Comprehensive maintainability scoring system (COMASS) for commercial buidings in tropical climate of singapore 1

Research objectives was set as 3 deliverables: 1 Defect Library DL to improve the knowledge on building defects; 2 Maintainability Handbook to benchmark design-construction-maintenance p

COMPREHENSIVE MAINTAINABILITY SCORING SYSTEM (COMASS) FOR COMMERCIAL BUILDINGS IN

TROPICAL CLIMATE OF SINGAPORE

SUTAPA DAS

NATIONAL UNIVERSITY OF SINGAPORE

2008

COMPREHENSIVE MAINTAINABILITY SCORING SYSTEM (COMASS) FOR COMMERCIAL BUILDINGS IN

TROPICAL CLIMATE OF SINGAPORE

SUTAPA DAS

(B.Arch (Hons.), JU; M.Tech, IIT Madras)

A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

DEPARTMENT OF BUILDING NATIONAL UNIVERSITY OF SINGAPORE

2008

First of all I would like to specially mention about my supervisor and mentor Prof Michael

Yit Lin Chew; my thesis committee members Dr Wong Nyuk Hien and Dr Evelyne Teo

Without them nothing was possible Dr Poh Kim Leng from Dept of Systems & Industrial

Engineering provided an extraordinary guidance in a critical part of this research

I am deeply indebted to the following treasured personalities for their help in one way or other:

● Ms Nayanthara De Silva (University of Moratowa)

● Dr Kang Kok Hin (Institute of Facilities Management)

● Other professors and staffs of Dept of Building, National University of Singapore

● Industry experts from several prestigious facility management organizations

● My students: Adeline, Fong Yee, Hoe Kiat, Nur Hafizah, Tsz Shan and Wen Tirng

● My colleagues: Benson, Bin, Jovan, Shams, Swei Mei and many others

I pay my gratitude to my family members - my husband, mom and mom-in-law for providing uncompromising moral strength to sail through all ups and downs The last but not the least mention is my late father – whom I could not even bid a farewell He wanted me to fulfil my academic responsibility and silently left his blessings

SUMMARY

Growing complexity of building systems and higher user requirements have prioritized maintainability over maintenance especially for commercial building sector in order to attract and retain clients A thorough literature review indicated that unlike sustainability, there is no comprehensive maintainability scoring system (COMASS) to predict maintainability potential

of buildings In spite of good design-construction-maintenance guidelines, recurrent defects keep buildings under constant maintenance, putting users’ health and safety at stake apart from affecting economy and system performance This paradox has been attributed to dearth of: (1) knowledge database of defects; (2) system selection framework and (3) communication

Proposed COMASS addresses this knowledge gap It is a decision-enhancement tool aimed for part or whole of a new or existing building for selecting the best strategy to ‘design out’ defects Research objectives was set as 3 deliverables: (1) Defect Library (DL) to improve the knowledge on building defects; (2) Maintainability Handbook to benchmark design-construction-maintenance practices along with maintainability score (MS); and (3) integration

of building elements and life cycle phases into COMASS

Commercial buildings of Singapore for its key elements under central facility management were studied Qualitative FMECA (Failure Mode Effects and Criticality Analysis) was selected for defect grading Building was divided into nine major subsystems grouped into two main systems: (1) civil-architectural or C&A (basement, facade, wet-area and roof) and (2) mechanical-electrical or M&E (sanitary-plumbing, HVAC, elevator, electrical and fire-protection) From 14 detailed case studies and interview with 34 facility managers (FM), 319 defects pertaining to 62 major components of these subsystems were identified Their causes were analyzed in terms of (1) design/ specification; (2) construction/ installation; (3) maintenance; and (4) external factors About 45.5% defects were found critical based on their frequency and severity (impacts on economy, system performance and health-safety-comfort)

Maintainability guidelines comprised of 731 defect-mitigating checklist factors was developed from literature and DL They were grouped into life-cycle phases and further subgrouped under components of subsystem Factors’ relative weights (RW) are their ability

to mitigate both critical and non-critical defects Weighted sum of the MS of each factor indicates MS for individual sub-system, where a higher score means higher maintainability

For integration of subsystems into COMASS w.r.t both objective and subjective parameters, AHP (analytic hierarchy process) using interview and questionnaire was critically selected Eleven consistent results were used to determine 12 sets of RWs for 9 subsystems for various location-height combinations Seamless matching of objective result with experts’ subjective opinion proved the integration process logical and comprehensive Predictive accuracy of COMASS was found satisfactory through operational validity and sensitivity test via Monte Carlo simulation A prototype multi-tenant office tower at CBD was modelled

COMASS is the first attempt in building maintainability for holistic integration of phases of building lifecycles and components From existing defects, COMASS evaluated the entire decision making process of building life cycle and reflected back the same on performance Hence COMASS was able to bridge the knowledge gap between theoretical guidelines and their real life implication This research further highlighted that performance, not cost was the main governing factor in facility management The standard of performance based on both objective and subjective parameters imposes different emphasis of different building components This decision–enhancement tool empowered with a user friendly, performance based online version (www.hpbc.bdg.nus.edu.sg) aspires to improve the quality of building industry significantly The generic method is applicable to other building types and climates Further refinement with real-life testing, consideration of chain effect of defects to the fullest extent and time-dependent decision making were identified as the scope of future research

Keywords: AHP, Benchmarking, Defects, FMECA, Maintainability, Scoring system

TABLE OF CONTENTS

Acknowledgements ……… i

Summary ……… ii

Table of Contents ……… iv

List of Tables ……… ix

List of Figures ……… xiv

List of Acronyms ……… xvii

CHAPTER 1 INTRODUCTION ……… 1

1.1 Background ……… 1

1.1.1 The concept of maintainability and maintenance ……… 1

1.12 Significance of maintainability ……… 2

1.1.3 Research problem – A paradoxical situation in Singapore………… 2

1.1.4 Rationale of the study ……… 4

1.1.4.1 Dearth of knowledge database of defect ……… 4

1.1.4.2 Dearth of system selection framework ……… 5

1.1.4.3 Lack of communication ……… 6

1.2 Research guideline ……… 6

1.2.1 Knowledge gap ……….… 7

1.2.2 Aim and Objectives ……… 7

1.2.3 Hypothesis ……… 7

1.2.4 Scope of Research ……… 7

1.2.5 Knowledge Contribution ……… 9

1.2.6 Practical Implication ……… 9

1.3 Definition of terms ……… 10

1.4 Organisation of the thesis ……… 10

1.5 Summary ……… 12

CHAPTER 2 LITERATURE REVIEW ……… 13

2.1 Introduction ……… 13

2.2 Building components in terms of maintainability ……… 14

2.3 Building maintenance ……… 16

2.3.1 Objectives of maintenance ……… 16

2.3.2 Decision support frameworks in maintenance ……… …… 17

2.4 Maintainability ……… 21

2.4.1 Objectives of maintainability ……… 21

2.4.2 Maintainability in building research ……… 21

2.5 Maintainability tools in system engineering ……… 23

2.5.1 Fault Tree Analysis (FTA) ……… 23

2.5.2 Fishbone Diagram ……… … 24

2.5.3 Failure Mode Effect and Criticality Analysis (FMECA) ………… 24

2.5.4 FMECA in building sector ……… 27

2.6 Existing building grading systems ……… 28

2.6.1 Classification of grading system ……… 28

2.6.1.1 First generation: pass-fail ……… 30

2.6.1.2 Second generation: simple additive ……… 30

2.6.1.3 Third generation: weighed additive ……… 30

2.6.1.3 Others ……… 32

2.7 Principles for weighing and aggregation of multiple parameters ……… 34

2.7.1 Equal weight ……… 35

2.7.2 Weights based on statistical models ……… 35

2.7.3 Weights based on opinions: MCDA methods ……… 36

2.7.4 Comparisons of the methods ……… 39

2.8 Knowledge gap ……… 40

2.9 Summary ……… 41

CHAPTER 3 RESEARCH METHODOLOGY ……… 42

3.1 Introduction ……… 42

3.1.1 Brief overview of research methodology ……… 42

3.2 Phase 1: Conception ……… 42

3.3 Phase 2: Individual maintainability scoring ……… 44

3.3.1 Selection of defect grading strategy ……… 44

3.3.2 Development of criticality parameters ……… 45

3.3.3 Selection of respondent and sampling frame ……… 46

3.3.4 Site Investigation ……… 47

3.3.5 Questionnaire design and pilot survey ……… 48

3.3.6 Main survey ……… 49

3.3.7 Proposed Defect Library (cause and criticality analysis) ………… 50

3.3.8 Maintainability Handbook and subsystem grading ……… 51

3.4 Phase 3: Integration of building subsystems into COMASS ……… 52

3.4.1 Selection of AHP as suitable technique for integration ……… 53

3.4.2 Construction of hierarchy ……… 55

3.4.2.1 Goal ……… 55

3.4.2.2 Criteria ……… 56

3.4.2.3 Sub-criteria under location ……… 56

3.4.2.4 Sub-criteria under height ……… 57

3.4.2.5 Mutual exclusiveness of sub-criteria ……… 57

3.4.2.6 Alternatives ……… 57

3.4.3 Development of questionnaire ……… 58

3.4.4 Selection of respondents and sample size ……… 60

3.4.5 Data collection – survey & interview ……… 60

3.4.6 Data analysis and global weight (GW) calculation ……… 61

3.4.6.1 Inconsistency ratio ……… 61

3.4.6.2 Aggregation of results ……… 62

3.4.6.3 Derivation of global weights from local weights ……… 62

3.4.7 Development of COMASS ……… 63

3.5 Phase 4: Conclusion ……… 64

3.5.1 Checking the predictive accuracy ……… 64

3.5.1.1 Validation ……… 64

3.5.1.2 Sensitivity analysis ……… 66

3.5.1.3 The proposed testing method for COMASS ……… 66

3.5.2 Practical application ……… 67

3.5.3 Conclusion and recommendation ……… 67

3.6 Summary ……… 67

CHAPTER 4 DEFECT ANALYSIS ……… 68

4.1 Introduction ……… 68

4.2 General findings of questionnaire survey ……… 68

4.2.1 Demographic information ……… 68

4.2.2 Significance of grading criteria and building subsystems ………… 70

4.2.3 Format of defect reporting ……… 70

4.3 Defects in basement ……… 71

4.3.1 Criticality analysis of defects in basement ……… 74

4.4 Defects in facade ……… 75

4.4.1 Criticality analysis of defects in facade ……… 83

4.5 Defects in wet area ……… 85

4.5.1 Criticality analysis of wet area defects ……… 89

4.6 Defects in roof ……… 89

4.6.1 Criticality analysis of defects in roof ……… 94

4.7 Defects in sanitary-plumbing system ……… 95

4.7.1 Criticality analysis of defects in sanitary-plumbing system ……… 101

4.8 Defects in HVAC system ……… 102

4.8.1 Criticality analysis of defects in HVAC system ……… 107

4.9 Defects in elevators (or lifts) ……… 108

4.9.1 Criticality analysis of defects in elevators ……… 114

4.10 Defects in electrical system ……… 116

4.10.1 Criticality analysis of defects in electrical system ……… 122

4.11 Defects in fire protection system ……… 123

4.11.1 Criticality analysis of defects in fire protection system ……… 128

4.12 Comparison of causes and criticality of building subsystems ……… 129

4.13 Summary ……… 131

CHAPTER 5 MAINTAINABILITY SCORING FOR BLDG SUBSYSTEMS 132 5.1 Introduction ……… 132

5.2 General format of maintainability scoring ……… 132

5.2.1 Mathematical principle ……… 132

5.2.2 Maintainability Handbook ……… 133

5.3 Maintainability scoring for basement ……… … 133

5.4 Maintainability scoring for facade ……… 135

5.5 Maintainability scoring for wet area ……… 137

5.6 Maintainability scoring for roof ……… 139

5.7 Maintainability scoring for sanitary-plumbing system ……… 141

5.8 Maintainability scoring for HVAC system.……… 144

5.9 Maintainability scoring for elevators ……… 146

5.10 Maintainability scoring for electrical system ……… 149

5.11 Maintainability scoring for fire protection system ……… 152

5.12 Overview of scoring of all subsystems ……… 154

5.13 Summary ……… 154

CHAPTER 6 COMPREHENSIVE MAINTAINABILITY SCORING SYSTEM 155 6.1 Introduction ……… 155

6.2 Data analysis ……… 155

6.2.1 Data processing in ExpertChoice (EC 11.5) ……… 155

6.2.2 Dealing with inconsistency ……… 157

6.2.3 Selection of threshold limit of IR and the best dataset ……… 158

6.2.3.1 Preliminary test result ……… …… 159

6.2.3.2 Statistical test result ……… 159

6.2.3.3 Rank reversal ……… 160

6.2.3.4 Selection between Dataset 1 and 4 ……… 160

6.2.4 Derivation of GW from LW ……… 161

6.3 Results and discussion ……… 163

6.3.1 Influence of criteria: location and height ……… 163

6.3.2 Influence of sub-criteria: location ……… 163

6.3.3 Influence of sub-criteria: height ……… 165

6.3.4 Relative importance of C&A and M&E systems……… 166

6.3.4.1 Influence of location on C&A and M&E systems……… 166

6.3.4.2 Influence of height on C&A and M&E systems ……… 167

6.3.5 Relative importance of all nine subsystems ……… 168

6.3.5.1 Rank 1: HVAC system ……… 170

6.3.5.2 Rank 2: Elevator system ……… 170

6.3.5.3 Rank 3: Facade ……… 171

6.4 Application of GW in COMASS ……… 171

6.4.1 Example of a calculation in COMASS ……… 171

6.5 Summary ……… 172

CHAPTER 7 TESTING AND APPLICATION ……… 173

7.1 Introduction ……… 173

7.2 Operational validity ……… 173

7.2.1 Details and specification of the prototype building ……… 173

7.2.2 Scoring for basement ……… 174

7.2.3 Scoring for facade ……… 176

7.2.4 Scoring for wet area ……… 178

7.2.5 Scoring for roof ……… 180

7.2.6 Scoring for sanitary-plumbing system ……… 182

7.2.7 Scoring for HVAC system ……… 185

7.2.8 Scoring for elevators ……… 187

7.2.9 Scoring for electrical system ……… 189

7.2.10 Scoring for fire protection system ……… 192

7.2.11 Scoring for entire building ……… 195

7.3 Sensitivity analysis via Monte Carlo simulation ……… 196

7.4 Web based application of COMASS ……… 197

7.4.1 Defect Library ……… 197

7.4.2 Maintainability Scoring System ……… 198

7.5 Summary ……… 200

CHAPTER 8 CONCLUSIONS ……… 201

8.1 Introduction ……… 201

8.2 Research summary showing achievement of research goal……… 201

8.3 Key findings ……… 203

8.4 Knowledge contribution ……… 205

8.5 Industry contribution ……… 207

8.6 Limitation of the study ……… 208

8.7 Scope for future research ……… 208

8.8 Concluding remarks ……… 209

BIBLIOGRAPHY ……… 210

APPENDIXES ……… 240

Appendix A Survey questionnaires ……… 240

Appendix B Results of defect rating survey ……… 251

Appendix C1 Maintainability guidelines for basement ……… 275

Appendix C2 Maintainability guidelines for facade ……… 288

Appendix C3 Maintainability guidelines for wet area ……… 307

Appendix C4 Maintainability guidelines for roof ……… 319

Appendix C5 Maintainability guidelines for sanitary-plumbing system ………… 331

Appendix C6 Maintainability guidelines for HVAC system ……… 347

Appendix C7 Maintainability guidelines for elevators ……… 358

Appendix C8 Maintainability guidelines for electrical system ……… 371

Appendix C9 Maintainability guidelines for fire-protection system ……… 390

Appendix D AHP survey results ……… 404

Appendix E Results of sensitivity test by Monte Carlo simulation ……… 410

LIST OF PUBLICATIONS ……… 414

LIST OF TABLES

2.1 Difference between C&A and M&E systems ……… 14

2.2 Class or rank for rating failure mode ……… 26

2.3 Summary of major grading systems ……… 29

2.4 Setting weights for criteria of GBTool) ……… 32

2.5 Random Consistency Index ……… ……… 38

2.6 Comparison of major MCDA methods ……… 39

2.7 Summary of findings from literature review ……… 40

3.1 Rating class of building defects ……… 46

3.2 Various location options used in AHP model ……… 56

3.3 The 9-point pair-wise comparison scale (Saaty, 1996) ……… 59

3.4 Structure of AHP questionnaire ……… 59

4.1 Details of case study buildings ……… 69

4.2 Significance of grading criteria and building subsystems ……… 70

4.3 Common defects in basement and their causes ……… 73

4.4 Criticality analysis defects in basement ……… 75

4.5 Common defects in facade and their causes ……… 78

4.6 Criticality analysis defects in facade ……… 84

4.7 Common defects in wet area and their causes ……… 85

4.8 Criticality analysis defects in wet area ……… 89

4.9 Common defects in flat roof and their causes ……… 91

4.10 Criticality analysis defects in roof ……… 95

4.11 Common defects in sanitary-plumbing system and their causes ……… 97

4.12 Criticality analysis defects in sanitary-plumbing system ……… 101

4.13 Common defects in HVAC system and their causes ……… 104

4.14 Criticality analysis defects in HVAC system ……… 108

4.15 Common defects in elevator and their causes ……… 110

4.16 Calculation of criticality index (Cr) of defects in elevator ……… 114

4.17 Common defects in electrical system and their causes ……… 118

4.18 Criticality analysis of defects in electrical system ……… 122

4.19 Common defects in fire protection system and their causes ……… 125

4.20 Criticality analysis defects in fire protection system ……… 128

4.21 Average % of defects for C&A and M&E systems ……… 131

5.1 Maintainability factors for basement and their RWs ……… 134

5.2 Maintainability factors for facade and their RWs ……… 136

5.3 Maintainability factors for wet area and their RWs ……… 138

5.4 Maintainability factors for roof and their RWs ……… 140

5.5 Maintainability factors for sanitary-plumbing system and their RWs ……… 142

5.6 Maintainability factors for HVAC system and their RWs ……… 144

5.7 Maintainability factors for elevator and their RWs ……… 147

5.8 Maintainability factors for electrical system and their RWs ……… 149

5.9 Maintainability factors for fire protection system and their RWs ………… 152

5.10 No of maintainability factors ……… 154

6.1 Six classifications of data set ……….……… 157

6.2 Illustrative example of IR chart ……… 158

6.3 Rank reversal with change in IR ……….……… 160

6.4 Renormalized LW of for all zone-height combinations ……… 161

6.5 Derivation of GW for location = residential zone and height = low ……… 162

6.6 GWs of building subsystems for all location-height combinations ………… 162

6.7 Ranking of nine subsystems for all locations and heights ……… 169

6.8 Application of GW in calculation of final score ……… 172

Table Description Page

7.1 Prototype scoring for basement ……….……… 174

7.2 Prototype scoring for facade ……….……….………… 177

7.3 Prototype scoring for wet area ……….……… 179

7.4 Prototype scoring for roof ……… 181

7.5 Prototype scoring for sanitary-plumbing system ……… 183

7.6 Prototype scoring for HVAC system ……….……… 185

7.7 Prototype scoring for elevators ……….……… 188

7.8 Prototype scoring for electrical system ……….……… 190

7.9 Prototype scoring for fire protection system ……….……….…… 193

7.10 Prototype scoring for entire building ……….……… 195

C.1.1 Grading for waterproofing system selection ……….……… 275

C.1.2 Grading for design of structural concrete ……….……… 276

C.1.3 Grading for design of tanked protection (Type A) system ……… 278

C.1.4 Grading for design of waterstops ……….……… 279

C.1.5 Grading for design of cavity ……… 280

C.1.6 Grading for design of drainage ……….……… 281

C.1.7 Grading for design of flooring ……….……… 282

C.1.8 Grading for selection of wall finishes ……….……… 282

C.1.9 Grading for consideration for ancillary facilities ……….……… 282

C.1.10 Grading for construction of structural concrete ……… 283

C.1.11 Grading for installation of water proofing membrane (Type A) ……… 284

C.1.12 Grading for installation of waterstops ……….……… 284

C.1.13 Grading for construction of cavity ……….……… 284

C.1.14 Grading for construction of flooring ……… 285

C.1.15 Grading for application of wall finishes ……… 286

C.1.16 Grading for maintenance ……… 287

C.1.17 Guideline for maintenance of internal and cavity drainage ……… 287

C.2.1 Grading for wall system selection ……… 288

C.2.2 Grading for weather resistance ……… 289

C.2.3 Grading for wall finishes selection ……… 290

C.2.4 Grading for wall joints ……… ……… 292

C.2.5 Design of expansion joint ……… 294

C.2.6 Grading for sealant detail ……… 294

C.2.7 Grading for accessibility design ……… 295

C.2.8 Grading for design of access system ……… 296

C.2.9 Grading for window design ……… 296

C.2.10 Grading for consideration for ancillary facilities ……… 299

C.2.11 Grading for construction of masonry ……… 299

C.2.12 Grading for erection of PC cladding ……… 300

C.2.13 Grading for erection of cladding ……… 302

C.2.14 Grading for application of sealant ……… 303

C.2.15 Grading for regular maintenance of facade ……… 304

C.2.16 Guidelines for maintenance of exposed brick wall ……… 304

C.2.17 Guidelines for maintenance of concrete and plastered wall ……… … 304

C.2.18 Guidelines for maintenance of painted wall: gloss/ semi-gloss enamels …… 305

C.2.19 Guidelines for maintenance of tiled wall ……… 305

C.2.20 Guidelines for maintenance of natural stone wall ……… 305

C.2.21 Guidelines for maintenance of glass (curtain wall & window) ……… 305

C.2.22 Guidelines for maintenance of metal cladded wall ……… 306

C.3.1 Grading for design of floor ……… 307

C.3.2 Grading for waterproofing selection ……… 308

C.3.3 Grading for detailing of waterproofing ……… 309

C.3.4 Grading for design of piping layout ……… 311

Table Description Page

C.3.5 Grading for design of fixture and fittings ……… 312

C.3.6 Grading for design of floor and wall tiles ……… 313

C.3.7 Grading for selection of paint ……… 314

C.3.8 Grading for design consideration of ancillary facilities ……… 315

C.3.9 Grading for construction of slope in floor ……… … 315

C.3.10 Grading for installation of waterproofing ……… … 315

C.3.11 Grading for installation of finishes (tiles) ……… 316

C.3.12 Grading for installation of fixture and fittings ……… 317

C.3.13 Grading for regular maintenance of wet area ……… 317

C.3.14 Guidelines for maintenance of wall and floor finishes ……… 318

C.3.15 Guidelines for maintenance of fixture and fittings ……… …… 318

C.4.1 Grading for selection of roofing systems ……… 319

C.4.2 Grading for design of concrete deck ……… 320

C.4.3 Grading for selection of waterproofing membrane ……… …… 321

C.4.4 Grading for detailing of waterproofing membrane ……… …… 322

C.4.5 Grading for design of insulation ……… 323

C.4.6 Grading for sealant detail ……… 324

C.4.7 Grading for design of drainage ……… 324

C.4.8 Grading for design of drainage outlets and RWDP ……… …… 325

C.4.9 Grading for design consideration of ancillary facilities ……… 326

C.4.10 Grading for construction of deck ……… 326

C.4.11 Grading for installation of waterproofing ……… 327

C.4.12 Grading for laying the thermal insulation & protective surface ……… 328

C.4.13 Grading for installation of drainage system ……… 329

C.4.14 Grading for maintenance ……… 329

C.4.15 Guideline for maintenance of roof ……… 330

C.5.1 Grading for water supply piping system ……… 331

C.5.2 Grading for hot water supply ……… 333

C.5.3 Grading for design of storage tank ……… 335

C.5.4 Grading for design of general and sewage pumps ……… 336

C.5.5 Grading for design of sanitary appliances ……… 336

C.5.6 Grading for design of sanitary piping ……… ……… 337

C.5.7 Grading for design of sewage ejector & solid diverter tank ……… 339

C.5.8 Grading for design of sewer drains ……… 339

C.5.9 Grading for installation of water supply piping ……… ……… 341

C.5.10 Grading for construction of water storage ……… 341

C.5.11 Grading for installation of pumps ……… …… 342

C.5.12 Grading for installation of sanitary appliances ……… … 342

C.5.13 Grading for installation of sanitary piping ……… 343

C.5.14 Grading for installation of sewage ejector & solid diverter tank ……… 343

C.5.15 Grading for installation of sanitary piping ……… 343

C.5.16 Grading for maintenance of sanitary-plumbing system ……… 344

C.5.17 Guidelines for maintenance of sanitary-plumbing system ……… 344

C.6.1 Grading for design of AHU and FCU ……… ……… 347

C.6.2 Grading for design of FCU ……… ……… …… 349

C.6.3 Grading for design of chiller ……… ……… 350

C.6.4 Grading for design of cooling tower ……… 351

C.6.5 Grading for design of air distribution system ……… 352

C.6.6 Grading for installation of HVAC system components ……… 354

C.6.7 Grading for maintenance ……… 355

C.6.8 Guidelines for maintenance of AHU & FCU ……… 355

C.6.9 Guidelines for maintenance of chiller plant ……… 356

C.6.10 Guidelines for maintenance of cooling tower ……… 356

Table Description Page

C.6.11 Grading for maintenance of air distribution system ……… 356

C.7.1 Grading for planning of elevator ……… 358

C.7.2 Grading for design of machine room ……… 359

C.7.3 Grading for general design considerations for machines ……… 359

C.7.4 Grading for design of roping system ……… ……… 360

C.7.5 Grading for design of hoistway and its components ……… …… 362

C.7.6 Grading for design of elevator car or cab ……… 363

C.7.7 Grading for design of landing ……… 364

C.7.8 Grading for design of car door and lobby door ……… 364

C.7.9 Grading for design of lift pit ……… 364

C.7.10 Grading for consideration for ancillary facilities ……… 365

C.7.11 Grading for construction of structural elements ……… 365

C.7.12 Grading for installation of equipment ……… ……… 366

C.7.13 Grading for lubrication ……… 367

C.7.14 Grading for maintenance ……… 367

C.7.15 Guideline for maintenance of machine room and its equipment ……… 368

C.7.16 Guideline for maintenance of elevator car ……… 369

C.7.17 Guideline for maintenance of hoistway, landing and pit ……… 370

C.7.18 Guideline for maintenance of lobby and car door ……… ……… 370

C.8.1 Grading for design of system in general ……… 371

C.8.2 Grading for design of transformer ……… 372

C.8.3 Grading for design of cable conductor ……… 373

C.8.4 Grading for design of cable layout ……… 374

C.8.5 Grading for design of busway ……… 375

C.8.6 Grading for design of connectors ……… 376

C.8.7 Grading for design of distribution equipment ……… 376

C.8.8 Grading for design of protection device ……… ……… 378

C.8.9 Grading for design of lighting system ……… 379

C.8.10 Grading for design of standby and emergency power supply ……… 380

C.8.11 Grading for design of grounding system……… 381

C.8.12 Grading for design of LPS ……… 382

C.8.13 Grading for design consideration of ancillary facilities ……… 382

C.8.14 Grading for installation of transformer ……… ……… 382

C.8.15 Grading for installation of wiring system ……… 383

C.8.16 Grading for installation of distribution and protective device……… …… 384

C.8.17 Grading for installation of lighting ……… ……… 384

C.8.18 Grading for installation of emergency / standby power supply ……… 384

C.8.19 Grading for installation of grounding and LPS ……… …… 385

C.8.20 Grading for maintenance ……… 386

C.8.21 Guideline for maintenance of wiring system ……… …… 387

C.8.22 Guideline for maintenance of distribution equipment ……… … 387

C.8.23 Guideline for maintenance of control & protective device ……… 388

C.8.24 Guideline for maintenance of lighting ……… 388

C.8.25 Guideline for maintenance of emergency / standby power supply ………… 388

C.8.26 Guideline for maintenance of grounding system & LPS ……… 389

C.9.1 Grading for detector selection ……… ……… 390

C.9.2 Grading for design of alarm system ……… 391

C.9.3 Grading for design of fire hydrant and accessories ……… 392

C.9.4 Grading for design of fire hose ……… ……… 392

C.9.5 Grading for design of sprinkler system ……… 393

C.9.6 Grading for selection of portable fire extinguisher ……… 394

C.9.7 Grading for design of fire door ……… 394

C.9.8 Grading for design of services for fire escape ……… 395

Table Description Page

C.9.9 Grading for installation of detector and alarm ……… 396

C.9.10 Grading for installation of fire hydrant and hose ……… 397

C.9.11 Grading for installation of sprinkler system ……… 397

C.9.12 Grading for installation of portable extinguisher ……… 398

C.9.13 Grading for installation of fire door ……… 398

C.9.14 Grading for maintenance ……… ……… 399

C.9.15 Guideline for maintenance of detector and alarm ……… ……… 399

C.9.16 Guideline for maintenance of fire hydrant and hose ……… ……… 400

C.9.17 Guideline for maintenance of sprinkler system ……… 400

C.9.18 Guideline for maintenance of portable fire extinguishers ……… 402

C.9.19 Guideline for maintenance of fire door ……… 402

C.9.20 Guideline for maintenance of services for safe escape ……… 403

LIST OF FIGURES

2.1 Elements of a building……… 15

2.2 ANN model for risk analysis of facade……… 23

2.3 Example of a sample Fault Tree Analysis……… 24

2.4 Example of a sample Fishbone Diagram……… 24

2.5 Typical example of FMECA hierarchy……… 25

2.6 Basic steps of FMECA……… 25

2.7 Criticality grid……… 26

2.8 Basic Structure of CASBEE……… 33

2.9 Graphical computation of BEE……… 34

2.10 A typical AHP hierarchy……… 38

3.1 Flowchart of research methodology ……… 43

3.2 ‘Visual cookies’ used to highlight building subsystems ……… 49

3.3 The hierarchy model for building maintainability ……… 55

3.4 Building height vs complexity of building systems ……… 58

3.5 Graphical symbols to denote various locations and height of the building … 59 4.1 Demography of the respondents ……… 69

4.2 Common defects in basement ……… 72

4.3 Common defects in facade ……… 76

4.4 Common defects in wet area ……… 88

4.5 Common defects in flat roof ……… 90

4.6 Common defects in sanitary-plumbing system ……… 96

4.7 Common defects in HVAC system ……… 103

4.8 Common defects in elevator ……… 109

4.9 Relationship of accidents of increasing severity of consequences ………… 116

4.10 Common defects in electrical system ……… 117

4.11 Common defects in fire protection system ……… 124

4.12 Comparison of defect causes and criticality of nine subsystems ……… 130

5.1 Schematic diagram of electrical system of commercial building ………… 149

6.1 Demography of the respondents ……… 155

6.2 Data procession in ExpertChoice (EC) ……….……… 156

6.3 Comparison of years of experience and consistency of results ……… 158

6.4 GW for nine –subsystems ……….……….……… 159

6.5 Variation of GWs with location, keeping the height constant ……… 164

6.6 Variation of GWs with height, keeping the Location constant ……… 164

6.7 RWs of various (a) locations and (b) heights ……….……… 165

6.8 RWs of C&A and M&E systems for various locations and heights ……… 166

6.9 RW of C&A and M&E systems with variance in (a) location and (b) height 167 6.10 Relative weights of C&A systems for various locations and heights ……… 168

6.11 Relative weights of M&E systems for various locations and heights ……… 168

7.1 Variance of MS and RW for subsystems ……….……… 196

7.3 Interface of ‘Maintainability of Buildings’ website ……… 198

7.4 Three level hierarchy of Defect Library interface ……… 198

7.5 Compilation of defects, photos and analysis of causes ……… 198

7.6 Interface of maintainability scoring system ……….……… 199

C.1.1 Various types of waterproofing systems……… 275

C.1.2 Penetration thru’ water/ vapour proofing membrane……… 279

C.1.3 Various types of water stops……… 279

C.1.4 Details of surface water drainage……… 281

C.1.5 Various pointing (L to R): flashed struck, keyed & recessed……… 285

C.2.1 Various types of wall system ……….……… 289

Fig Description Page

C.2.2 Drainage detail in curtain wall and cladding ……….……… 290

C.2.3 Various types of wall joint ……….……… 291

C.2.4 Various options of joint exposure ……….……… 292

C.2.5 Drainage detail in curtain wall ……….……… 293

C.2.6 Expansion joint details ……….……….……… 294

C.2.7 Sealant joint details ……….……….……… 294

C.2.8 Various window details ……….……….……… 298

C.2.9 Accessibility parameters of a window ……….……… 299

C.2.10 Various pointing (L to R): flashed struck, keyed & recessed……… 300

C.2.11 Sealant application: scraping, masking tape removal, tooling ……… 303

C.3.1 Zoning by using kerb and level difference……… 307

C.3.2 Typical detail for drainage……… ……… 307

C.3.3 Typical details of waterproofing in wet area……… 310

C.3.4 Example of multiple fixture connected to a single trap……… 311

C.3.5 Water closet: floor mounted and wall hung……… ……… 312

C.3.6 Leakage at the junction of discharge & gully pipe……… 317

C.4.1 Various types of roofing system ……….……….…… 319

C.4.2 Typical Joint and penetration details for waterproofing ………….………… 322

C.4.3 Typical detail of vent in BUR ……….……….……… 323

C.4.4 Formation of staggered side laps ……….……….…… 328

C.5.1 Connection to the top of the hot water cylinder ……… 333

C.5.2 Details of water supply pipe design ……….……….… 334

C.5.3 Location of storage tank ……….……….……… 335

C.5.4 Air gap ………….……….……….………… 336

C.5.5 Various types of trap seal details ……….……….…… 337

C.5.6 Details of branch ventilation pipe and cross venting ………….……… 337

C.5.7 Various types of sanitary pipe work systems ……….……… 338

C.5.8 Components of a Sewage ejector in a diverter tank………….… ………… 339

C.5.9 Backdrop and tumbling bay in IC/ MH connection………….……… 340

C.5.10 Laying of sewers ……….……….……… 344

C.6.1 Various types of air filters ……….……….……… 349

C.6.2 Various types of compressors ……….……….……… 350

C.6.3 Adequate size of access opening ……….……….…… 352

C.6.4 Various types of diffusers ……….……….……… 353

C.6.5 Damper blade arrangement: opposed and direct ………….……… 353

C.6.6 Checking alignment with K-bar and V-belt tension ………….……… 356

C.7.1 Various types of sheave groove ……….……….……… 360

C.7.2 Balance mechanism for suspension rope ………….……… 361

C.7.3 Rope configuration: 6-strands and 8-strands ………….……….……… 361

C.7.4 Various types of rope lays ……….……….……… 361

C.7.5 Straightness of guiderail……….……….……… 362

C.7.6 Example of general purpose passenger lift – small and big ………….…… 364

C.8.1 Schematic diagram of electrical system of commercial building ………… 371

C.8.2 Details of a standard busway……….……….………… 373

C.8.3 Cable through wall and joist ……….……….………… 375

C.8.4 Main loadcentre & main panel with sub-panel ……….………… 378

C.8.5 Earth reisitivity measurement - Four probe method ……… 385

C.9.1 Details of fire hose reel and cabinet ……….……… 393

C.9.2 Details of a fire door ……….……….……… 395

LIST OF ACRONYMS

IEEE Institution of Electrical & Electronics Engineers

Acronym Full Name

MH Manhole

SMCNA Sheet Metal & Air Conditioning Contractors' National Association

Chapter 1 Introduction 1.1 Background

1.1.1 The concept of maintainability and maintenance

The maintainability of buildings is a key initiative of Construction 21 or C21 – the blue print for reforming Singapore’s construction industry in 21st century (CTC, 1999) Much earlier in

1901 the concept of maintainability came into existence through US Army Signal Corps’ contract for Wright brothers’ airplane that stated that ‘ should be simple to operate and maintain’ (Dept of Defence, 1976) and the first book on maintainability was published in

1960 titled Electronic Maintainability (Ed F.L Akenbrandt)

Maintainability is a design characteristics and maintenance is the result of design (Blanchard, Verma & Peterson, 1995) British Standards Institute (BSI) defines maintainability as ‘the ability of an item, under conditions of use, to be retained in or restored to a state in which it can perform its required functions, when maintenance is performed under stated conditions and using prescribed procedures and resources’ (BS 3811) While building maintenance is defined by Chartered Institute of Building or CIB (1990) as ‘work undertaken in order to keep, restore, or improve every part of the building, its services and surrounds, to currently accepted standards, and to sustain the utility and value of the building’ Hence it can be inferred that conceptually maintainability and maintenance are inversely related i.e a building with high maintainability requires lesser maintenance and vice versa

Historically, maintenance has been considered as a ‘necessary evil’ - an obligatory cost burden for projects (Moua & Russell, 2001) But over time, this negative perception has changed to the main support for the core income generation activities of an organization (Quah, 1998) Hence defining maintenance by life cycle cost (LCC) has been replaced by

today’s context of higher user expectation, the performance based concept introduced by CIB (1990) has received a better acceptance than the theory proposed by BSI 3811 Finch (1998) argued that the BS 3811 definition fails to ‘address the obsolescence gap developed from increased functional and technological demands If this issue is not continually addressed, ultimately it leads to the building’s untimely demise’

1.1.2 Significance of maintainability

The notion of maintainability has been manifesting during the past decade because building owners demand more durable buildings As buildings start to deteriorate from the moment they are completed and incur maintenance cost (Arditi, & Nawakorawit, 1999b), proper maintenance should be planned to control and defer this inevitable process of deterioration (Chew, Tan & Kang, 2004) However maintenance of modern buildings with growing complexity, higher proportion of more sophisticated systems and higher level of service requirement (Shohet & Perelstein, 2004) together have resulted in ever increasing maintenance cost to be fitted in decreasing maintenance budget As a response to this scenario, maintainability has been prioritized over maintenance ever than before (Bourke & Davies, 1997; Cane, Morrison & Ireland, 1998; Cash, 1997a, b; Horner, El-Haram & Munns, 1997; Shohet, Puterman, & Gilboa, 2002, Underwood & Alshawi, 1999; Van Winden & Dekker, 1998)

1.1.3 Research problem – A paradoxical situation in Singapore

Maintainability has even higher significance in Singapore due to its tropical climate and economic profile Building components need additional maintenance in tropics as alternate dry and wet seasons shorten lifespan of materials to a great extent (Chew, Tan & Soemara, 2004) But standard of maintenance or more precisely the standard of building performance can not be compromised in Singapore as the country survives as the business hub of South East Asia It needs to compete and outwit other centres of growth such as, Shanghai, Hong Kong or Kuala Lumpur A global standard of facility is must in order to attract and retain

global clients (Moore & Finch, 2004; Tay, 2006) Direct maintenance expenditure for office buildings in the Central Business District has tripled in just 10 years (BCA, 2000; CIDB, 1999) Hence the paramount importance of maintainability in Singapore context is palpable

This fact was given official recognition through the formation of C21 committee which established maintainability as one of the key strategic thrusts and proposed strongly the establishment of a maintainability assessment system to grade the performance of buildings as

a major step to upgrade the service level of Singapore construction industry (CTC, 1999) Apart from this, codes, standards and performance based initiatives customised for Singapore climate and construction industry have been planned profoundly During a short period of

1999 - 2005, total ten schemes have been implemented for benchmarking, grading, government incentive / penalty and recommendations for buildable design, improved workmanship and energy efficiency (Das, 2007) But the output is not as commendable as it was expected In a research project titled ‘Maintainability of Buildings in the Tropics’ by Building & Construction Authority (BCA) and National University of Singapore (NUS) in 2002-2004, condition survey of 450 buildings aged between 1-30 years and with height range

of 4–60 storeys was conducted It revealed that defects are prevalent in almost all major building elements - keeping them under constant maintenance Facade and wet area itself demonstrated 51 and 14 defects respectively (Chew, De Silva & Tan, 2004; Chew, 2005) A bigger surprise came through Chong & Low’s (2006) work They found more than 18,704 defects in 74 buildings 2 - 6 years old i.e in an average more than 250 defects per building that are almost new

This is an alarmingly high number especially in a country like Singapore where (1) user expectation and possible drawbacks are well defined; (2) building guidelines are advanced and (3) their implementation is strictly enforced by law (Donohoe, 1999) Hence it was apparent that there was a missing component causing an imbalance between the input and

output This is a paradoxical situation requiring urgently a probing investigation and thus led

to the following research questions:

1 What are the key factors that affect maintainability and how do they influence?

2 How to measure maintainability to select best building alternative?

1.1.4 Rationale of the study

While searching answers for the research questions, it was realized that a few major hurdles

to be overcome before reaching a conclusion These roadblocks as mentioned by previous researchers (Arditi, et al, 1999b; De Silva, Dulaimi, Ling, & Ofori, 2004; Korka, Oloufa & Thomas, 1997) are:

● Dearth of knowledge database of defect

● Dearth of system selection framework

● Lack of communication

1.1.4.1 Dearth of knowledge database of defect

Defects are responsible for poor maintainability which is a composite of many factors, namely, (1) systems and designs; (2) materials; (3) performance; (4) the risk of failures associated with systems and components (Chew & De Silva, 2004) These root causes can be further elaborated as design, detailing, material, construction quality, micro-environment, and maintenance practices (Gambardella & Moroni, 1990; Honstede, 1990; Olubodun, 1996) Design, construction and maintenance were accountable for 40%, 30% and rest 30% of building defects in Hong Kong (Lam, 2000) In Singapore this ratio was 84% (design 60% + material 24%), 33% and 4% as well as few defects with multiple causes (Chong & Low, 2006) Though maintenance is the longest phase of building lifecycle when the defects become apparent, holding facility managers responsible for defects (Tay & Ooi, 2001) is highly debatable

There is no centralised defect database where facility managers can provide feedback to the designers and both can seek solutions for their problems Such knowledge-base using existing

information and awareness of designers can prevent defective designs This lack of knowledge or information, unawareness, wrong assumptions and moreover poor motivation contribute to the decision errors (Andi & Minato, 2003) Consequently many defects recur in every building (Chong, & Low, 2006) Wardhana & Hadipriono (2003) provides a plausible solution by making an updated defect database accessible for public They suggest a web based version is the most effective as it can save time, cost and hassle

1.1.4.2 Dearth of system selection framework

Unlike maintenance, maintainability carries a far fetching effect of decisions made during design stage (Briffet, 1990) That is why the influence of design on the buildings is greater than ever before By preventing or rather ‘design-out’ defects almost half of the maintenance-related problems could be eliminated (Arditi, & Nawakorawit, 1999a & b) Defects especially those due to fundamental design errors can exhibit a chain effect, hinder building performance and impose spiralling cost burdens (Josephson & Hammarlund, 1999; Ilozor, Okoroh & Egbu 2004) Moreover plethora of modern construction materials and techniques pose a challenge to the designers Any erroneous selection of systems can seriously affect the durability, service life, sustainability, cost of repair and refurbishment of the building, and in turn, additional liabilities would be incurred to the building owners Realizing that ‘trial and error approaches are inefficient and impossible’, Aygun (2000) expressed an urgent need for

an analytical model for systematic selection process

Purely design related issues, namely, selection of systems, components and material should be dealt in details Unfortunately the selection is guided by over-emphasized initial cost (Wong

& Li, 2006), which is hardly 25% of the total LCC (Griffin, 1993) and hence judging economic viability of projects by this initial cost may not be the most economical solution Cheaper materials often require more frequent maintenance (Wong, 1993) Even proposal of using LCC (Architectural Institute of Japan, 1995; Bromilow & Pawsey, 1987; Flanagan & Norman, 1987; Griffin, 1993; ISO 15686-5; McDermott, Torrance & Cheesman, 1987) was

highly challenged (Arditi & Messiha, 1996; Fuller & Petersen, 1995; Haasl & Sharp, 1999) as cost greatly depends on operation & maintenance strategy and results can be particularly erroneous due to the attitude of cost-cutting (Shen, Lo & Wong, 1998) Moreover LCC technique requires large amount of data and is not always practical (Louis & Vanier, 2000)

1.1.4.3 Lack of communication

‘Maintenance and design are frequently treated as if the two activities were unconnected…Maintenance sections often appear to be self-contained… [resulting in] risk of undesirable divorce from other related functions’ (LAMSAC, 1981) Maintenance priority has been well researched by Alibaba & Özdeniz (2004); Caccavelli & Genre (2000); Fwa & Chan (1993); Hayashi (2000); Pullen, Attkinson, & Tucker (2000); Reddy, Coskunoglu & Sucur (1994); Shen, & Lo (1999); Spedding, Holmes, & Shen (1995); Shohet (2003) On the other hand tools such as HQAL, BDAS (CIDB, 1999) and CONQUAS 21 (BCA, 2005) can evaluate durability, buildable design and construction quality respectively Unfortunately these two groups are not integrated Consequently, design decisions are based on incomplete knowledge as long-term performance of such decisions are not available (Chong & Low, 2006) The reluctance of various stakeholders to embrace further responsibility and liability to bridge this communication gap is an obstacle in improved maintainability of buildings in Singapore De Silva et al (2004) argue that till date there is no initiative to articulate the need

of informed decision making to set priority keeping aside ‘the lowest cost’ mentality

1.2 Research guideline

In order to obtain a complete understanding of the multifaceted issue of maintainability, the subject was studied from various angles An extensive literature review was conducted on related topics, namely, building elements, associated defects, maintenance, maintainability, holistic building grading systems and their mathematical principles From the identified knowledge gap, the research guideline was formulated in terms of aim, objectives, hypothesis and scope

1.2.1 Knowledge gap

Unlike sustainability studies, there is no holistic model for building maintainability that can predict the future defects so that best strategy to prevent them can be adopted right from the design stage resulting in a highly maintainable building Detailed process of identification of this knowledge gap can be found in Section 2.8

1.2.2 Aim and Objectives

Taking into consideration the above mentioned research problem and dearth of structured information, the focus of this research was set The main aim was to integrate the building systems and stages of building lifecycle so that the maintainability potential of an entire building can be predicted The objectives were:

● Improving the knowledge-base of building systems, associated defects and their analysis

in terms of causes and effects

● Setting benchmark for selection of the best option from existing design, construction and

maintenance strategy by linking them logically through their influence on building maintainability

● Integration of building elements into COMASS (Comprehensive Maintainability Scoring

System) based on maintainability parameters and making it easily accessible via internet

1.2.3 Hypothesis

● A logical framework can assess and integrate various building elements in terms of

maintainability

● It is possible to identify future defects and predict maintainability potential of both new

and existing building

1.2.4 Scope of Research

As discussed earlier, commercial building sector in Singapore is the most vulnerable in terms

of maintainability Hence for this research, commercial buildings were selected as subject

Office, shopping malls, hotels, business park and community centres belong to this category (SS 499) The major building elements and services under the supervision of central facility management of a typical commercial building were studied These elements were designated

as sub-systems and were grouped under two main systems, as follows:

● Civil- architectural /C&A: (1) basement; (2) facade: (3) wet area and (4) roof

● Mechanical-electrical/M&E: (5) sanitary-plumbing; (6) HVAC/ heating, ventilation,

air-conditioning; (7)elevator; (8) electrical and (9) fire protection

Regarding the aspect of maintainability, the existing concepts were first explored Moua and Russell (2001) have delineated maintainability as a design parameter pertaining to the ease of maintenance It is a formal and structured method to incorporate maintenance knowledge and experience into the delivery process for a new or retrofit project Blanchard, Verma & Peterson (1995) extended this concept up to construction / installation and operation Koo (2000) has mentioned that Singapore’s construction industry requires to introduce practices and methods in the design, construction and maintenance of buildings Hence maintainability was conceived as a structured programme to cover design, construction and maintenance – all three phases of building life cycle The exact scope of each word is explained as follows

● Design: COMASS is a decision enhancement tool to make a designer aware of the

practical implication of his decisions Its design guidelines connect the existing codes or standards to the defects which may occur upon violation of such rules

● Construction: Various building components and materials have their own construction

and installation methods The specific guidelines are exclusively tested and proposed by the manufacturer COMASS deals with the generic guidelines and highlights the result of

a wrong decision For example, it is recommended to use sealant within its shelf life, but exact value of shelf life for a particular product should be obtained from manufacturer

● Maintenance: Here maintenance means regular cleaning, inspection, servicing and minor

fault rectification It is difficult to include responsive maintenance, planned repair or

replacement as part of preventive policy for every item that may go wrong or wear out (Audit Commission, 1988) A planned inspection is the credible solution (Chanter & Swallow, 2007) Hence major repair and replacement were excluded

It should be noted that the aim of the proposed framework was neither to replace existing guidelines, codes or standards by providing new techniques nor to function as a stand-alone design-construction-maintenance encyclopaedia A better clarification in terms of contributions of this research is noted in the following sections

1.2.5 Knowledge Contribution

This research was intended to develop the logical framework for evaluating maintenance potential of a new or existing building so that decisions can be taken at the earliest possible stage for a better result By establishing the missing link between cause and effect of building defects, an effort was made to improve the prime aspects of maintainability The idea was to search for integrated solution for all major building components and explore if there is a new definition of maintainability in today’s context that can create a platform for future research

rudimentary outcome of ‘pass-fail’, focus was cast on pinpointing the drawbacks and overcoming the dangerous folly of ‘point-hunting’ It was planned to be published on the official website of NUS Building Maintainability Research Group (www.hpbc.bdg.nus.edu.sg)

1.3 Definition of terms

Following terms are used throughout this thesis In the present context, the explanations are:

● Maintenance: work undertaken in order to keep, restore, or improve every part of the

building, its services and surrounds, to currently accepted standards, and to sustain the utility and value of the building (CIB, 1990)

● Maintainability: the ability of an item, under conditions of use, to be retained in,

restored to a state in which it can perform its required functions, when maintenance is performed under stated conditions and using prescribed procedures and resources (BS 3811)

● Defects: the results of failures or shortcomings in the function, performance, statutory, or

user requirements of the structure, fabric, services, or other facilities (Low & Wee, 2001) They hinder building performance and incur cost burdens (Chew, Tan & Kang, 2004)

● Performance: the behaviour of a product in use (BS 5240-1) It is related to a building’s

ability to contribute to the fulfilment of its intended functions (Clift and Butler, 1995)

● Criticality: It is a combination of severity of an effect and the probability or expected

frequency of its occurrence When associated with, for example failure mode, the criticality of the effect is called the criticality of the failure mode (BS 5760-5)

1.4 Organisation of the thesis

This thesis has been organised according to the logical development that has taken place over the entire period of research

Chapter 1 Introduction: It presents a brief overview of the concepts of building

maintainability and its importance especially in tropical climate of Singapore Co-existence of abundance of good guidelines and building defects is paradoxical and demands a probing investigation It sets the research question Next the aim, objectives and hypothesis as developed from identified knowledge gap are presented Finally the scope of research and expected contributions to academia and industry are outlined

Chapter 2 Literature review: To obtain a holistic idea of the research problem, the relevant

topics reviewed are: building components, associated defects, priority setting in maintenance, maintainability in buildings and in general, holistic building grading systems and their mathematical background of MCDA principles It helped to recognize the knowledge gap

Chapter 3 Research methodology: Continual development of the entire research framework

is provided The principles for assessing common defects pertaining to nine major building elements (called subsystems) are derived After developing the scoring principles, those subsystems are integrated with respect to objective and subjective parameters Next the validation, sensitivity and application issues are addressed

Chapter 4 Defect analysis: Defects and analysis of their causes and effects are presented

along with pictures The collation is named as Defect Library Statistical analysis of survey data short-listed the critical defects Using FMECA principles, their criticality i.e effect on maintainability is derived This information is used in next stage of research to form the foundation of scoring systems

Chapter 5 Maintainability Handbook: Each of the building subsystems is divided into

major components The factors related to their design, construction and maintenance are used

to develop a comprehensive guideline called Maintainability Handbook Each factor is

assigned with a score of 1 to 5 where 5 is the best practice and 1 is the worst Relative weights

of these factors are determined from the criticality of the defects they can mitigate

Chapter 6 Comprehensive Maintainability Scoring System (COMASS): analysis of the

objective and subjective parameters of building maintainability along with the relative importance of nine major sub-systems are carried out using AHP The objective results are compared and synchronised with the subjective judgements Theoretical implication of inconsistency in AHP decision making is reviewed in the field of building maintainability

Chapter 7 Testing and application: The validity, sensitivity and predictive accuracy of

proposed scoring system is tested as per principles developed in research methodology The whole scoring process, application of logic and computations are demonstrated through a hypothetical commercial office tower The web-based application of COMASS as well as the justification of its efficiency as holistic scoring system is described

Chapter 8 Conclusions: After summarizing the whole research and the key findings, the

conclusions are made Achievement of objectives and precision of hypothesis are addressed After the knowledge contribution and practical implications of this study are highlighted, finally the limitations are discussed, followed by identification of the scope of future research

of key terms and a chapter-wise overview of this report was presented

Chapter 2 Literature Review 2.1 Introduction

This chapter presents a review of the existing body of background knowledge relevant to the research area The multifaceted issue of maintainability was studied from various angles in order to get a complete grasp The whole work was divided into following themes:

● Building elements and associated defects

● Maintenance and maintainability

● Building grading systems and their mathematical principles

First of all the major building elements discussed in the defect or maintenance related studies were scrutinized The causes and consequences of these defects were studied in details along with the guidelines to prevent them Interestingly this first section of literature review continued till the later phases of research, namely, development of Defect Library (Chapter 4) and Maintainability Handbook (Chapter 5) More than 400 books, articles, codes and standards were referred in these two sections For a better organization of the thesis, the knowledge elicited has been merged in subsequent chapters In one sentence, faulty design, construction, maintenance as well as poor coordination among various disciplines were found responsible for building defects

In second section, general research done on both maintenance and maintainability prediction was scrutinized Though maintainability is a design attribute and conceptually opposite to maintenance, but review of maintenance literature is essential These two elements are inseparable because effectiveness of maintainability is reflected only during maintenance Dearth of research in building maintainability led this review to the well-researched area of maintainability studies in system engineering where actually the maintainability concept germinated a century ago Finally the holistic models for building grading systems were

studied Though most of them focus on sustainability, their mathematical principles involving multi criteria decision analysis (MCDA) was considered important for this research

2.2 Building components in terms of maintainability

Building systems that require maintainability approach are highlighted by previous studies related to building defects (Arditi & Nawakorawit, 1999a; BCA, 2000; Chew & Egodgae, 2003; Chew, De Silva & Tan, 2003; Chew & De Silva 2004; Chong & Low, 2006; CIBSE, 2000) and works addressing maintenance priority (Section 2.3) Briefly, these elements are: structure, exterior envelope (wall and window), roof, interior finishing (ceiling, floor, and door), basement, wet area, mechanical-electrical systems (elevators, electrical, HVAC, fire protection, sanitary-plumbing) and others (telecommunication and external work such as landscaping) From the maintainability point of view, building components that fall within the scope of this research (Section 1.2.3) can be classified as nine subsystems grouped under two major systems, namely, civil-architectural (C&A) and mechanical-electrical (M&E) based on their general properties (Table 2.1) Each of these nine subsystems can be further divided into components and sub-components (SS CP 97 Part 1 & 2) as illustrated in Fig 2.1

Table 2.1 Difference between C&A and M&E systems

Design focus Energy efficiency, aesthetics,

spatial performance Energy efficiency, controls, interchangeability (plug & play) Construction Mostly constructed at site Mainly factory assembled and tested unit but

installed and commissioned at site Maintenance

trait Cleaning, repair, replacement Cleaning, repair, replacement, servicing (lubrication, adjustment, calibration, testing) Maintenance

Replacement Difficult, less frequent, sometimes

impossible E.g basement water proofing Elements & building have almost same service life

Easier – standard units are available More frequent

Detection of

defect (visual)

Usually have visible signs E.g

crack, leakage, stain

Usually no visible sign E.g Shock, noise, vibration, over-heating etc

Automatic fault

detection Difficult Easy Integration with BAS is more synchronized

Based on: AMCP 706-133; Chanter & Swallow (2007); CIBSE (2000); Holm (2000); Lee &

Wordsworth (2001); Wani & Gandhi (1999)

Building

− Detector & alarm

− Fire hydrant &

− Cooling tower

− Air distr &

− Finishes

− Sanitary plumbing units

− Water proofing

− Insulation

− Protective finishes

Note: sub-components are not shown, but discussed in Chapter 4 and 5

Fig 2.1 Elements of a building

2.3 Building maintenance

to meet higher standards by employing cutting-edge

y in case of failure This

Modern buildings are designed

technologies and innovative materials Hence the sophisticated and complex buildings are expensive to maintain and repair Maintenance should be planned and managed strategically just like any other corporate activities instead of carrying it out in a purely reactive manner (Arditi et al.,1999a) Ben-Daya, Duffuaa, and Raouf (2000) have classified maintenance strategies into three categories:

● Breakdown maintenance: Replacement or repair is done onl

method is suitable when the hazard rate is constant and its effect is negligible

Preventive maintenance (PM): Performed on a scheduled basis with a scheduled

interval Planning is based on manufacturer’s recommendation or past experience

Condition-based maintenance (CBM): Decisions are based on current condition

component, hence avoiding wastage of resources and performing maintenance activities only when they are needed CBM should be supported by strong condition-monitoring techniques

1 Objectiv

The objective of maintenance manag

applies to buildings or equipments The main aim is to ensure (Corder, 1976):

● Optimum availability of installed equipment to maximize the return on inve

● Proper functioning of the services or equipment

● Safety of the occupants and maintenance personn

● Customer satisfaction

● Enhanced useful life of

2.3.2 Decision support frameworks in maintenance

Continuous increase in maintenance needs and simultaneous decrease in resources have necessitated the process of maintenance priority setting with main aim to determine relative importance of maintenance requirements on the basis of predefined criteria Principles of operational research and management science have been employed in recent years for this purpose A few of major decision support frameworks for maintenance are discussed briefly

● Multi-attribute prioritization model

Developed by Spedding, Holmes & Shen (1995) to set maintenance priorities and was based

on a comprehensive study on several projects run by local authorities in England and Wales Six criteria were selected for grading namely, building status, physical condition, importance

of usage, effects on user, effects on fabrics and effects on service provision Projects were ranked in a relative scale in descending order of total project score Users can select the prioritization process and weighting of various criteria Any work j was given a score of Sji in relation to criteria Ci with relative weight (RW) as Wi The priority index (or overall score) Sj

for work j can be calculated as:

)(

● Point Accumulation System

Shen and Lo (1999) proposed this method to rank a large number of buildings according to their renovation priority score derived through AHP The score is a sum of individual scales assigned for three criteria: (1) the building’s physical state; (2) the importance of the

building’s function and (3) the influence exerted by its users The scale for each criterion depends on the criteria’s relative importance assigned by the evaluator For example, if the scale for the physical state of the building and users’ influence are 1 to 10, and 1 to 5 respectively, the weight of former is double than that of the latter

● Neural Network System

Fwa and Chan (1993) demonstrated that neural networks can be trained to learn various linear functions for priority setting and was applied in traffic maintenance projects The number of data points depends on complexity of the project and the usual range is 5000 to 100000 For most cases, this method cannot be easily implemented due to less number of available data

● RENMOD (Renovation Decision-Support Model)

It was designed to measure functional condition of a military facility and set the renovation priority based on (1) physical parameters; (2) functional parameters, such as geometry, safety, and system compatibility and (3) facility location and peripheral infrastructure (Reddy, Socur

& Ariarathnam, 1993) Functional condition index (FCI) of a facility with numbers of components can be calculated stepwise as:

Where X(i) = the condition of component i

W(i) = the relative weight (RW) of that component within the overall functional condition

Xk(i) = the condition of subcomponent k of component i

and Wk(i) = the RW of subcomponent k in terms of component i

In this manner RENMOD can be split further into deep hierarchy and lowest level components are judged first The conditions were graded in scale of 1-10 against fixed criteria and RWs were determined by AHP

● Maintenance performance indicators

For hospitality buildings with sensitive user requirements and high expectations, Chan, Lee and Burnett (2001) proposed these indicators, namely, business availability, manpower utilization index, urgent repair request index, preventive maintenance ratio, energy user index and failure frequency & unit repairing time A building is judged against predefined standards w.r.t these indicators

● Building performance indicator (BPI)

For condition based maintenance, BPI was proposed for 10 major building systems and was calculated using the following equation (Shohet, 2003) Individual grading was done in a 5- point scale and later converted into 100 point scale

∑ =

= 10n 1PnWn

Where P = performance level of a system in 1-100 scale It is the weighted sum of (1) the

system’s physical state, (2) typical failures or defects and (3) preventive maintenance

maintenance cost or LCC for its components to the LCC of the whole building

W

● KPIs for integrated maintenance management

Proposed by Shohet, Lavy-leibovich & Bar-on (2003), the four key performance indicators (KPI) were, namely: (1) BPI as mentioned earlier to express building’s physical-functional condition; (2) Manpower Sources Diagram or MSD to represent labour composition (in-house

vs outsourcing); (3) Maintenance Efficiency Indicator or MEI for cost effectiveness and (4) Managerial Span of Control or MSC to reflect organizational effectiveness as the ratio between the managers and the respective number of direct subordinates

● Resource allocation in rehabilitation projects

Shohet et al (2004) allocated resources for rehabilitation projects through (1) elimination of unfeasible solutions and (2) identification of near optimum solution based on: initial investment, performance level, project duration, annual maintenance costs and economic life

cycle Their aim was to maximize benefits keeping the budget fixed or minimize costs while keeping the performance constant Performance of 10 major building systems was graded on

a scale from 1 to 5 where 1 is dangerous and 5 is very good

● Fuzzy expert system

Chang and Ibbs (1990) employed users’ opinion to grade: (1) the probability of occurrence of the event that represents the priority setting criterion and (2) the activities to which resources are to be allocated, namely, personnel, equipment and logistics Accuracy of this method is highly dependent on subjective opinion

● ILS based maintenance strategy

El-Haram and Horner (2003) used integrated logistics support (ILS) concepts to integrate physical and functional models of a building Failure Mode Effects Analysis (FMEA) and Reliability Centred Maintenance (RCM) were used to express the impacts of defects on health, safety, economy, operation and appearance to achieve a cost effective maintenance

● Multi-criteria composite index model

It is an experimental model developed by Cook and Kress (1994) A number of alternatives were assessed and each was given a final score based on a weighted addition of ordinal and cardinal criteria or combining incomparable criteria as cost and time

● Other examples

Hayashi (2000) used five parameters for building and maintenance evaluation, in which the extent of planned maintenance activities actually carried out, got the highest ranking (0.4 out

of 1.0) Caccavelli and Genre (2000) summarized the current state of a building, cost estimate

of various works and refurbishment needs with respect to energy conservation The model consists of 50 elements grouped into six types and ranked according to four codes namely, a – good state; b – slight degradation; c – medium degradation; and d – poor state requiring replacement

Allehaux and Tessier (2002) determined functional obsolescence of electro-mechanical systems in office buildings through 3-tier quality criteria Guidelines were given to improve any element with lower grade Pullen et al (2000) defined seven KPIs for the evaluation of maintenance departments of Australian hospitals These indicators were mainly business-oriented rather than related to physical performances

2.4 Maintainability

Unlike maintenance, maintainability is an inherent characteristic of design and contributes to the ease, accuracy, safety and economy during maintenance period But this concept is not limited only to design or maintenance, it covers construction or installation and operation of the facility A good design might not remain maintainable if installed or operated badly (Blanchard & Lowery, 1969)

2.4.1 Objectives of maintainability

● Reduce amount, frequency and complexity of maintenance and hence reduce LCC

● Reduce mean time to repair and amount of supply supports

● Determine extent of preventive maintenance to be performed

● Provide maximum scope for interchange i.e consideration of modular replacement vs

part repair or throw-away design This is more applicable to systems and equipments (Dhillon, 1983)

2.4.2 Maintainability in building research

Maintainability has not been studied in great details except by Building Maintainability Research Group of National University of Singapore Maintainability Scoring System (MSS) for quantitative building evaluation was developed for improving the knowledge of maintainability and setting industry benchmarks A defect list for facade and wet area collated through field studies and interviews was graded by four factors, namely, (1) ease of rectification; (2) impact on performance; (3) tendency to aggravate and (4) tendency to result