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THE CONSULTANCY FEE FOR STRUCTURAL DESIGN CHANGES OF
REINFORCED CONCRETE BUILDINGS IN OMAN
AMUR SALIM HAMOOD AL-HARTHY
UNIVERSITI TEKNOLOGI MALAYSIA
THE CONSULTANCY FEE FOR STRUCTURAL DESIGN CHANGES OF
REINFORCED CONCRETE BUILDINGS IN OMAN
AMUR SALIM HAMOOD AL-HARTHY
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Doctor of Philosophy
Faculty of Civil Engineering
Universiti Teknologi Malaysia
MARCH 2006
ABSTRACT
Design changes in reinforced concrete buildings have for long time been a topic of prolonged arguments and frequent disputes due to their common phenomena of incidents in the construction industry. Although design changes in many cases are essential, clients, consulting engineers and contractors all have become increasingly worried about the negative parts that are associated with them. Design changes do not only affect the reliability of design but also increase the possibility of contractual disputes due to unpredictable delay and cost overrun on the original scope of work. While the cost of modifying the construction scopes is well defined in normal contract documents, but the fee of engineering changes is yet to receive more attention. Therefore this research has been developed with the aim to investigate such issues and to develop an alternative approach in evaluating the fee of altering the original scope of design work. Extensive study was performed at the initial stage of this research work in term of interviews, case studies and questionnaire survey in order to identify the sources, causes and impacts of design changes on reinforced concrete buildings as well as to establish corrective actions and preventive measures to minimise the avoidable ones. Frequency analysis and non-parametric statistical technique employed in this research to analyse the qualitative and quantitative data. It was found that engineering design changes are common in the industry and, in many cases, lead to excessive claims and disputes due to lack of appropriate and practical methods to assess their associated fee. Although there are various methods being used for assessing the fee of design changes, this study identified their limitations for practical use. Consequently, an alternative method for assessing the fee of the structural design changes has been developed in this research based on designing various type and complexity of low rise RC buildings. The developed method has been verified by a panel of experts by means of questionnaire survey and found to be practical, suitable and effective. Set of guidelines for improving consultancy design documents with respect to design changes and another set of guidelines for managing their claims have been also developed. These guidelines have been validated by panel of experts using Delphi technique. The result of the validation process provides encouragement to recommend the guidelines for practical implementation.
ABSTRAK
Perubahan terhadap rekabentuk asal bagi pembinaan bangunan konkrit bertetulang (RC) sering berlaku dan isu ini telah sekian lama diperbahaskan. Ia juga sering menjadi punca perbalahan dalam industri pembinaan. Walaupun perubahan dalam rekabentuk dalam keadaan tertentu adalah perlu dilakukan tetapi kesan negatif akibat daripada perubahan yang dibuat juga turut mebimbangkan pihak yang terlibat seperti klien, jurutera perunding dan kontraktor. Perubahan terhadap rekabentuk bukan sahaja meninggalkan kesan terhadap kredebilitinya rekabentuk itu sendiri malah boleh mendorong kepada berlakunya perbalahan kontrak disebabkan oleh kelewatan kerja dan perubahan kos akibat daripada perubahan daripada skop asal kerja. Lazimnya kaedah penilain terhadap perubahan kos bagi kerja pembinaan akibat daripada perubahan skop kerja agak jelas mengikut peruntukan yang sedia ada didalam kontrak pembinaan. Walaubagaimana pun kaedah penialaian kos terhadap perubahan bagi kerja merebentuk tidak begitu mendapat perhatian para penyelidik. Oleh itu kajian ini telah dijalankan untuk mengenalpasti masaalah ini dengan lebih mendalam serta mengemukakan suatu kaedah alternatif bagi menilai kos perubahan bagi mengubahsuai rekabentuk asal yang dilaksanakan oleh pihak perunding. Pada peringkat awal kajian ini tela mengenalpasti punca, kesan dan kaedah penialain kos dalam proses membuat perubahan terhadap rekabentuk bagi sesabuah bangunan konkrit. Juga dikaji adalah kaedah yang boleh digunakan untuk mengurangkan keperluan membuat prubahan rekabentuk oleh pihak klien. Kaedah penyelidikan yang digunakan termasuklah sesi temubual, kajian kes dan menghantar borang soal selidik kepada responden. Kaedah analisa frekuensi dan kaedas Statistik Tak Berparametar telah digunakan untuk membuat analisa data kualitatif dan kuantitatif yang digunakan dalam penyelidikan ini. Hasil dari kajian mendapati bahawa perubahan terhadap rekabentuk adalah sesuatu yang lazim berlaku dan dalam banyak kes menyebabkan berlakunya tuntutan tambahan yang berlebihan yang dibuat oleh perunding akibat daripada tidak ada kaedah yang sesuai untuk membuat penialaian kos yang praktikal dan wajar digunakan. Lanjutan dari itu hasil dari penyelidikan ini telah membangunkan satu kaedah yang sesuai digunakan untuk sebagai kaedah alternatif untuk membuat penialaian apabila berlakunya perubahan atau pengubahsuaian terhadap rekabentuk asal terhadap struktur bangunan konkrit bertetulang sederhana tinggi. Kaedah ini telah dipersetujui sebagai sesuai digunakan oleh panel para professional yang mempunyai pengalaman yang luas dalam industri pembinaan di Oman. Selain dari itu penyelidikan ini turut membangunkan satu garispanduan yang sesuai diterapkan dalam kontrak untuk mengemaskini lagi proses membuat perubahan rekabentuk dan menguruskan tuntutan yang dibuat berkaitan dengan perubahan yang dibuat tersebut. Garispanduan ini telah dibuat pengesahan dengan panel yang berpengalaman dalam industri pembinaan di Oman dengan menggunakan kaedah Delphi.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION OF THE STATUS OF THESIS
SUPERVISORS' DECLARATIONS
TITLE PAGE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xiv
LIST OF FIGURES xix
LIST OF SYMBOLS xxii
LIST OF APPENDICES xxiii
1 INTRODUCTION 1
1.1 Background and Rationale 1
1.2 Problem Statement 4
1.3 Aim and Objectives 5
1.4 Scope and Limitations of the Research 6
1.5 Brief Research Methodology 7
1.6 Justification of the Research 7
1.7 Significance of the Study 10
1.8 Research Contributions 10
1.9 Organization of the Thesis 10
viii
2 DESIGN CHANGES 14
2.1 Introduction 14
2.2 Definitions of Design Changes 14
2.3 Classifications of Design Changes 15
2.4 Sources of Design Changes 17
2.5 Causes of Design Changes 20
2.6 Impact of Design Changes 28
2.6.1 Impact of Design Changes on Cost 31
2.6.2 Impact of Design Changes on Time 34
2.6.3 Impact of Design Changes on Productivity 36
2.7 Development for Improving the Management of 41 Design Changes
2.8 Chapter Summary 45
3 THE PRINCIPLE OF CONSULTING 48 ENGINEERING PRACTICE
3.1 Introduction 48
3.2 Definition of the Client 49
3.3 Definition of the Consulting Engineer 49
3.4 Reasons for Consulting Engineering Services 50
3.5 Services Provided by Consulting Engineers 52
3.5.1 Feasibility Study Phase 53
3.5.2 Preliminary Design Phase 53
3.5.3 Detailed Design Phase 54
3.5.4 Tender Stage 54
3.5.5 Supervision Phase 55
3.5.6 Operation Phase 56
3.6 Methods of Charging for Consulting Services 57
3.6.1 Lump Sum Method 58
3.6.2 Salary Cost Times Multiplier Plus 59 Non-Salary Cost method
3.6.3 Cost plus Fixed Amount Method 59
3.6.4 Per Diem Method 60
3.6.5 Percentage of Construction Cost 61
3.6.6 Retainer Method 64
ix
3.7 Chapter Summary 64
4 THE CONSTRUCTION INDUSTRY IN OMAN 66
4.1 Introduction 66
4.2 Oman at a Glance 67
4.3 Brief Highlights on Oman Economy 67
4.4 The Construction Sector in Oman 68
4.5 Consulting Engineering Services in Oman 71
4.6 Typical Scope of Consultant Services in 71 Omani Standards
4.7 Fee Assessment of the Design Changes in 75 Omani Standard
4.8 Chapter Summary 76
5 RESEARCH METHODOLOGY 78
5.1 Introduction 78
5.2 Literature Review 79
5.3 Interviews with Professionals 80
5.4 Case Studies 81
5.5 Questionnaire Survey 82
5.5.1 Design of the Questionnaire 83
5.5.2 Pilot Survey 85
5.5.3 Main Survey Questionnaire 85
5.5.4 The Population and the Distribution of the 86 Questionnaire Survey
5.5.5 Methods of Analysing the Questionnaire Survey 88
5.6 Methodology for Development of an Alternative 92 Method to Assess the Fee of Structural Design Changes
5.6.1 Design Parameters and Assumption for the 95 Building Design
5.6.2 Details and Classifications of the 95 Selected Buildings
5.6.3 Source of the Structural Design of the Buildings 96
5.6.4 General Structural System for the 97 Buildings of this Study
x
5.6.5 The Principle of the Adopted Structural Design 97
5.7 Questionnaire for Validating the Developed Method 99
5.7.1 Design of the Questionnaire 99
5.8 Development of the Guidelines 100
5.9 The Method of Validating the Developed Guidelines 102
5.9.1 Background of the Delphi Method 102
5.9.2 Selection of the Professionals for the 104 Delphi Questionnaires
5.9.3 Identifying the Number of Professionals for the 105 Delphi Method
5.9.4 Identifying the Number of Rounds for the 105 Delphi Method
5.9.5 Format of the Delphi Rounds for this Research 106
5.10 Chapter Summary 106
6 DATA COLLECTION 108
6.1 Introduction 108
6.2 Interviews with Professionals 109
6.2.1 Discussions of the Interviews’ Results 109
6.2.2 The Occurrence of Design Changes 109
6.2.3 The Causes and Sources of Design Changes 118
6.2.4 The Impact of Design Changes 119
6.2.5 Existing Methods for Assessing the Fee of 119 Design Changes and their Limitations
6.3 Case Studies Results 121
6.3.1 Case Study One 121
6.3.2 Case Study Two 123
6.3.3 Case Study Three 125
6.3.4 Causes of Design Changes 126
6.3.5 Sources of Design Changes 128
6.3.6 Impact of Design Changes on Cost 129
6.3.7 Impact of Design Change on Schedule 130
6.3.8 Existing Methods for Assessing the 131 Structural Design Changes
6.4 Questionnaire Survey Result 132
xi
6.4.1 Causes of Design Change Due to Clients 132
6.4.2 Causes of Design Change Due to Consultants 135
6.4.3 Causes of Design Change Due to Contractors 137
6.4.4 Sources of Design Changes 139
6.4.5 Impacts of Design Change 141
6.4.6 Corrective Actions and Preventive 144 Measures to Minimize the Avoidable
Design Changes
6.4.7 Preferences of Using the Existing 149 Methods for Assessing the Fee of Design Changes
6.4.8 Limitations of the Existing Methods 150
6.4.8.1 Limitations of the Man-Hours Method 151
6.4.8.2 Limitations of the Percentage of 153 Construction Method
6.4.8.3 Limitations of the Area Unit Rate Method 154
6.4.8.4 Limitations of the Lump-Sum Method 157
6.5 Chapter Summary 158
7 DEVELOPMENT OF THE PROPOSED METHOD 160 TO ASSESS THE FEE OF THE STRUCTURAL DESIGN CHANGES IN RC BUIDLINGS
7.1 Introduction 160
7.2 Preliminary Structural Design Phase 161
7.2.1 Locations of the Structural Members 161
7.2.2 Load Calculations 162
7.2.3 Sizing the Structural Members 163
7.2.4 Miscellaneous Structural Elements 166
7.3 Detailed Structural Design Phase 166
7.4 Preliminary Structural Drafting Phase 168
7.5 Detailed Structural Drafting Phase 170
7.6 General Approach for Developing the Proposed Method 170
7.7 Design by Manual Method 172
7.7.1 Preliminary Design and Drafting for 172 One Floor Buildings
xii
7.7.2 Detailed Design and Drafting for 176 One Floor Buildings
7.7.3 Preliminary Design and Drafting for 181 Two Floors Buildings
7.7.4 Detailed Design and Drafting for 185 Two Floors Buildings
7.7.5 Preliminary Design and Drafting for 189 Three Floors Buildings
7.7.6 Detailed Design and Drafting for 194 Three Floors Buildings
7.7.7 Preliminary Design and Drafting for 197 Four Floors Buildings
7.7.8 Detailed Design and Drafting for 202 Four Floors Buildings
7.7.9 Comparison of the Preliminary Design for 205 the Four Types Buildings
7.7.10 Comparison of the Detailed Design for 206 the Four Types Buildings
7.7.11 Comparison between the Preliminary and 208 Detailed Design
7.8 Design Based on STAAD Pro. Software 210
7.8.1 Preliminary Design and Drafting by 211 STAAD Pro for One Floor Buildings
7.8.2 Detailed Design and Drafting by 216 STAAD Pro for One Floor Buildings
7.8.3 Preliminary Design and Drafting by 220 STAAD Pro for Two Floors Buildings
7.8.4 Detailed Design and Drafting by 224 STAAD Pro for Two Floors Buildings
7.9 Suggested Method for Assessing the Fee of the 228 Structural Design Changes
7.10 Illustration for Using the Proposed Method 231
7.10.1 Example 1, One Floor Building 231
7.10.2 Example 2, Two Floors Building 234
7.11 The Result of the Validation 238
7.12 Chapter Summary 240
xiii
8 DEVELOPMENT OF THE GUIDELINES 242 FOR MANAGING DESIGN CHANGES
8.1 Introduction 242
8.2 Initial List of Guidelines for Improving Consultancy 242 Design Documents
8.3 Initial List of Guidelines for Managing the Claims of 245 Design Changes
8.4 Validation of the Developed Guidelines 246
8.5 The Delphi Round One Questionnaire 247
8.5.1 The Result of the Delphi Round One 247 Questionnaire
8.6 The Delphi Round Two Questionnaire 248
8.6.1 The Result of the Delphi Round Two 248 Questionnaire
8.7 The Delphi Round Three Questionnaire 252
8.7.1 The Result of the Delphi Round Three 253 Questionnaire
8.8 Chapter Summary 254
9 CONCLUSIONS AND RECOMMENDATIONS 245
9.1 Introduction 255
9.2 Conclusions 256
9.3 Contributions of the Research 263
9.4 Suggestions for Further Research 263
REFERENCES 265
Appendices A - G 277 - 353
xiv
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Actual Causes of Changes in the UK 18 2.2 Importance Indexes of Sources of 19
Changes in Saudi Arabia 2.3 Sources of Changes, In Botswana, Gabrone 20 2.4 Causes of Changes in Hong Kong Building Projects 24 2.5 Causes of Changes in Botswana 27 2.6 Effects of Changes on Projects 30 2.7 Project Size and Changes Measurer 32 2.8 Causes and Cost of Changes 34 2.9 Quantitative Effect of Disruptions 38 3.1 Converted Building Scale for Structural Works 63 in Buildings Expressed As A % of Building Cost 4.1 No. of Building Permits, Estimated Cost and Type of Building 70 4.2 Consulting Firms Grades 72 5.1 Ranking System for the Questionnaire of this Study 89
using Likert (Ordinal) Scale 5.2 Basic Buildings Details 96 6.1 Result of the Interviews with Consultants 110 6.2 Result of the Interviews with Contractors 112 6.3 Result of the Interviews with Clients 114
xv
6.4 Result of the Interviews – Comparisons of Respondents 116 6.5 Case Study One - Causes, Sources and Fee of Changes 122 6.6 Case Study Two - Causes, Sources and Fee of 124
Design Changes 6.7 Case Study Three - Causes, Sources and Fee of 127
Design Changes 6.8 Case Studies - Impact on Cost 130
6.9 Case Studies - Impact on Schedule 131 6.10 Main Scores (MS) and Ranks (R) for Causes of 133
Design Changes Due to Clients
6.11 Test for Agreement on the Ranking for Causes of 134 Design Changes Due to Clients
6.12 Main Scores (MS) and Ranks (R) for Causes of 136 Design Changes Due to Consultants
6.13 Test for Agreement on the Ranking for Causes of 137 Design Changes Due to Consultants
6.14 Main Scores (MS) and Ranks (R) for Causes of 139 Design Changes Due to Contractors
6.15 Test for Agreement on the Ranking for Causes of 139 Design Changes Due to Contractors
6.16 Main Scores (MS) and Ranks (R) for Sources 140
of Design Changes 6.17 Test for Agreement on the Ranking for Sources 141
of Design Changes 6.18 Main Scores (MS) and Ranks (R) for Impacts 142
of Design Changes 6.19 Test for Agreement on the Ranking for Impacts 143
of Design Changes 6.20 Main Scores (MS) and Ranks (R) for Corrective 145
Actions and Preventive Measures to Minimize the Avoidable Design Changes
xvi
6.21 Test for Agreement on the Ranking for 149 Corrective Actions and/or Preventive Measures to Minimize the Avoidable Design Changes
6.22 Main Scores (MS) and Ranks (R) for Preference 150
of Existing Methods for Assessing the Fee of Design Changes
6.23 Main Scores (MS) and Ranks (R) for 151
Limitation(s) of the Man-Hours Method 6.24 Main Scores (MS) and Ranks (R) for Limitation(s) 153
of the Percentage of Construction Cost Method 6.25 Main Scores (MS) and Ranks (R) for 155
Limitation(s) of the Area Unit Rate Method 6.26 Main Scores (MS) and Ranks (R) for 157
Limitation(s) of the Lump-Sum Method 7.1 Times, in Minutes, and Percentage of Time for 172
Preliminary Structural Design (One Floor Buildings) 7.2 Times, in Minutes, and Percentage of Time for 173 Preliminary Structural Drafting (One Floor Buildings) 7.3 Percentage of Time for Preliminary Structural 174
Design and Drafting (One Floor Buildings) 7.4 Times, in Minutes, and Percentage of Time for 177
Detailed Structural Design (One Floor Buildings) 7.5 Times, in Minutes, and Percentage of Time for 178
Detailed Structural Drafting (One Floor Buildings) 7.6 Percentage of Time for Detailed Structural 179
Design and Drafting (One Floor Buildings) 7.7 Times, in Minutes, and Percentage of Time for 182
Preliminary Structural Design (Two Floors Buildings) 7.8 Times, in Minutes, and Percentage of Time for 183
Preliminary Structural Drafting (Two Floors Buildings) 7.9 Percentage of Time for Preliminary Structural 184 Design and Drafting (Two Floors Buildings) 7.10 Time, in Minutes, and Percentage of Time 186
For Detailed Structural Design (Two Floors Buildings)
xvii
7.11 Time, in Minutes, and Percentage of Time 187 for Detailed Structural Drafting (Two Floors Buildings)
7.12 Percentage of Time for Detailed Structural 188
Design and Drafting (Two Floors Buildings) 7.13 Times, in Minutes, and Percentage of Time for 190
Preliminary Structural Design (Three Floors Buildings) 7.14 Times, in Minutes, and Percentage of Time for 191
Preliminary Structural Drafting (Three Floors Buildings) 7.15 Percentage of Time for Preliminary Structural 192
Design and Drafting (Three Floors Buildings) 7.16 Times, in Minutes, and Percentage of Time for 194 Detailed Structural Design (Three Floors Buildings) 7.17 Times, in Minutes, and Percentage of Time for 195
Detailed Structural Drafting (Three Floors Buildings) 7.18 Percentage of Time for Detailed Structural Design and 196
Drafting (Three Floors Buildings) 7.19 Times, in Minutes, and Percentage of Time for 198
Preliminary Structural Design (Four Floors Buildings) 7.20 Times, in Minutes, and Percentage of Time for 199
Preliminary Structural Drafting (Four Floors Buildings) 7.21 Percentage of Time for Preliminary Structural Design 200
and Drafting (Four Floors Buildings) 7.22 Times, in Minutes, and Percentage of Time for Detailed 202
Structural Design (Four Floors Buildings) 7.23 Times, in Minutes, and Percentage of Time for Detailed 203
Structural Drafting (Four Floors Buildings) 7.24 Percentage of Time for Detailed Structural Design 204
and Drafting (Four Floors Buildings) 7.25 Time, in Minutes, and Percentage of Time for 208
Preliminary and Detailed Structural Design and Drafting 7.26 Times, in Minutes, and Percentage of Time for 212
Preliminary Structural Design based on STAAD Pro Design Software (One Floor Buildings)
xviii
7.27 Percentage of Time for Preliminary Structural Design 213 and Drafting Based on STAAD Pro Design Software (One Floor Buildings)
7.28 Times, in Minutes, and Percentage of Time for Detailed 216
Structural Design based on STAAD Pro Design Software (One Floor Buildings)
7.29 Percentage of Time for Detailed Structural Design 217
and Drafting based on STAAD Pro Design Software (One Floor Buildings)
7.30 Times, in Minutes, and Percentage of Time for Preliminary 220
Structural Design based on STAAD Pro Design Software (Two Floors Buildings)
7.31 Percentage of Time for Preliminary Structural Design 221
and Drafting based on STAAD Pro Design Software (Two Floors Buildings)
7.32 Times, in Minutes, and Percentage of Time for Detailed 224
Structural Design based on STAAD Pro Design Software (Two Floors Buildings)
7.33 Percentage of Time for Detailed Structural Design 225
and Drafting based on STADD Pro Design Software (Two Floors Buildings)
7.34 Percentage of Time for Preliminary Structural Design 229
and Drafting (One Floor to Four Floors Buildings) 7.35 Percentage of Time for Detailed Structural Design 230
and Drafting (One Floor to Four Floors Buildings) 7.36 Questionnaire Result for the Validation of the POF Method 239 8.1 Delphi Round Two Results: Relative Importance 249
Level of each Guideline for Improving the Consultancy Design Documents
8.2 Delphi Round Two Results: Relative Importance 251 Level of each Guideline for the Claims of the Design Changes
xix
LIST OF FIGURES
FIGURE NO. TITLE PAGE 1.1 Research Methodology Flow Chart 8 2.1 Causes of Changes in Hong Kong 25 2.2 Planned and Actual Loading Curves 36 2.3 Effects of Change within Phase 39 2.4 Construction Change and Construction Productivity 39 2.5 Design Change and Design Productivity 40 3.1 Stages in Projects’ Design Cycle 52 3.2 Median Basic Fees as a Percentage of Net 62
Construction Cost 5.1 Type of Organization Represented 87 5.2 Distribution Profiles of Work Experience of the 88
Three Groups of Survey Respondents 7.1 Percentages of Time for the One Floor Buildings 176
at Preliminary Design Stage based on Manual Method 7.2 Percentages of Time for the One Floor Buildings at 181
Detailed Design Stage based on Manual Method 7.3 Percentages of Time for the Two Floors Buildings 185
at Preliminary Design Stage based on Manual Method 7.4 Percentages of Time for the Two Floors Buildings at 189
Detailed Design Stage based on Manual Method 7.5 Comparison between the Estimated Percentages of 193
Time to Design Main Structural Members for the Three Buildings of Three Floors each at Preliminary Design Stage
xx
7.6 Comparison between the Estimated Percentages of 197 Time to Design Main Structural Members for the Three Buildings of Three Floors each at Detailed Design Stage
7.7 Comparison between the Estimated Percentages of Time 201
to Design Main Structural Members for the Three Buildings of Four Floors each at Preliminary Design Stage
7.8 Comparison between the Estimated Percentages of Time 205
to Design Main Structural Members for the Three Buildings of Four Floors each at Detailed Design Stage
7.9 Comparisons between Percentages of Time to Design 206
Main Structural Members for the Four Buildings at Preliminary Design Stage
7.10 Comparisons between Percentages of Time to Design 207
Main Structural Members for the Four Buildings at Detailed Design Stage
7.11 Comparison between Percentages of Time for 209
Preliminary and Detailed Design Stages 7.12 Percentages of Time for the One Floor Buildings at 214
Preliminary Design Stage based on STAAD Pro Design Software
7.13 Comparison between Manual Design Vs. STAAD Pro 215
Design Software for One Floor Buildings at Preliminary Design Stage
7.14 Percentages of Time for the One Floor Buildings 218
at Detailed Design Stage based on STAAD Pro Design Software
7.15 Comparison between Manual Design Vs. STAAD Pro 219
Design Software for the Three Buildings of One Floor each at Detailed Design Stage
7.16 Percentages of Time for the Two Floors each 222
at Preliminary Design Stage based on STAAD Pro Design Software
7.17 Comparison between Manual Design Vs. STAAD Pro 223
Design Software for the Three Buildings of Two Floors each at Preliminary Design Stage
7.18 Percentages of Time for the Two Floors Buildings 226
at Detailed Design Stage based on STAAD Pro Design Software
xxi
7.19 Comparison between Manual Design Vs. STAAD Pro 227 Design Software for the Three Buildings of Two Floors each at Detailed Design Stage
7.20 Original Plinth (Ground) Beams Plan 232 7.21 Modified Plinth (Ground) Beams Plan 232 7.22 Original Roof Slabs/Beams Plan 233 7.23 Modified Roof Slabs/Beams Plan 233 7.24 Original Ground Floor Roof Slabs/Beams Plan 235 7.25 Modified Ground Floor Roof Slabs/Beams Plan 235 7.26 Original First Floor Roof Slabs/Beams Plan 236 7.27 Modified First Floor Roof Slabs/Beams Plan 236
xxii
LIST OF SYMBOLS
di - The different between the rank given by one group and the rank given by another group f - frequency of responses to each score for each factor fn - Total number of factors ranked by any two groups for any given category OCC - Original Contract Fee MS - Mean Score N - Number of responses Nf - total number of responses NMM - Number of the Modified structural Members TNM - Total Number of the structural Members S - Score given to each factor as ranked by the respondents
xxiii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Extract from Standard Form of Agreement and 277 Conditions for Consultancy Services for Building and Civil Engineering Works (1987)
B Questionnaire Survey – Second Stage 284 C Architectural Plans and Elevations 296 D Typical Structural Design and Detail 321 E Questionnaire for Validating the POF Method 330 F Round One Delphi Questionnaire Survey 340 G Round Three Delphi Questionnaire Survey 346
CHAPTER 1
INTRODUCTION
1.1 Background and Rationale
Engineering design changes and their consultancy design fee assessment for
reinforced concrete buildings’ design have, for long time, been a topic of prolonged
discussions and frequent disputes between clients and their appointed consulting
engineers. Design changes in their simple term are defined as any addition, omission
or modification to the original scope of work in which a contract was signed
(Akinsola et al., 1997) or an adjustment to the completed design that may leads to
change the original contract design fee (Baxendale and Schofield, 1996). These
design changes might have great effect especially on cost and time and are likely to
be a cause of claims and disruptions. In general, consulting engineers provide the
necessary effort to develop the concept of the design to fulfil the intended use of the
projects under design to their client’s requirements. An approval to preliminary
design principle sets the basis for subsequent detailed design and for production of
technical specification and construction documents.
It is common in the construction industry for almost all projects to go through
various degrees of modifications at the design stage and more commonly during the
construction. These changes are mostly caused by clients, in favour of getting new
ideas or cost reduction on projects (Federal Construction Council, 1983; Kelvin,
1996). Design members have been also the main contributors of the design changes
in the construction industry. They originate the changes to rectify their mistakes and
2
to improve or optimize their design (Hibberd, 1982; Choy and Sidwell, 1991).
Contractors may also introduce changes to adopt alternative construction methods
that are of more familiarity (McDermott and Dodd, 1984; Yogeswaran, 1998) and
suppliers, in order to meet the manufacturer’s recommendation to use a specific
material (Emmitt, 2001).
The most common reasons that necessitate design changes are financial
(Ssegawa, et al. 2003), clients’ new requirements (Wilson, 1982), coordination
problems (Bubshait et al., 1998), unclear scope of work (Austin et al., 2002), design
errors (Leonard, et al., 1988), unexpected site conditions (Essex, 1996) and
insufficient design information at the design stage (Ogunlana, et al., 1996). The
possible changes could be minor related to design development which have no or
relatively low cost effect on overall agreed design fees and could be major related to
new ideas or changing the principle of the original design which, in turn, required re-
planning and re-designing that leads to a major cost effect.
There are numerous impact caused by design changes that influence the
outcome of a project. Any inferior assessment, determination, misunderstanding or
unavailability of relevant information or knowledge during the design stage leads
inevitably to less than an optimum design that can be unnecessarily expensive and
difficult to correct/alter at later stages of a project life cycle (Hashimoto, 1993). A
successful project means that the project has met the required quality level,
completed on time and within the allocated budget (Chan and Kumaraswamy, 1994;
Frimpong et al. 2003). Design changes usually divert these fundamental aims in the
construction industry. These changes lead to great disruption on design and
construction activities which, in turn, increase the chances for errors, increase cost,
delay and decrease productivity.
Although design changes in many cases are essential for, as example, design
development; clients, consulting engineers and contractors all have become
increasingly worried about their magnitude and their impact that are associated with
them. Design changes do not only affect the reliability of the design but also
increase the possibility of contractual disputes due to the unpredictable delay and
cost overrun on the original scope of work. The three case studies that have been
3
carried out from the construction industry in the Sultanate of Oman and were part of
this research investigation have shown that the engineering consultancy fee can be as
high as 189.8 percent of the original fee and the engineering consultancy time can
increase by 195 percent.
While the cost of modifying the construction scopes is well defined in normal
contract documents, the fee of engineering changes is yet to receive more attention.
Clients are not always willing to accept the variation charges set by consulting
engineers mainly because they feel they are unjustifiable and consultants, on the
other hand, feel that clients unreasonably reject or reduce the claimed amount. This
can be predicted to some extend since the design changes are not easily quantified.
They are various methods in which consulting engineers have been using to
assess the consultancy design fee associated with design changes These methods
have been identified from the result of the interviews with the professionals working
in the construction industry, from the case studies and from the questionnaire that all
were carried out at the initial stage for this research work. These methods are the
Man-Hours method, Percentage of Construction Cost method, Area Unit Rate
method and the Lump-Sun method. However the result of the interviews with the
professionals working in the construction industry; the case studies; and the
questionnaire survey that have been conducted as part of this research revealed that
each one of these methods has various degrees of difficulties and limitations for
implementation to the point where it becomes unpractical to adopt anyone of them.
To avoid the possible disputes arising from the lack of an affective way to evaluate
the engineering consultancy fee of design changes, there is a need to develop a
practical method for fee assessment of the structural design changes when they arise.
The primary aim of this research work is to develop an alternative method for
assessing the consultancy design fee as a result of modifying the original structural
design; to highlight suggestions for minimizing the avoidable design changes; and to
provide guidelines for improving the consultancy design documents with respect of
managing design changes
4
1.2 Problem Statement
Many articles have been written on the general subject of design changes.
Much of that research have focused on their nature and extend such as causes,
sources and impacts, where others have concentrated on their legal aspects such as
claims and disputes. Although design changes in many cases are essential for, as
examples, design developments, design improvements, rectification of mistakes and
resolution of problems related to unexpected circumstances, nevertheless, clients,
consulting engineers and contractors all have become increasingly worried about the
negative parts that are associated with design changes, and the poor recovery of the
actual fee associated with their settlements (Jergeas and Hartman, 1994).
Nevertheless, design changes are still an ongoing problem that continues to raise the
concerns in the construction industry. Such concerns stimulated this research and
others to produce a series of reports, for example Latham report (1994) where
variations have been identified as one of the main problems challenging the
construction industry.
Almost all projects go through different level of modifications not only at the
design stage but also during the construction. Previous studies such as the one by
Anderson and Tucker (1994) reveals that about one third of architectural/engineering
projects missed cost and schedule targets as a result of design changes. Burati et al.
(1992) have shown that design changes increased the construction cost by an average
amount of 12.4 percent of the total cost of the projects in the United Kingdom.
Chang (2002) reported that an engineering consultancy fee increased on an average
of 24.8 percent based on four sampled projects in Taiwan as a result of design
changes.
Delays have been identified as a key factor that increase the construction cost
of the projects worldwide (Kartam, 1999). Design changes are one of the main
causes that lead to such construction delays. Arditi et al. (1985) found that 3.54
percent of the delays in public projects in Turkey were caused by design changes. In
the UK, 49 percent of the delays are caused by factors related to design changes
(Sullivan and Harris, 1986). In Nigeria, this percentage is reported to be as high as
71 percent (Okpala and Aniekwu, 1988).
5
Consulting engineers are familiar with the methods of pricing their
consultancy design services at the tender stage. These methods are well developed
and well documented as it will be seen in the next chapter. When changes are
introduced, there is a lack of an affective method to assess their fee. Normally
consulting engineers either estimate their extra design fee for modifying the original
design in a lump-sum basis or alternatively predict the most likely man-hours that are
needed to carry out the change; or keep record of the man-hours they spend to
execute the changes. The consulting engineers then submit the man-hours to their
clients for payments. Clients, on the other hand, do not always accept the submitted
man-hours because they feel the man-hours are overestimated due to lack of trust. At
the same time, there is no well accepted alternative methods that might be used to
quantify the design changes and hence to assess their fee. Such situations may
increase the possibility of contractual disputes, affect the relationships and lead to
dissatisfaction and disappointment to both the clients and the consulting engineers.
Recognizing these facts, there is an obvious need for in depth study to address these
issues and to find a practical solution that might be used to assess the fee of
modifying the original design changes. This research is a step toward satisfying this
need.
1.3 Aim and Objectives
It is a well known fact that many design changes are most likely inevitable
during the life cycle of the projects. These changes might be minor so that no major
claims on fee or time extension takes place or might be major in which it results in
main claims. While the original consultancy design fee is normally stated in the
contract documents based on the tender submission and negotiation, there is no
practical and acceptable method yet to assess the fee of modifying the original
design. The primary aim of this research work is to formulate practical procedures
for the assessment of the structural design changes so that an enhancement can be
made to the existing practice. The result of this study will put forward practical
means of avoiding and resolving the disputes caused by the lack of appropriate
method of assessing the fee of design changes.
6
The review and investigation of this research work are to be carried out with
the following objectives:
(1) To identify the sources, the causes, and the impacts of the design changes on reinforced concrete buildings;
(2) To establish corrective actions and preventive measures to minimise the
avoidable design changes; (3) To identify and evaluate the various methods for assessing the fee of the
structural design changes and to identify their limitations; (4) To develop an alternative method to assess the fee of the structural
design changes for low rise RCC buildings; (5) To develop guidelines to improve the consultancy design documents; and
(6) To develop guidelines to manage the design changes when they occur
1.4 Scope and Limitations of the Research
In this study, the proposed method for assessing the fee of the structural
design changes is based on designing 12 number small scale low rise reinforced
concrete buildings consisting of one floor to four floors. These buildings have
already been constructed in the Sultanate of Oman prior to this study. The buildings
under this research work have been designed using both manual calculations and
STAAD Pro 2003 software and have been drafted by AutoCAD 2000 software. The
investigation and the scopes of this study were carried out in the Sultanate of Oman
and hence limited to the typical standard details and normal practice in the country.
The finding can only be applied to these types of projects.
7
1.5 Brief Research Methodology
Research methodology provides a general plan and necessary steps to execute
the research in a scientific manner. It is a logical model for collecting the
information, analysing the data and interpreting the findings of the research. It is also
the necessary methods that lead to achieve the aim and the objectives of the research.
To this end, Figure 1.1 outlines a flow chart for the methodology of this research. A
more detailed research methodology is discussed in Chapter 5.
1.6 Justification of the Research
The idea of this work came from the past experience and knowledge on the
extent of the problems and the size of the claims associated with the structural design
changes. In many cases, design changes lead to disputes due to lack of proper
guidelines to manage them and lack of appropriate methods on their fee variation
assessment. The topic went through progressive refinement taken into consideration
the interest in the area of the study, findings of previous works as well as the
professional opinion from the industry in order to explore areas of dissatisfaction.
As a result of this initial investigation, the topic of this research is advanced to the
state that it is delineated sufficiently for the aim and objectives of the research and
importantly to make significant contribution to the subject.
8
Establishing the Aim
Identifying the Problem
Identifying the Objectives
Identifying the Impact of Design
Changes
Identifying up to Date Development
for Managing Design Changes
Identifying the Sources and Causes of Design Changes
Identifying the Existing Methods for Assessing the Fee of Design Changes and their Limitations
Verifying the Sources, Causes and Impacts of
Design Changes
INITIATION OF THE RESEARCH
INTERVIEWS WITH PROFESSIONALS
CASE STUDIES
Giving Actual Examples on the Size and Effect of
Design Changes
Demonstrating the Limitations of the Existing
Methods in the Practice
LITERATURE REVIEW
Cont.
Figure 1.1 : Research Methodology Flow Chart
9
Establishing the Important Level of the Sources, Causes
and Impacts of Design Changes
Identifying the Limitations of the
Existing Methods for Assessing the Fee of
Design Changes
BUILDINGS DESIGN MANUALLY AND BY STAAD PRO SOFTWARE AND DRAFTING BY
AUTOCAD FOR DEVELOPING AN ALTERNATIVE METHOD FOR ASSESSING
THE FEE OF DESIGN CHANGES
VALIDATION OF THE DEVELOPED METHOD BY QUESTIONNAIRE
SURVEY
CONCLUSIONS, RECOMMENDATIONS AND
SUGGESTIONS FOR FUTURE RESEARCH
QUESTIONNAIRE SURVEY
Identifying the Possible Preventive
Measures to Minimise Design
Changes
DEVELOPMENT OF GUIDELINES FOR MANAGING DESIGN CHANGES
VALIDATION OF THE DEVELOPED GUIDELINES BY DELPHI METHOD
PILOT STUDY
Figure 1.1 : Research Methodology Flow Chart (Continue)
10
1.7 Significance of the Study
The study is unique in the sense that no previous attempts have been made on
the subject in spite of wide spread dissatisfaction associated with design changes,
their impact and their fee assessment on reinforced concrete buildings. Surely it will
improve the industry’s understanding on the negative aspects that are related to
design changes and help to reduce the possible disputes in this regard. The study
will improve the efficiency, effectiveness and satisfaction in the construction practice
and it will make a contribution to the construction industry in general and especially
to the consulting engineering firms by developing a practical method of charging for
design changes. The study will help define the related issues and directions that need
to be addressed in the future.
1.8 Research Contributions
The main contribution of this study to the body of knowledge falls on the
following aspects: Firstly, the study gives emphasis on identifying the sources,
causes and impacts of design changes on reinforced concrete buildings as well as on
establishing corrective actions and/or preventive measures to minimise the avoidable
ones. This study has developed practical and reliable method for fee variation
assessment that might be implemented by professionals to assess the fee of changing
or modifying the original design of reinforced concrete buildings. In addition, it is
anticipated that the study will provide set of guidelines to improve the current design
contract documents with respect to design changes and another set of guidelines to
manage their claims
1.9 Organization of the Thesis
This thesis comprises four major components which can be summarized as
follows:
11
• Providing background, identifying the problems of design changes and reviewing
their associated issues through literature searching;
• Investigating and validating the main topics related to this research work through
interviews with the professionals working in the construction industry, case
studies and a questionnaire survey;
• Making a contribution to the body of knowledge by developing an alternative
method to assess the fee of the structural design change when they occur; and
• Providing practical guidelines to manage design changes.
The four main components of the research are presented in nine chapters and
are briefly described as follow:
Chapter 1 introduces the background of the research, its aim and objectives. It also
discusses the brief research methodology used; the research justification; the
significant of the study; the contributions; the scope of the research and a brief
summary on the structure of the thesis.
Chapter 2 presents the findings from the literature review. It focuses on the issues
of design changes which include the following:
• definitions and classifications of the design changes;
• sources, causes and impacts of the design changes; and
• new developments for managing design changes
Chapter 3 focuses on the discussion related to the principle of consulting
engineering practice. The emphasis is given to these issues:
• the definitions of the clients and the consulting engineers
• the reasons for consulting engineering services
• the services provided by the consulting engineers
12
• the method of charging for consulting engineering services
Chapter 4 presents an overview of the construction industry in the Sultanate of
Oman from which the majority of the data for this study has been carried out. It
gives basic information about Oman as a country; brief highlights on Omani
economy; the construction sector in Oman and the consulting engineering services in
the country.
Chapter 5 discusses the methodology adopted for this research. It starts by
discussing the method used to justify the need for this research through the
interviews with the professionals, case studies and questionnaire survey. Then it
discusses the method used for data collection. An explanation was given to each
method in term of their relation to the study, selection criteria and the anticipated
result of each method.
Chapter 6 presents the data collection for the initial investigation to establish the
extent of the problems associated with design changes and to justify the need for this
research as perceived by the professionals in the industry. Interviews with
professionals, three case studies and two stages questionnaire survey have been
conducted and their results were presented in this chapter. In the interviews and in
the case studies, the main problems of design changes have been identified as well as
their causes, sources and impacts on the projects. From the results of the
questionnaire survey, the significant level of the causes, sources and impacts of
design change were identified along with the possible corrective measures to
minimise them. The limitations of the existing methods are presented in this chapter
as well.
Chapter 7 presents the development of the proposed method to assess the fee of the
structural design changes in RCC buildings. It starts by highlighting the general
approach that has been adopted for generating the data. The results have been shown
in tables and illustrated graphically for comparisons. From the obtained data, a
method for assessing the fee of the structural design changes has been developed.
Practical examples to illustrate the use of the proposed method are provided. The
13
chapter also provides the result of the questionnaire survey that has been conducted
for validating the developed method.
Chapter 8 discusses the development of guidelines to manage design changes. It
also provides in details the findings from the Delphi study that has been used as a
method to validate the developed guidelines.
Chapter 9 concludes the results of the research. Discussions are made on the
achievement of the objectives of the study, on the contribution of the research to the
existing knowledge and recommendations are made for future research on the
subject.
265
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