bangladesh national building code

946 Pages·2015·52.44 MB·English

by  Raquib Ahsan

BANGLADESH NATIONAL
BUILDING CODE
Volume 2 of 3
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FINAL DRAFT
2015
Housing and Building Research Institute
Volume 1

PART 1 SCOPE AND DEFINITION
PART 2 ADMINISTRATION AND ENFORCEMENT
PART 3 GENERAL BUILDING REQUIREMENTS, CONTROL AND
REGULATION
PART 4 FIRE PROTECTION
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PART 5 BUILDING MATERIALS
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PART 6 STRUCTURAL 5DESIGN
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PART 7 CONSTRUCTION PRACTICES AND SAFETY
PART 8 BUILDING SERVICES

PART 9 ADDITION, ALTERATION TO AND CHANGE OF USE OF
EXISTING BUILDINGS
PART 10 SIGNS AND OUT-DOOR DISPLAY
PART 6

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PART 6

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CHAPTER 1 DEFINITIONS AND GENERAL REQUIREMENTS 6-1

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CHAPTER 2 LOADS ON BUILDINGS AND STRUCTURES 6-25
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CHAPTER 3 SOILS AND FOUNDATIONS N 6-143
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CHAPTER 4 BAMBOO F 6-223

CHAPTER 5 CONCRETE MATERIA5L 6-241
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CHAPTER 6 STRENGTH DE0SIGN OF REINFORCED CONCRETE
STRUCTURE2S 6-261

CHAPTER 7 MASONCRY STRUCTURES 6-349
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CHAPTER 8 DETAILING OF REINFORCED CONCRETE STRUCTURES 6-395
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CHAPTER 9 PRESTRESSED CONCRETE STRUCTURES 6-439
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CHAPTER 10 STEEL STRUCTURES 6-477
CHAPTER 11 TIMBER 6-661
CHAPTER 12 FERROCEMENT STRUCTURES 6-703
CHAPTER 13 STEEL-CONCRETE COMPOSITE STRUCTURAL MEMBERS 6-723
Appendices 6-743
TABLE OF CONTENTS

PART 6 STRUCTURAL DESIGN
Chapter 1 DEFINITIONS AND GENERAL REQUIREMENTS
1.1 INTRODUCTION 6-1
1.1.1 Scope 6-1
1.1.2 Definitions 6-1
1.1.3 Symbols and Notation 6-2
1.2 BASIC CONSIDERATIONS 6-3
1.2.1 General 6-3
1.2.2 Buildings and Structures 6-3
1.2.3 Building and Structure Occupancy Categories 6-3
1.2.4 Safety 6-4
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1.2.5 Serviceability 6-5
1.2.6 Rationality F 6-5
1.2.7 Analysis A 6-5
1.2.8 Distribution of Horizontal Shear R 6-6
1.2.9 Horizontal Torsional Moments D 6-6
1.2.10 Stability Against Overturning and Sliding 6-6

1.2.11 Anchorage L 6-6
1.2.12 General Structural Integrity A 6-6
1.2.13 Proportioning of Structural Elements N 6-6
1.2.14 Walls and Framing I 6-7
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1.2.15 Additions to Existing Structures 6-7

1.2.16 Phased Construction 5 6-7
1.2.17 Load Combinations and Stres1s Increase 6-7
1.3 STRUCTURAL SYSTEMS 0 6-7
1.3.1 General 2 6-7
1.3.2 Basic Structural Syst ems 6-7
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1.3.3 Combination of Structural Systems 6-9
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1.3.4 Structural Configurations 6-9
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1.4 DESIGN FOR GRAVITY LOADS 6-10
1.4.1 GeneralB 6-10
1.4.2 Floor Design 6-10
1.4.3 Roof Design 6-11
1.4.4 Reduction of Live Loads 6-11
1.4.5 Posting of Live Loads 6-11
1.4.6 Restrictions on Loading 6-12
1.4.7 Special Considerations 6-12
1.4.8 Deflection and Camber 6-12
1.5 DESIGN FOR LATERAL LOADS 6-12
1.5.1 General 6-12
1.5.2 Selection of Lateral Force For Design 6-12
1.5.3 Design for Wind Load 6-13
1.5.4 Design for Earthquake Forces 6-14
1.5.5 Overturning Requirements 6-15
1.5.6 Drift and Building Separation 6-15
1.5.7 Building Separation 6-16
1.5.8 P-Delta Effects 6-16
1.5.9 Uplift Effects 6-16

6-i Vol. 2
Part 6
Structural Design
1.6 DESIGN FOR MISCELLANEOUS LOADS 6-16
1.6.1 General 6-16
1.6.2 Self-Straining Forces 6-16
1.6.3 Stress Reversal and Fatigue 6-16
1.6.4 Flood, Tidal/Storm Surge and Tsunami 6-17
1.6.5 Rain Loads 6-17
1.6.6 Other Loads 6-17
1.7 DETAILED DESIGN REQUIREMENTS 6-17
1.7.1 General 6-17
1.7.2 Structural Framing Systems 6-18
1.7.3 Detailing Requirements for Combinations of Structural Systems : 6-18
1.8 FOUNDATION DESIGN REQUIREMENTS 6-20
1.8.1 General 6-20
1.8.2 Soil Capacities 6-20
1.8.3 Superstructure-to-Foundation Connection 6-20
1.8.4 Foundation-Soil Interface 6-21
1.8.5 Special Requirements for Footings, Piles and Caissons In Seismic Zones 2, 3 And 4 6-21
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1.8.6 Retaining Wall Design 6-21
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1.9 DESIGN AND CONSTRUCTION REVIEW 6-21
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1.9.1 Design Document 6-21
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1.9.2 Design Report 6-21
1.9.3 Structural Drawings and Material Specifications D 6-22
1.9.4 Design Review 6-23
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1.9.5 Construction Observation 6-23
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Chapter 2 LOADS ON BUILDINGS AND STRUCTURES
2.1 Introduction I 6-25
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2.1.1 Scope 6-25

2.1.2 Limitations 5 6-25
2.1.3 Terminology 1 6-25
2.1.4 Symbols and Notation 0 6-30
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2.2 Dead Loads 6-35

2.2.1 General C 6-35
2.2.2 Definition 6-35
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2.2.3 Assessment of Dead Load 6-35
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2.2.4 Weight of Materials and Constructions 6-35
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2.2.5 Weight of Permanent Partitions 6-36
2.2.6 Weight of Fixed Service Equipment 6-37
2.2.7 Additional Loads 6-37
2.3 LIVE LOADS 6-37
2.3.1 General 6-37
2.3.2 Definition 6-37
2.3.3 Minimum Floor Live Loads 6-37
2.3.4 Uniformly Distributed Loads 6-37
2.3.5 Concentrated Loads 6-37
2.3.6 Provision for Partition Walls 6-41
2.3.7 More Than One Occupancy 6-41
2.3.8 Minimum Roof Live Loads 6-41
2.3.9 Loads not Specified 6-41
2.3.10 Partial Loading and Other Loading Arrangements 6-41
2.3.11 Other Live Loads 6-42
2.3.12 Impact and Dynamic Loads 6-42
2.3.13 Reduction of Live Loads 6-42
2.3.14 Reduction in Roof Live Loads 6-44

6-ii Vol. 2
Part 6
Structural Design
2.4 WIND LOADS 6-44
2.4.1 General 6-44
2.4.2 Method 1—Simplified Procedure 6-45
2.4.3 Method 2—Analytical Procedure 6-47
2.4.4 Basic Wind Speed 6-47
2.4.5 Importance Factor 6-49
2.4.6 Exposure 6-49
2.4.7 Topographic Effects 6-50
2.4.8 Gust Effect Factor 6-50
2.4.9 Enclosure Classifications 6-52
2.4.10 Pressure And Force Coefficients 6-52
2.4.11 Design Wind Loads on Enclosed and Partially Enclosed Buildings 6-53
2.4.12 Design Wind Loads on Open Buildings with Monoslope, Pitched, or Troughed Roofs 6-56
2.4.13 Design Wind Loads on Solid Free Standing Walls and Solid Signs 6-56
2.4.14 Design Wind Loads on Other Structures 6-57
2.4.15 Rooftop Structures and Equipment for Buildings with h ≤ 18.3 m 6-57
2.4.16 Method 3—Wind Tunnel Procedure 6-57
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2.4.17 Dynamic Response 6-57
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2.5 EARTHQUAKE LOADS 6-90
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2.5.1 General 6-90
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2.5.2 Earthquake Resistant Design – Basic Concepts 6-90
2.5.3 Investigation And Assessment Of Site Conditions D 6-92
2.5.4 Earthquake Ground Motion 6-94
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2.5.5 Building Categories 6-99
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2.5.6 Static Analysis Procedure 6-104
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2.5.7 Equivalent Static Analysis 6-105
2.5.8 Dynamic Analysis Methods I 6-109
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2.5.9 Response Spectrum Analysis (RSA) 6-110

2.5.10 Linear Time History Analysis (LT5HA) 6-111
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2.5.11 Non-Linear Time History Analysis (NTHA) 6-112
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2.5.12 Non-Linear Static Analysis (NSA) 6-114
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2.5.13 Earthquake Load Combinations 6-116

2.5.14 Drift and DeformatCion 6-117
2.5.15 Seismic Design For Nonstructural Components 6-118
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2.5.16 Design For Seismically Isolated Buildings 6-120
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2.5.17 Buildings with Soft Storey 6-128
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2.5.18 Non-Building Structures 6-129
2.6 MISCELLANEOUS LOADS 6-129
2.6.1 General 6-129
2.6.2 Rain Loads 6-129
2.6.3 Loads Due to Flood and Surge 6-129
2.6.4 Temperature Effects 6-137
2.6.5 Soil and Hydrostatic Pressure 6-137
2.6.6 Loads due to Explosions 6-138
2.6.7 Vertical Forces on Air Raid Shelters 6-139
2.6.8 Loads on Helicopter Landing Areas 6-139
2.6.9 Erection and Construction Loads 6-140
2.7 COMBINATIONS OF LOADS 6-140
2.7.1 General 6-140
2.7.2 Combinations of Load effects for Allowable Stress Design Method 6-140
2.7.3 Combinations of Load effects for Strength Design Method 6-141
2.7.4 LOAD COMBINATIONS FOR EXTRAORDINARY EVENTS 6-141
2.7.5 Load Combination for Serviceability 6-141
2.8 LIST OF RELATED APPENDICES 6-142

6-iii Vol. 2
Part 6
Structural Design
Chapter 3 SOILS AND FOUNDATIONS
3.1 GENERAL 6-143
3.2 SCOPE 6-143
3.3 DEFINITIONS AND SYMBOLS 6-144
3.3.1 Definitions 6-144
3.3.2 Symbols and Notation 6-148
3.4 SITE INVESTIGATIONS 6-151
3.4.1 Sub-Surface Survey 6-151
3.4.2 Sub-Soil Investigations 6-151
3.4.3 Methods of Exploration 6-151
3.4.4 Number and Location of Investigation Points 6-152
3.4.5 Depth of Exploration 6-153
3.4.6 Sounding and Penetration Tests 6-154
3.4.7 Geotechnical Investigation Report 6-154
3.5 IDENTIFICATION, CLASSIFICATION AND DESCRIPTION OF SOILS 6-155
3.5.1 Identification of Soils 6-155
3.5.2 Particle Size Classification of Soils 6-155
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3.5.3 Engineering Classification of Soils 6-155
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3.5.4 Identification and Classification of Organic Soils 6-158
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3.5.5 Identification and Classification of Expansive Soils 6-158
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3.5.6 Identification and Classification of Collapsible Soils 6-158
3.5.7 Identification and Classification of Dispersive Soils D 6-159
3.5.8 Identification and Classification of Soft Inorganic Soils 6-160
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3.6 MATERIALS 6-160
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3.6.1 Concrete 6-160
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3.6.2 Steel 6-160
3.6.3 Timber I 6-163
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3.7 TYPES OF FOUNDATION 6-163

3.7.1 Shallow Foundations 5 6-163
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3.7.2 Deep Foundations 6-163
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3.7.3 Raft/Mat 6-164
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3.7.4 Deep Foundations 6-164

3.7.5 Driven Piles C 6-164
3.7.6 Bored Piles/Cast-in-Situ Piles 6-164
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3.7.7 Drilled Pier/Drilled Shafts 6-164
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3.7.8 Caisson/Well 6-164
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3.8 SHALLOW FOUNDATION 6-165
3.8.1 Distribution of Bearing Pressure 6-165
3.8.2 Dimension of Footings 6-165
3.8.3 Thickness of Footing 6-165
3.8.4 Footings in Fill Soil 6-165
3.8.5 Soil and Rock Property Selection 6-165
3.8.6 Minimum Depth of Foundation 6-166
3.8.7 Scour 6-166
3.8.8 Mass Movement of Ground in Unstable Areas 6-166
3.8.9 Foundation Excavation 6-166
3.8.10 Design Considerations for Raft foundation 6-167
3.9 GEOTECHNICAL DESIGN OF SHALLOW FOUNDATIONS 6-167
3.9.1 General 6-167
3.9.2 Design Load 6-167
3.9.3 Bearing Capacity of Shallow Foundations 6-168
3.9.4 Settlement of Shallow Foundation 6-169
3.9.5 Dynamic Ground Stability or Liquefaction Potential for Foundation Soils 6-171
3.9.6 Structural Design of Shallow Foundations 6-172

6-iv Vol. 2
Part 6
Structural Design
3.10 GEOTECHNICAL DESIGN OF DEEP FOUNDATIONS 6-175
3.10.1 Driven Precast Piles 6-175
3.10.2 Driven Cast-in-Place Concrete Piles 6-186
3.10.3 Prestressed Concrete Piles 6-187
3.10.4 Bored Piles 6-188
3.10.5 Settlement of Driven and Bored Piles 6-191
3.10.6 Drilled Shafts/ Drilled Piers 6-194
3.11 FIELD TESTS FOR DRIVEN PILES AND DRILLED SHAFTS 6-205
3.11.1 Integrity Test 6-205
3.11.2 Axial Load Tests for Compression 6-206
3.11.3 Load Test for Uplift Capacity of Driven Pile, Bored Pile and Drilled Shaft 6-209
3.11.4 Load Tests for Lateral Load Capacity 6-210
3.12 EXCAVATION 6-210
3.12.1 Notice to Adjoining Property 6-210
3.12.2 Excavation Work 6-211
3.13 DEWATERING 6-212
3.14 SLOPE STABILITY OF ADJOINING BUILDINGS 6-212
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3.15 FILLS 6-213
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3.15.1 Quality of Fill 6-213
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3.15.2 Placement of Fill 6-213
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3.15.3 Specifications 6-213
3.16 PROTECTIVE RETAINING STRUCTURES FOR FOUNDATIONS/ SDHORE PILES 6-213
3.17 WATERPROOFING AND DAMP-PROOFING 6-213
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3.17.1 General 6-213
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3.17.2 Other Damp-proofing and Waterproofing Requirements 6-215
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3.18 FOUNDATION ON SLOPES 6-216
3.19 FOUNDATIONS ON FILLS AND PROBLEMATIC ISOILS 6-216
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3.19.1 Footings on Filled up Ground 6-216

3.19.2 Ground Improvement 5 6-216
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3.19.3 Soil Reinforcement 6-216
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3.20 FOUNDATION DESIGN FOR DYNAMIC FORCES 6-216
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3.20.1 Effect of Dynamic Forces 6-216

3.20.2 Machine FoundatioCn 6-216
3.21 GEO-HAZARD ANALYSIS FOR BUILDINGS 6-221
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3.22 LIST FO RELATED APPENDICES 6-221
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Chapter 4 BAMBOBO
4.1 SCOPE 6-223
4.2 TERMINOLOGY 6-223
4.2.1 Anatomical Purpose Definitions 6-223
4.2.2 Structural Purpose Definitions 6-225
4.2.3 Definitions Relating to Defects 6-226
4.2.4 Definitions Relating to Drying Degrades 6-226
4.3 SYMBOLS 6-226
4.4 MATERIALS 6-226
4.4.1 Species of Bamboo 6-226
4.4.2 Grouping 6-227
4.4.3 Moisture Content in Bamboo 6-227
4.4.4 Grading of Structural Bamboo 6-229
4.4.5 Taper 6-230
4.4.6 Durability and Treatability 6-230
4.5 PERMISSIBLE STRESSES 6-231
4.6 DESIGN CONSIDERATIONS 6-232
4.7 DESIGN AND TECHNIQUES OF JOINTS 6-234

6-v Vol. 2
Part 6
Structural Design
4.8 STORAGE OF BAMBOO 6-240
4.9 RELATED REFERENCES 6-240
Chapter 5 CONCRETE MATERIAL
5.1 GENERAL 6-241
5.1.1 Scope 6-241
5.1.2 Notation 6-241
5.2 CONSTITUENTS OF CONCRETE 6-241
5.2.1 Cement 6-241
5.2.2 Aggregates 6-241
5.2.3 Water 6-242
5.2.4 Admixtures 6-242
5.3 STEEL REINFORCEMENT 6-243
5.3.1 General 6-243
5.3.2 Deformed Reinforcement 6-243
5.3.3 Plain Reinforcement 6-243
5.3.4 Structural Steel, Steel Pipe or Tubing 6-243
5.4 WORKABILITY OF CONCRETE T 6-244
5.5 DURABILITY OF CONCRETE F 6-244
5.5.1 Special Exposures A 6-244
5.5.2 Sulphate Exposures R 6-244
5.5.3 Corrosion of Reinforcement D 6-245
5.5.4 Minimum Concrete Strength 6-245

5.6 CONCRETE MIX PROPORTION L 6-246
5.6.1 General A 6-246
5.6.2 Proportioning Concrete Mix on the Basis of Field NExperience and/or Trial Mixtures 6-246
5.6.3 Proportioning by Water Cement Ratio I 6-248
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5.6.4 Average Strength Reduction 6-248

5.7 Preparation of Equipment and Place of Deposit 5 6-248
5.8 MIXING 1 6-249
5.9 CONVEYING 0 6-249
5.10 DEPOSITING 2 6-249
5.11 CURING 6-250
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5.12 EVALUATION AND ACCEPTANCE OF CONCRETE 6-250
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5.12.1 General 6-250
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5.12.2 Frequency of Testing 6-250
5.12.3 Laboratory CureBd Specimens 6-251
5.12.4 Field Cured Specimens 6-251
5.12.5 Investigation of Low Strength Test Results 6-251
5.13 PROPERTIES OF CONCRETE 6-252
5.13.1 Strength 6-252
5.13.2 Modulus of Elasticity 6-252
5.13.3 Creep 6-252
5.13.4 Shrinkage 6-252
5.13.5 Thermal Strains 6-253
5.14 CONCRETING IN ADVERSE WEATHER 6-253
5.15 SURFACE FINISH 6-255
5.15.1 Type of Finish 6-255
5.15.2 Quality of Finish 6-255
5.15.3 Type of Surface Finish 6-256
5.15.4 Production 6-256
5.15.5 Inspection and Making Good 6-256
5.15.6 Protection 6-257

6-vi Vol. 2