Steel Structures Design ASD/LRFD

573 Pages·2011·4.19 MB·573\573

by  Alan Williams

Steel
Structures
Design
About the Author
Alan Williams, Ph.D., S.E., F.I.C.E., C. Eng., is a registered
structural engineer in California who has had extensive
experience in the practice and teaching of structural engi-
neering. In California, he has worked as a Senior Trans-
portation Engineer in the Department of Transportation
and as Principal for Structural Safety in the Division of the
State Architect. His prior positions include Professor of
Structural Analysis at Ahmadu Bello University, Nigeria,
and consulting structural engineer in South Africa and
the United States. Dr. Williams’ practical experience
includes the design and construction of bridges, schools,
and commercial and industrial structures.
The author obtained his bachelor of science degree
and doctorate from Leeds University and has published
13 papers and nine books on structural engineering top-
ics. Dr. Williams is a member of the Structural Engineers
Association of Southern California, Fellow and Life
Member of the Institution of Civil Engineers, and a
Chartered Engineer in the United Kingdom.
About the International Code Council
The International Code Council (ICC), a membership
association dedicated to building safety, fire prevention,
and energy efficiency, develops the codes and standards
used to construct residential and commercial buildings,
including homes and schools. The mission of ICC is to
provide the highest quality codes, standards, products,
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formance of the built environment. Most U.S. cities, coun-
ties, and states choose the International Codes, building
safety codes developed by the ICC. The International
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nations outside the United States. The ICC is also dedi-
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Steel
Structures
Design
Alan Williams
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Contents
Preface ..................................................... xv
Nomenclature ............................................... xvii
1 Steel Buildings and Design Criteria ........................... 1
1.1 Introduction ........................................... 1
1.2 Types of Steel Buildings ................................. 5
1.3 Building Codes and Design Criteria ....................... 8
1.4 ASD and LRFD Concepts ................................ 9
References .................................................. 1 2
Problems ................................................... 1 2
2 Design Loads ............................................... 15
2.1 Introduction ........................................... 1 5
2.2 Dead Loads ............................................ 1 6
Tributary Area ....................................... 1 6
Slab Supports ........................................ 1 6
Dead Load Applied to Beams .......................... 1 7
Dead Load Applied to Girders ......................... 1 9
Dead Load Applied to Columns ........................ 2 1
Two-Way Slabs ...................................... 2 4
2.3 Live Loads ............................................ 2 5
Continuous Beam Systems ............................ 2 5
Influence Area ....................................... 2 6
Reduction in Floor Live Load .......................... 2 7
Reduction in Roof Live Load .......................... 3 1
Combined Dead and Live Load ........................ 3 3
2.4 Snow Loads ........................................... 3 4
Flat Roof ............................................ 3 4
Ground Snow Load .................................. 3 4
Flat Roof Snow Load ................................. 3 4
Exposure Factor ...................................... 3 5
Thermal Factor ...................................... 3 5
Importance Factor .................................... 3 5
Rain-on-Snow Surcharge Load ......................... 3 6
Snow Drifts on Lower Roofs ........................... 3 8
Leeward Snow Drifts ................................. 3 8
Windward Snow Drifts ............................... 4 2
Sloped Roof Snow Load ............................... 4 4
Slope Factor ......................................... 4 5
Warm Roof Slope Factor .............................. 4 5
Cold Roof Slope Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
v
vi Contents Contents vii
Unbalanced Snow Load for Hip and Gable Roofs ........ 4 6
Unbalanced Snow Load for Gable Roof with
W Ä 20 ft ........................................ 4 7
Unbalanced Snow Load for Gable Roof with
W > 20 ft ....................................... 4 8
Sliding Snow ........................................ 5 1
Snow Load on Continuous Beam Systems ............... 5 4
2.5 Soil Lateral Load ....................................... 5 5
Earth Pressure at Rest ................................. 5 5
2.6 Flood Loads ........................................... 5 5
Loads during Flooding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5
Hydrostatic Loads .................................... 5 5
Hydrodynamic Loads ................................ 5 5
Wave Loads ......................................... 5 6
Impact Loads ........................................ 5 6
2.7 Rain Loads ............................................ 5 6
Design Rain Loads ................................... 5 6
Ponding Instability ................................... 5 7
2.8 Wind Loads ........................................... 5 7
Exposure Category ................................... 5 9
Basic Wind Speed .................................... 5 9
Low-Rise Building ................................... 6 1
Regular Building ..................................... 6 1
Simple Diaphragm Building ........................... 6 1
Velocity Pressure Exposure Coefficient .................. 6 1
Site Topography ..................................... 6 1
Directionality Factor .................................. 6 2
Velocity Pressure ..................................... 6 2
ASCE 7 Chapter 28 Part 1—Envelope Procedure ......... 6 3
Rigidity of the Structure ............................... 6 4
Gust Effect Factor .................................... 6 4
Enclosure Classifications .............................. 6 4
Design Wind Pressure on MWFRS for Low-Rise,
Rigid Buildings .................................... 6 5
Design Wind Pressure on Components and Cladding . . . . . 6 7
Design of Components and Cladding Using ASCE 7
Sec. 30.4 ........................................... 6 8
IBC Alternate All-Heights Method ...................... 7 1
Velocity Pressure Exposure Coefficient .................. 7 2
Topography Factor ................................... 7 2
Wind Stagnation Pressure ............................. 7 2
Wind Importance Factor .............................. 7 3
Net-Pressure Coefficient .............................. 7 3
Design Wind Pressure on MWFRS: IBC Alternate
All-Heights Method ................................ 7 3
Design Wind Pressure on Components and Cladding:
IBC Alternate All-Heights Method .................... 7 6
vi Contents Contents vii
2.9 Seismic Loads .......................................... 7 8
Ground Motion Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 0
Site Classification Characteristics ....................... 8 0
Site Coefficients ...................................... 8 0
Adjusted Earthquake Response Accelerations ............ 8 1
Design Response Acceleration Parameters ............... 8 1
Occupancy Category and Importance Factors ............ 8 3
Seismic Design Category .............................. 8 3
Seismic Force-Resisting System ........................ 8 5
Response Modification Coefficient ...................... 8 6
Fundamental Period of Vibration ....................... 8 9
Seismic Response Coefficient .......................... 8 9
Effective Seismic Weight .............................. 9 2
Seismic Base Shear ................................... 9 3
Vertical Distribution of Seismic Forces .................. 9 3
Diaphragm Loads .................................... 9 5
Flexible Diaphragms ................................. 9 6
Anchorage of Structural Walls to Diaphragms ............ 9 9
Rigid Diaphragms .................................... 104
Lateral Design Force on Structural Walls ................ 109
Lateral Design Force on Parapets ....................... 109
Redundancy Factor ................................... 110
2.10 Load Combinations ..................................... 114
Strength Design Load Combinations .................... 115
Allowable Stress Load Combinations ................... 117
Strength Design Special Load Combinations ............. 119
Allowable Stress Design Special Load Combinations ...... 120
2.11 Serviceability Criteria ................................... 120
Deflection ........................................... 121
Drift ................................................ 121
Vibration ............................................ 122
Durability ........................................... 122
References .................................................. 122
Problems ................................................... 123
3 Behavior of Steel Structures under Design Loads ............... 129
3.1 Introduction ........................................... 129
3.2 Gravity Load-Resisting Systems .......................... 129
Simple Connections .................................. 129
Fully Restrained (FR) Moment Connections ............. 135
Partially Restrained (PR) Moment Connections .......... 140
3.3 Lateral Load-Resisting Systems .......................... 144
Diaphragms ......................................... 144
Collectors ........................................... 145
Steel Deck Diaphragms ............................... 151
Frames Subjected to Lateral Forces ..................... 156
viii Contents Contents ix
3.4 Approximate Methods for Laterally Loaded Frames ......... 160
Portal Method ....................................... 160
Cantilever Method ................................... 163
References .................................................. 167
Problems ................................................... 168
4 Design of Steel Beams in Flexure .............................. 171
4.1 Introduction ........................................... 171
Flexural Limit States .................................. 171
Lateral Bracing of Beams .............................. 172
Design Flexural Strength and Allowable Flexural Strength ... 173
4.2 Plastic Moment of Resistance ............................ 175
Shape Factor and ASD ................................ 176
Built-Up Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
4.3 Compact, Noncompact, and Slender Sections .............. 179
Compact Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Noncompact Section ................................. 181
Slender Section ...................................... 182
4.4 Lateral-Torsional Buckling Modification Factor ............. 182
4.5 Lateral-Torsional Buckling ............................... 185
Plastic Mode: L < L ................................. 185
b p
Plastic Mode Extended: L < L ≤ L ..................... 187
p b m
Inelastic Mode: L < L ≤ L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
p b r
Elastic Mode: L > L ................................... 190
b r
4.6 Weak Axis Bending ..................................... 191
Compact Flanges ..................................... 191
Noncompact Flanges ................................. 192
4.7 Biaxial Bending ........................................ 194
Overhead Traveling Bridge Crane ...................... 195
4.8 Singly Symmetric Sections in Bending ..................... 198
Plastic Mode ........................................ 199
Lateral-Torsional Buckling ............................ 199
Flange Local Buckling ................................ 199
Stem Local Buckling .................................. 200
4.9 Redistribution of Bending Moments in Continuous Beams ... 201
4.10 Deflection Limits ....................................... 204
References .................................................. 204
Problems ................................................... 204
5 Design of Steel Beams for Shear and Torsion ................... 209
5.1 Introduction ........................................... 209
5.2 Shear in Beam Webs .................................... 211
Web Yielding ........................................ 212
Inelastic Buckling .................................... 214
Elastic Buckling ...................................... 216
5.3 Weak Axis Shear ....................................... 218
5.4 Longitudinal Shear in Built-Up Sections ................... 219
viii Contents Contents ix
5.5 Block Shear ........................................... 221
Block Shear Strength for Bolted Connections ............. 222
Effective Bolt Hole Diameter and Net Area .............. 223
Block Shear Strength for Welded Connections ............ 225
Block Shear Strength for Coped Beams .................. 226
5.6 Web Local Yielding ..................................... 228
Bearing on Concrete .................................. 229
Web Yielding at Support .............................. 231
Web Yielding at Girder Interior ........................ 233
5.7 Web Crippling ......................................... 234
5.8 Web Sidesway Buckling ................................. 235
5.9 Design for Torsion ...................................... 237
Torsion in Closed Sections ............................. 237
Torsion in Open Sections .............................. 238
Specification Provisions ............................... 239
Round HSS Subject to Torsion ......................... 240
Rectangular HSS Subject to Torsion ..................... 241
W-Shape Subject to Torsion ............................ 244
References .................................................. 249
Problems ................................................... 250
6 Design of Compression Members ............................. 255
6.1 Introduction ........................................... 255
Compression Limit State .............................. 255
6.2 Effective Length ........................................ 257
Tabulated Factors .................................... 257
6.3 Alignment Charts ...................................... 259
Alignment Chart for Braced Frame ..................... 260
Alignment Chart for Sway Frame ...................... 261
Stiffness Reduction Factors ............................ 263
6.4 Axially Loaded Compression Members .................... 264
Flexural Buckling of Members without Slender
Elements .......................................... 264
Torsional and Flexural-Torsional Buckling of Members
without Slender Elements ........................... 268
Single Angle Compression Members without Slender
Elements .......................................... 271
Members with Slender Elements ....................... 273
6.5 Built-Up Sections ....................................... 279
6.6 Column Base Plates ..................................... 282
Concrete Footing Capacity ............................ 282
Base Plate Thickness .................................. 285
6.7 Column Flanges with Concentrated Forces ................. 287
Introduction ......................................... 287
Flange Local Bending ................................. 287
Web Compression Buckling ........................... 290
Web Panel Zone Shear ................................ 292