0.175 1 3 2 31 3 3 3 3 0.325 0.25 1 31 0.175 0.1 23 12 3 12 2 3 23 1 23 23 12 12 23 12 123 0.1 12 16 20 Expected labor prodty : Baserun Expected labor prodty : Test1 Expected labor prodty : Test23 24 28 32 Time (Month) 2 3 36 40 48 52 tasks/(Month*person) tasks/(Month*person) tasks/(Month*person) 44 12 16 20 24 28 32 Time (Month) 36 40 current labor prodty : Baserun 1 1 1 current labor prodty : Test12 2 2 current labor prodty : Test2 3 3 3 Figure H.1 exp effect on labor prodty 44 48 52 tasks/(Month*person) tasks/(Month*person) tasks/(Month*person) Figure H.5 sp effect on labor prodty Reported equip prodty real equip prodty 10 10 8.5 2 2 5.5 3 3 1 3 1 1 3 3 2 1 3 2 2 2 8.5 23 1 5.5 31 4 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 23 Reported equip prodty : Baserun 1 1 tasks/(Month*unit) Reported equip prodty : Test1 2 2 2 tasks/(Month*unit) Reported equip prodty : Test23 3 3 3 tasks/(Month*unit) 12 12 12 16 20 3 7.5 3 12 12 12 12 123 31 23 3 2 3 36 3 44 48 52 tasks/(Month*unit) tasks/(Month*unit) tasks/(Month*unit) 40 Figure H.6 sp effect on equip prodty 450 12 23 23 123 150 12 0 16 20 24 28 32 Time (Month) 36 40 44 48 52 23 Undiscovered rework : Bas erun1 1 1 1 1 tasks Undiscovered rework : Test1 2 2 2 2 tasks Undiscovered rework : Test2 3 3 3 3 tasks 23 23 23 12 31 16 31 20 31 31 2 123 2 300 123 12 2 1 23 2.5 Known rework 2 12 600 12 12 12 24 28 32 Time (Month) Undiscovered rework 10 23 real equip prodty : Baserun real equip prodty : Test1 real equip prodty : Test23 Figure H.2 exp effect on equip prodty 31 31 24 28 32 Time (Month) 31 36 40 31 31 44 48 31 52 Known rework : Baserun 1 1 1 1 1 tasks Known rework : Test12 2 2 2 2 2 tasks Known rework : Test2 3 3 3 3 3 tasks Figure H.3 exp effect on rework Figure H.7 sp effect on rework current labor prodty workforce 0.4 800 700 31 600 2 3 1 23 23 23 23 23 23 23 23 0.325 0.25 3 0.175 500 400 23 3 3 3 3 3 12 3 0.1 23 12 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 12 16 20 24 28 32 Time (Month) 36 current labor prodty : Baserun 1 1 1 current labor prodty : Test12 2 2 current labor prodty : Test2 3 3 3 workforc e : Baserun 1 1 1 1 1 persons workforc e : Tes t1 2 2 2 2 2 persons workforc e : Tes t2 3 3 3 3 3 persons 40 44 48 52 tasks/(Month*person) tasks/(Month*person) tasks/(Month*person) Figure H.8 fatigue effect on labor prodty Figure H.4 sp effect on work-month 143 Reported equip prodty Undiscovered rework 10 10 8.5 2 5.5 23 31 1 1 3 3 2 3 7.5 1 2 2 231 2312 23 31 31 23 12 23 31 23 12 31 23 2.5 12 31 23 12 0 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 Reported equip prodty : Baserun 1 1 tasks/(Month*unit) Reported equip prodty : Test1 2 2 2 tasks/(Month*unit) Reported equip prodty : Test23 3 3 3 tasks/(Month*unit) 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 Undiscovered rework : Bas erun1 1 1 1 1 tasks Undiscovered rework : Test1 2 2 2 2 tasks Undiscovered rework : Test2 3 3 3 3 tasks Figure H.9 fatigue effect on equip prodty Figure H.13 supervision effect on rework Undiscovered rework current equip prodty 10 10 31 12 7.5 31 31 2 3 31 31 231 8.5 231 231 23 1 23 2.5 31 23 5.5 12 23 12 31 23 12 31 31 31 3 23 231 31 4 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 Undiscovered rework : Bas erun1 1 1 1 1 tasks Undiscovered rework : Test1 2 2 2 2 tasks Undiscovered rework : Test2 3 3 3 3 tasks 12 16 20 24 28 32 Time (Month) 36 current equip prodty : Baserun 1 1 1 current equip prodty : Test12 2 2 2 current equip prodty : Test2 3 3 3 Figure H.10 fatigue effect on rework 40 44 48 52 tasks/(units*months ) tasks/(units*months ) tasks/(units*months ) Figure H.14 supervision effect on prodty rework discovery rate real labor prodty 10 0.4 7.5 31 231 2312 23 31 31 12 3 23 31 0.3 23 0.2 1 2.5 31 23 12 31 31 12 3 23 1 31 23 0.1 0 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 rework discovery rate : Baserun1 1 1 1 tasks/Month rework discovery rate : Test1 2 2 2 tasks/Month rework discovery rate : Test23 3 3 3 tasks/Month 12 16 20 24 28 32 Time (Month) 36 real labor prodty : Baserun1 1 1 1 real labor prodty : Test1 2 2 2 real labor prodty : Test2 3 3 3 Figure H.11 skills effect on rework 40 44 48 52 tasks/(Month*person) tasks/(Month*person) tasks/(Month*person) Figure H.15 accident effect on labor prodty real labor prodty Expected equip prodty 0.4 10 0.325 0.25 0.175 31 23 12 31 23 12 31 23 23 12 23 12 23 12 23 12 7.5 123 1 1 23 23 12 23 23 123 12 3 12 3 23 31 3 2.5 0.1 0 12 16 20 24 28 32 Time (Month) 36 real labor prodty : Baserun1 1 1 1 real labor prodty : Test1 2 2 2 real labor prodty : Test2 3 3 3 40 44 48 52 tasks/(Month*person) tasks/(Month*person) tasks/(Month*person) 12 16 20 24 28 32 Time (Month) 36 40 44 48 52 Expected equip prodty : Baserun 1 1 tasks/(Month*unit) Expected equip prodty : Test1 2 2 2 tasks/(Month*unit) Expected equip prodty : Test23 3 3 3 tasks/(Month*unit) Figure H.12 skills effect on labor prodty Figure H.16 accident effect on equip prodty 144 APPENDIX I 145 APPENDIX K MODEL VARIABLES Notes of Model Variables This appendix clarifies and defines variables that are used in the ASM and/or its policy analysis List of Variables acc effect on equip prodty: a nonlinear relationship which indicates the effect of accident frequency on equipment productivity, dimensionless acc effect on labor prodty: a nonlinear relationship which indicates the effect of accident frequency on labor productivity, dimensionless acc effect on overhead: a nonlinear relationship which indicates the effect of accident frequency on overhead costs, dimensionless accident generation rate: the rate indicates accident frequency, events per month accident index: the ratio of current accident frequency and normal or historical accident frequency, dimensionless adjust expect equip prodty time: the time for contractors to adjust their expected equipment productivity to current actual equipment productivity, months adjust expect labor prodty time: the time for contractors to adjust their expected labor productivity to current actual labor productivity, months adjust order time: a time for contractors to adjust and order materials, months avg change fraction: the average proportion of scope changes and initial project scope per month, per month avg cost: the actual cost per task at a certain time, $ per task avg memb exp: the average experience level of team members, experiences per person avg new memb exp: the amount of useful experience which each new team member brings to the project, experiences per person avg report equip prodty time: the time for management team to prepare and complete equipment productivity reports, months Avg workmonth: the average number of hours worked in a month by employees, hours per month avg workmonth change: the change in the average workweek, hours per month per month bg status effect on major equip sought: a nonlinear relationship which indicates the effect of budget status on seeking major equipment, dimensionless bg status effect on sup equip sought: a nonlinear relationship which indicates the effect of budget status on seeking supportive equipment, dimensionless bg status effect on wf sought: a nonlinear relationship which indicates the effect of budget status on seeking manpower, dimensionless budget status: the proportion of cost variance and contract price to date, dimensionless c/o effect on deadline: the ratio indicates the effect of scope change (c/o = change orders) on project deadline, dimensionless change in deadline: the approved time extension due to change orders and contractors’ claims, months per month 146 change in expect equip prodty: the time for contractors to adjust their expected equipment productivity to the current equipment productivity, tasks per unit per month per month change in expected labor prodty: the time for contractors to adjust their expected labor productivity to the current labor productivity, tasks per unit per month per month change in investing equip: the mobilization of invested major equipment on or off construction site, units per month change in mt: the moving of management team on or of the construction site, persons per month change in report equip prodty: the increase or decrease in the reported equipment productivity based on actual equipment productivity, tasks per unit per month per month change in report labor prodty: the increase or decrease in the reported labor productivity based on actual labor productivity, tasks per unit per month per month change in sup equip: the mobilization of supportive equipment on or off construction site, units per month change in sw: the moving of skilled workers on or of the construction site, persons per month change in uw: the moving of unskilled workers on or of the construction site, persons per month change in workforce: the moving of manpower on or of the construction site, persons per month change quality goal: the movement of the quality for the project toward the actual quality experienced in the project, per month contract price to date: the contract price including additional costs due to change orders, $ cost expend: total costs for both direct and indirect costs per month, $ per Month cost variance: the difference between contract price and project updated and forecasted costs, $ Cum scope changes: the sum of scope changes, tasks Cumulative accidents: the sum of accidents occurring in construction site, events Cumulative experience: the sum of experiences during project progress, experiences current equip prodty: the instantaneous equipment productivity, tasks per months per unit current known quality: the percent of total tasks completed initially which are believed to not be flawed, dimensionless current labor prodty: the instantaneous labor productivity, tasks per months per person current project scope: the project scope including scope changes, tasks delivery rate: the rate at which materials are delivered to construction site, units per month depreciation cost: the depreciation costs of equipment and plant which are charged in project costs per month, $ per month discovered rework probability: the percent of flawed work that is discovered by quality assurance, dimensionless equip breakdown rate: the faction of equipment broken down per month, units per month 147 equip leasing rate: the rate at which the major equipment is leased, units per month equip repaired rate: the rate at which major equipment is repaired and returned to operations, units per month equip resource leveling: a nonlinear relationship which levels major equipment input, dimensionless equip retire rate: the rate at which equipment retires due to out of expectancy, units per month equipment cost: the total of depreciation, operation and maintenance costs of equipment and plant per month, $ per month equipment sought: the number of major equipment which is sought to fulfill the project progress, units exp effect on accident: a nonlinear relationship which indicates the effect of experience on accident frequency, dimensionless exp effect on equip breakdown: a nonlinear relationship which indicates the effect of experience on major equipment breakdown, dimensionless exp effect on equip prodty: a nonlinear relationship which indicates the effect of experience on equipment productivity, dimensionless exp effect on equip retire: a nonlinear relationship which indicates the effect of experience on equipment retirements, dimensionless exp effect on labor prodty: a nonlinear relationship which indicates the effect of experience on labor productivity, dimensionless exp effect on rework: a nonlinear relationship which indicates the effect of experience on rework, dimensionless exp effect on waste: a nonlinear relationship which indicates the effect of experience on material wastes, dimensionless exp index: the improvement in performance factors due to increased experience This formulation is based upon the learning curve concept The learning curve effect is modeled by increasing the current productivity 20% for every doubling of cumulative experience of the construction project team, dimensionless exp lost: the experience lost due to the departure of experienced employees, experiences per month exp per task: the number of experiences per project tasks, experiences per task Expected equip prodty: the equipment productivity which contractors expect to be experienced based on the reported equipment productivity, tasks per unit per month Expected labor prodty: the labor productivity which contractors expect to be experienced based on the reported labor productivity, tasks per unit per month expected progress rate: the progress which contractors expect to be experienced based on the reported project progress, tasks per month experience change: the increases or decreases of experiences during the construction, experiences per month fatigue effect on accident: a nonlinear relationship which indicates the effect of fatigue on accidents, dimensionless fatigue effect on equip prodty: a nonlinear relationship which indicates the effect of fatigue on equipment productivity, dimensionless 148 fatigue effect on labor prodty: a nonlinear relationship which indicates the effect of fatigue on labor productivity, dimensionless fatigue effect on rework: a nonlinear relationship which indicates the effect of fatigue on rework, dimensionless fatigue effect on turnover: a nonlinear relationship which indicates the effect of fatigue on labor turnover, dimensionless FINAL TIME: the final time for the simulation, default in Vensim, months forecasted cost: the estimated costs of work remaining based on actual costs of worked performed, $ frac complete effect on order: a nonlinear relationship which indicates the effect of completion fraction on material orders, dimensionless fraction perceived completed: the percent of work performed and perceived unflawed work, dimensionless gross manpower: the total manpower available to construction site, based upon workforce and work-month, person*hours per month indicated equip: the number of major equipment needed before adjustments, units indicated sup equip: the number of supportive equipment needed before adjustments, units indicated WF: the number of manpower needed before adjustments, persons initial contract price: the contract price specified in original contract between owners and contractors, $ initial deadline: the duration specified in original contract between owners and contractors, months initial experience: the number of experiences of manpower at project commencement, experiences initial invested major equip: major equipment units invested into a project at project commencement, units initial leased equip: major equipment units leased for a project at project commencement, units initial material in stock: material units delivered into construction site at project commencement, units initial mt: management team members employed for a project at project commencement, persons initial ordered material: material units ordered for a project at project commencement, units initial project scope: the project scope specified in original contract documents, tasks initial quality goal: a proportion of unflawed work and total work done targeted by contractors before project commencement, dimensionless initial sup equip: supportive equipment units mobilized into project site at project commencement, units initial sw: skilled workers employed for a project at project commencement, persons INITIAL TIME: the initial time for the simulation, default in Vensim, months initial uw: unskilled workers employed for a project at project commencement, persons initial workforce: manpower employed for a project at project commencement, persons 149 interest rate: the rate which contractors pay for their use of money to perform projects, per month invested equip fraction: the proportion of invested major equipment and total major equipment on construction site, dimensionless Invested major equipment: major equipment units which currently operate on construction site invt equip adjustment time: the time for contractors to adjust and decide investment of major equipment, months Known rework: the number of tasks performed which are known to be flawed and to require rework labor cost: the total labor costs expended per month, $ per month labor progress rate: the number of tasks performed per month which manpower can contribute, tasks per month learning time: the time for unskilled workers learning and trained on site to become skilled workers, months lease equip time: the time needed for contractors to lease major equipment, months leased equip return rate: the rate at which equipment has to be returned to leasers, units per month leased equip return time: the time specified in lease agreements, months Leased equipment: the major equipment units leased and operating onsite, units liquidated damage rate: the fraction of liquidated damages and contract price specified in a contract if contractors delay a project, per month liquidated damages: the sum of money which is charged by the owners due to nonexcusable delays, $ maintenance cost: the costs for maintaining all equipment units per month, $ per month per unit Major equip in maintenance: major equipment units maintained due to breakdown, units major equip input: the sum of invested and leased major equipment onsite, units major equip progress rate: the number of tasks performed per month which major equipment can contribute, tasks per month Management team: the number of management team members onsite, persons manpower resource leveling: a nonlinear relationship which levels manpower input, dimensionless market predict effect on invest equip: a nonlinear relationship which reflects the effect of market prediction on equipment investment, dimensionless material cost: the costs expended for materials per month, $ per month material fraction: the quantity of materials per task, units per task Material in stock: the quantity of materials onsite, units material inspect time: the time to inspect material prior to being imported to construction site, months material leadtime: the time needed for suppliers manufacturing, preparing and transporting to site, months Material on order: the quantity of materials on the list of material order forms, units material unit cost: the unit price of materials, $ per unit 150 material use rate: the rate at which materials are used during the construction, units per month max equip by space constraints: maximum major equipment units that can operate normally onsite, units max sup equip: maximum supportive equipment units that can operate normally onsite, units max workforce by space constraints: maximum workforce that can work normally onsite, workers max workmonth: maximum number of hours that laborers can work, hours per month mgt fraction: a proportion of management team and total workforce, dimensionless time remaining: minimum time remainders of project progress, month workforce: minimum workforce that can perform project, persons mt adjustment time: the time for contractors to adjust management team, months mt turnover rate: the turnover rate of management team per month, persons per month mt wage: the average wage of management team, $ per person per hour net exp gain: experiences which are gained per month, experiences per month new memb exp gain: experiences which are gained from employing new project team members, experiences per month normal accident frequency: the historical or referential accident frequency of similar projects, events per person per month normal breakdown fraction: the historical or referential fraction of equipment breakdown of similar projects, per month normal equip prodty: the historical or referential equipment productivity of similar projects, tasks per unit per month normal exp: benchmark amount of experience for finding effect of cumulative experience on performance factors, experiences normal expectancy: the normal average time of equipment in operation, months normal invested equip fraction: the historical or referential fraction of invest equipment units, dimensionless normal labor prodty: the historical or referential labor productivity of similar projects, tasks per person per month normal major equip mtn unit cost: the normal maintenance costs per major equipment unit per month, $ per unit per month normal major equip operate unit cost: the normal operation costs per major equipment unit per month, $ per unit per month normal mgt fraction: the normal proportion of management team and total workforce, dimensionless normal mt turnover fraction: the normal turnover fraction of management team, per month normal overhead fraction: the normal fraction of overhead costs, dimensionless normal progress rate: the historical or referential progress rate of similar projects, tasks per month normal rework: the historical or referential rework of similar projects, dimensionless 151 normal sub equip: the historical or referential supportive equipment units of similar projects units normal sup equip mtn unit cost: the normal maintenance costs per supportive equipment unit per month, $ per unit per month normal sup equip operate unit cost: the normal operation costs per supportive equipment unit per month, $ per unit per month normal sw turnover fraction: the normal turnover fraction of skilled workers, per month normal sw/uw fraction: the historical or referential proportion of skilled and unskilled workers in similar projects, dimensionless normal uw turnover fraction: the normal turnover fraction of unskilled workers, per month normal waste fraction: the normal fraction of material wastes and material usage, dimensionless normal wokmonth: the reference work month length, hours per month onsite training rate: the number of unskilled workers is trained per month, persons per month operation cost: the costs for operating equipment and plant per month, $ per month order rate: the rate at which materials are ordered, units per month overhead fraction: the proportion of overhead costs and project costs, dimensionless overtime: the total number of hours that project team members have to work overtime per month, person*hours per month overtime cost: the labor costs for overtime, $ per month overtime index: the ratio which indicates the degree of overtime in order to measure workers’ fatigue, dimensionless overtime premium: a multiplier to labor costs and a ratio of overtime wages and straight time wages, dimensionless productive material cost: material costs for productive material only, $ per month productive material rate: the rate at which materials are used for productive works, units per month progress rate: the number of tasks completed per month and calculated by the minimum of labor progress rate and equipment progress rate, tasks per month Project cost to date: the actual cost of work performed (ACWP), $ Project deadline: the project duration specified in a contract and can be adjusted due to change orders and approval by owners, months project estimated cost: the forecasted project cost based upon actual costs, $ qual gap effect on mt: a nonlinear relationship which indicates the effect of quality gap on management team adjustments, dimensionless qual gap effect on sw/uw: a nonlinear relationship which indicates the effect of quality gap on skilled/unskilled workers adjustments, dimensionless quality gap: the difference between the project quality goal and current known quality, dimensionless Quality goal: the fraction of tasks without defects which is the project objective, dimensionless 152 quality goal adjust time: the time for contractors to adjust quality goal in response the quality gap, months quality of practice: the relative performance of the work without error, as influenced by project conditions such as experience, fatigue and supervision, dimensionless real equip prodty: equipment productivity not counting flawed tasks, tasks per unit per month real labor prodty: labor productivity not counting flawed tasks, tasks per unit per month repair time: the average time for mechanic to repair major equipment and plant, months report labor prodty time: the time for management team to record and prepare labor productivity reports, months Reported equip prodty: the equipment productivity that is reported in interval by project team, tasks per unit per month Reported labor prodty: the labor productivity that is reported in interval by project team, tasks per unit per month reported material time: the time for management team to record and prepare material usage reports, months reported material use rate: the rate at which materials are used onsite, units per month resource leveling: a nonlinear relationship which levels both manpower and major equipment input, dimensionless return fraction: the proportion of unaccepted materials which are returned to suppliers, dimensionless return rate: the rate at which unaccepted materials are returned to suppliers, units per month rework discovery rate: the rate at which materials are inspected by quality assurance, tasks per month rework material cost: the costs of materials which are used for rework, $ per month rework material rate: the rate at which materials are used for rework, units per month SAVEPER: the frequency with which output is stored, default in Vensim, month schedule pressure: the ratio of the scheduled completion date estimated by contractors and the project deadline specified by owners, dimensionless scheduled completion date: the duration required to complete a project and estimated and updated by contractors, months scope change rate: the rate at which project scope is averagely changed, tasks per month Skilled workers: the number of skilled workers who are employed to perform project, persons skills effect on accident: a nonlinear relationship which indicates the effect of skills on accident frequency, dimensionless skills effect on labor prodty: a nonlinear relationship which indicates the effect of skills on labor productivity, dimensionless skills effect on rework: a nonlinear relationship which indicates the effect of skills on rework, dimensionless skills effect on waste: a nonlinear relationship which indicates the effect of skills on material wastes, dimensionless skills fraction: the proportion of skilled workers and all workers, dimensionless 153 sp effect on accident: a nonlinear relationship which indicates the effect of schedule pressure on accident frequency, dimensionless sp effect on equip prodty: a nonlinear relationship which indicates the effect of schedule pressure on equipment productivity, dimensionless sp effect on labor prodty: a nonlinear relationship which indicates the effect of schedule pressure on labor productivity, dimensionless sp effect on rework: a nonlinear relationship which indicates the effect of schedule pressure on rework, dimensionless sp effect on waste: a nonlinear relationship which indicates the effect of schedule pressure on material wastes, dimensionless sp effect on workmonth: a nonlinear relationship which indicates the effect of schedule pressure on work-month, dimensionless stock coverage time: the time to reserve materials on storage onsite, months stock effect on equip sought: a nonlinear relationship which indicates the effect of material availability on seeking equipment, dimensionless stock effect on wf sought: a nonlinear relationship which indicates the effect of material availability on seeking manpower, dimensionless stock goal: the reserved material units which are the objective of contractors, units stock goal difference: the variance between stock goal and materials in storage, units straight time: hours worked within the limit of 208 per month per person, persons*hour per month straight time cost: the cost incuured due to non overtime work, $ per month sup equip adjustment time: the time for contractors to adjust supportive equipment, months sup equip de unit: the depreciation cost of a supportive equipment unit per month, $ per month per unit sup equip effect on labor progress: a nonlinear relationship which indicates the effect of supportive equipment on labor progress, dimensionless sup equip sought: the number of supportive equipment which is sought for a project, units supervision effect on accident: a nonlinear relationship which indicates the effect of supervision on accident frequency, dimensionless supervision effect on prodty: a nonlinear relationship which indicates the effect of supervision on labor and equipment productivity, dimensionless supervision effect on rework: a nonlinear relationship which indicates the effect of supervision on rework, dimensionless supervision effect on waste: a nonlinear relationship which indicates the effect of supervision on material wastes, dimensionless supervision index: the degree of supervision on construction site, dimensionless Supportive equipment: the supportive equipment units that are operating onsite, units sw adjustment time: the time for contractors to adjust the number of skilled workers, month sw turnover rate: the turnover rate of skilled workers, persons per month sw wage: the average wage per hours of skilled workers, $ per person per hour 154 sw/uw fraction: the proportion of skilled workers and all workers decided by contractors, dimensionless time estimated required: the time by which contractors estimated until project completion, months time remain effect on invest equip: a nonlinear relationship which indicates the effect of time remaining on equipment investment, dimensionless time remaining: the time remains base upon the project deadline and current date, months TIME STEP: the time step for the simulation, default in Vensim, month time to discover defects: the duration between the tasks performed and inspections of these tasks by quality assurance, months training fraction: the proportion of unskilled workers who are trained onsite, dimensionless Undiscovered rework: the flawed works which are not discovered yet, tasks Unskilled workers: the number of unskilled workers who are employed for a project, persons uw adjustment time: the time for contractors to adjust the number of unskilled workers, month uw tunover rate: the turnover rate of unskilled workers, persons per month uw wage: the average wage per hours of unskilled workers, $ per person per hour waste material cost: the costs of materials which are wasted, $ per month waste material: material units which are wasted, units per month WF sought: the number of workforce who are sought to fulfill the project progress, persons Work accomplished: the sum of tasks performed including tasks performed that are not taken over yet, tasks Work remaining: tasks workers sought: the number of workers who are sought to fulfill the project progress, persons workforce: the total of project team members on construction site, persons workmonth: the average number of hours worked in each month by each project member onsite, hours per month workmonth avg time: the time over which the average work-month is computed This variable is used to find the degree of workers’ fatigue, months workmonth effect on mtn: a nonlinear relationship which indicates the effect of workmonth on the costs of equipment maintenance, dimensionless 155 ... performance, client satisfaction, functionality, contractor satisfaction and project manager/team satisfaction 2.4 Applications of System Dynamics in Management 2.4.1 The Roles of System Dynamics. .. of system and policy variables Aggregating patterns and defining system boundary Recognition of a fabric of past trends for system variables 12 Recognition of a fabric of past trends for system. .. that system dynamics must be a promising approach in construction project management System dynamics has been realized as a proven approach to project management and hence construction project management