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Textbook
Unified Design of Steel Structures, 2nd EditionDecember 2011, ©2012
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The text is designed primarily for use in a single course in basic steel design, but may also be used in a second, building oriented course in steel design, depending on the coverage in the first course.
This text is based on the 2010 AISC Specification for Structural Steel Buildings. It addresses in a consistent way both LRFD and ASD design philosophies. It is designed to be used with the 14th edition of the Steel Construction Manual and is directly linked to it with discussions of numerous Manual Tables after the Specification equations have been addressed. This approach gives the student the advantage of knowing what primary resources are available in the Manual and how to use them. Each Chapter starts with a table indicating which sections of the Specification and which Parts of the Manual are to be discussed to assist the student with an understanding of the breadth of topics covered in that chapter.
All examples that rely on LRFD and ASD provisions are fully presented, even if it means some duplication, so that regardless of approach being taught, there will be no need to refer to the other approach example. All homework problems that could be LRFD or ASD are presented both ways so that the instructor may choose the approach they want the student to follow.
1.1 Scope 1
1.2 The Specification 1
1.3 The Manual 3
1.4 AISC Website Resources 4
1.5 Principles of Structural Design 5
1.6 Parts of the Steel Structure 6
1.7 Types of Steel Structures 11
1.7.1 Bearing Wall Construction 11
1.7.2 Beam-and-Column Construction 11
1.7.3 Long-Span Construction 13
1.7.4 High-Rise Construction 14
1.7.5 Single-Story Construction 15
1.8 Design Philosophies 15
1.9 Fundamentals of Allowable Strength Design (ASD) 18
1.10 Fundamentals of Load and Resistance Factor Design (LRFD) 18
1.11 Inelastic Design 19
1.12 Structural Safety 20
1.13 Limit States 22
1.14 Building Codes and Design Specifications 23
1.15 Integrated Design Project 23
1.16 Problems 26
2. Loads, Load Factors, and Load Combinations 27
2.1 Introduction 27
2.2 Building Load Sources 28
2.2.1 Dead Load 28
2.2.2 Live Load 28
2.2.3 Snow Load 29
2.2.4 Wind Load 29
2.2.5 Seismic Load 30
2.2.6 Special Loads 30
2.3 Building Load Determination 31
2.3.1 Dead Load 31
2.3.2 Live Load 32
2.3.3 Snow Load 34
2.3.4 Wind Load 34
2.3.5 Seismic Load 37
2.4 Load Combinations for ASD and LRFD 38
2.5 Load Calculations 39
2.6 Calibration 45
2.7 Problems 46
Multi-Chapter Problems 46
Integrated Design Project 47
3. Steel Building Materials 48
3.1 Introduction 48
3.2 Applicability of the AISC Specification 50
3.3 Steel for Construction 53
3.4 Structural Steel Shapes 55
3.4.1 ASTM A6 Standard Shapes 55
3.4.2 Hollow Shapes 58
3.4.3 Plates and Bars 58
3.4.4 Built-up Shapes 60
3.5 Chemical Components of Structural Steel 60
3.6 Grades of Structural Steel 62
3.6.1 Steel for Shapes 62
3.6.2 Steel for Plates and Bars 65
3.6.3 Steel for Fasteners 67
3.6.4 Steel for Welding 69
3.6.5 Steel for Shear Studs 69
3.7 Availability of Structural Steel 69
3.8 Problems 69
4. Tension Members 71
4.1 Introduction 71
4.2 Tension Members in Structures 71
4.3 Cross-Sectional Shapes for Tension Members 73
4.4 Behavior and Strength of Tension Members 75
4.4.1 Yielding 76
4.4.2 Rupture 76
4.5 Computation of Areas 77
4.5.1 Gross Area 78
4.5.2 Net Area 78
4.5.3 Influence of Hole Placement 82
4.5.4 Effective Net Area 85
4.6 Design of Tension Members 90
4.7 Block Shear 93
4.8 Pin-Connected Members 102
4.9 Eyebars and Rods 105
4.10 Built-Up Tension Members 106
4.11 Truss Members 106
4.12 Bracing Members 106
4.13 Problems 109
Multi-Chapter Problem 111
Integrated Design Project 111
5. Compression Members 112
5.1 Compression Members in Structures 112
5.2 Cross-Sectional Shapes for Compression Members 112
5.3 Compression Member Strength 114
5.3.1 Euler Column 114
5.3.2 Other Boundary Conditions 117
5.3.3 Combination of Bracing and End Conditions 118
5.3.4 Real Column 121
5.3.5 AISC Provisions 124
5.4 Additional Limit States for Compression 131
5.5 Length Effects 131
5.5.1 Effective Length for Inelastic Columns 137
5.6 Slender Elements in Compression 139
5.7 Column Design Tables 145
5.8 Torsional Buckling and Flexural-Torsional Buckling 150
5.9 Single-Angle Compression Members 155
5.10 Built-Up Members 156
5.11 Column Base Plates 157
5.12 Problems 159
Multi-Chapter Problems 162
Integrated Design Project 163
6. Bending Members 1646.1 Bending Members in Structures 164
6.2 Strength of Beams 165
6.3 Design of Compact Laterally Supported Wide-Flange Beams 169
6.4 Design of Compact Laterally Unsupported Wide-Flange Beams 176
6.4.1 Lateral Torsional Buckling 176
6.4.2 Moment Gradient 180
6.5 Design of Noncompact Beams 188
6.5.1 Local Buckling 188
6.5.2 Flange Local Buckling 189
6.5.3 Web Local Buckling 191
6.6 Design of Beams for Weak Axis Bending 193
6.7 Design of Beams for Shear 195
6.8 Continuous Beams 197
6.9 Plastic Analysis and Design of Continuous Beams 199
6.10 Provisions for Double-Angle and Tee Members 202
6.10.1 Yielding 202
6.10.2 Lateral-Torsional Buckling 202
6.10.3 Flange Local Buckling 203
6.10.4 Stem Local Buckling 203
6.11 Single-Angle Bending Members 205
6.11.1 Yielding 206
6.11.2 Leg Local Buckling 206
6.11.3 Lateral-Torsional Buckling 206
6.12 Members in Biaxial Bending 207
6.13 Serviceability Criteria for Beams 208
6.13.1 Deflection 208
6.13.2 Vibration 208
6.13.3 Drift 209
6.14 Concentrated Forces on Beams 210
6.14.1 Web Local Yielding 211
6.14.2 Web Crippling 212
6.15 Open Web Steel Joists and Joist Girders 215
6.16 Problems 218
Multi-Chapter Problems 221
Integrated Design Project 221
7. Plate Girders 2227.1 Background 222
7.2 Homogeneous Plate Girders in Bending 224
7.2.1 Noncompact Web Plate Girders 225
7.2.2 Slender Web Plate Girders 229
7.3 Homogeneous Plate Girders in Shear 237
7.3.1 Nontension Field Action 237
7.3.2 Tension Field Action 239
7.4 Stiffeners for Plate Girders 242
7.4.1 Intermediate Stiffeners 242
7.4.2 Bearing Stiffeners 244
7.4.3 Bearing Stiffener Design 247
7.5 Problems 250
8. Beam-Columns and Frame Behavior 252
8.1 Introduction 252
8.2 Second-Order Effects 253
8.3 Interaction Principles 255
8.4 Interaction Equations 256
8.5 Braced Frames 259
8.6 Moment Frames 266
8.7 Specification Provisions for Stability Analysis and Design 276
8.7.1 Direct Analysis Method 276
8.7.2 Effective Length Method 277
8.7.3 First-Order Analysis Method 277
8.7.4 Notional Loads 277
8.8 Initial Beam-Column Selection 279
8.9 Beam-Column Design Using Manual Part 6 282
8.10 Combined Simple and Moment Frames 285
8.11 Partially Restrained Frames 294
8.12 Bracing Design 302
8.12.1 Column Bracing 303
8.12.2 Beam Bracing 303
8.12.3 Frame Bracing 304
8.13 Tension Plus Bending 306
8.14 Problems 306
Multi-Chapter Problem 311
Integrated Design Project 311
9. Composite Construction 3129.1 Introduction 312
9.2 Advantages and Disadvantages of Composite Beam Construction 315
9.3 Shored versus Unshored Construction 315
9.4 Effective Flange 316
9.5 Strength of Composite Beams and Slab 316
9.5.1 Fully Composite Beams 318
9.5.2 Partially Composite Beams 322
9.5.3 Composite Beam Design Tables 325
9.5.4 Negative Moment Strength 330
9.6 Shear Stud Strength 330
9.6.1 Number and Placement of Shear Studs 331
9.7 Composite Beams with Formed Metal Deck 332
9.7.1 Deck Ribs Perpendicular to Steel Beam 333
9.7.2 Deck Ribs Parallel to Steel Beam 335
9.8 Fully Encased Steel Beams 340
9.9 Selecting a Section 340
9.10 Serviceability Considerations 344
9.10.1 Deflection During Construction 344
9.10.2 Vibration Under Service Loads 345
9.10.3 Live Load Deflections 345
9.11 Composite Columns 348
9.12 Composite Beam-Columns 352
9.13 Problems 356
Multi-Chapter Problem 358
Integrated Design Project 358
10. Connection Elements 359
10.1 Introduction 359
10.2 Basic Connections 359
10.3 Beam-to-Column Connections 361
10.4 Fully Restrained Connections 362
10.5 Simple and Partially Restrained Connections 363
10.6 Mechanical Fasteners 364
10.6.1 Common Bolts 364
10.6.2 High-Strength Bolts 364
10.6.3 Bolt Holes 366
10.7 Bolt Limit States 367
10.7.1 Bolt Shear 368
10.7.2 Bolt Bearing 369
10.7.3 Bolt Tension 370
10.7.4 Slip 376
10.7.5 Combined Tension and Shear in Bearing-Type Connections 377
10.8 Welds 378
10.8.1 Welding Processes 378
10.8.2 Types of Welds 379
10.8.3 Weld Sizes 380
10.9 Weld Limit States 381
10.9.1 Fillet Weld Strength 381
10.9.2 Groove Weld Strength 387
10.10 Connecting Elements 387
10.10.1 Connecting Elements in Tension 387
10.10.2 Connecting Elements in Compression 388
10.10.3 Connecting Elements in Flexure 388
10.10.4 Connecting Elements in Shear 388
10.10.5 Block Shear Strength 388
10.11 Problems 392
11. Simple Connections 396
11.1 Types of Simple Connections 396
11.2 Simple Shear Connections 397
11.3 Double-Angle Connections: Bolted-Bolted 398
11.4 Double-Angle Connections: Welded-Bolted 408
11.5 Double-Angle Connections: Bolted-Welded 412
11.6 Double Angle Connections: Welded-Welded 414
11.7 Single-Angle Connections 414
11.8 Single-Plate Shear Connections 422
11.9 Seated Connections 427
11.10 Light Bracing Connections 432
11.11 Beam Bearing Plates and Column Base Plates 443
11.12 Problems 449
Multi-Chapter Problem 452
Integrated Design Project 452
12. Moment Connections 453
12.1 Types of Moment Connections 453
12.2 Limit States 456
12.3 Moment Connection Design 456
12.3.1 Direct-Welded Flange Connection 456
12.3.2 Welded Flange Plate Connection 461
12.3.3 Bolted Flange Plate Connection 467
12.4 Column Stiffening 474
12.4.1 Flange Local Bending 475
12.4.2 Web Local Yielding 475
12.4.3 Web Crippling 476
12.4.4 Web Compression Buckling 476
12.4.5 Web Panel Zone Shear 477
12.5 Problems 482
Multi-Chapter Problem 483
Integrated Design Project 483
13. Steel Systems for Seismic Resistance 484
13.1 Introduction 484
13.2 Expected Behavior 485
13.3 Moment-Frame Systems 486
13.3.1 Special Moment Frames (SMF) 487
13.3.2 Intermediate Moment Frames (IMF) and Ordinary Moment Frames (OMF) 490
13.4 Braced-Frame Systems 490
13.4.1 Special Concentrically Braced Frames (SCBF) 491
13.4.2 Ordinary Concentrically Braced Frames (OCBF) 494
13.4.3 Eccentrically Braced Frames (EBF) 494
13.5 Other Framing Systems 496
13.5.1 Special Truss Moment Frames (STMF) 496
13.5.2 Buckling-Restrained Braced Frames (BRBF) 497
13.5.3 Special Plate Shear Walls (SPSW) 498
13.5.4 Composite Systems 499
13.6 Other General Requirements 499
13.6.1 Bolted and Welded Connections 499
13.6.2 Protected Zones 500
13.6.3 Local Buckling 500
13.6.4 Column Requirements 500
13.6.5 Column Bases 500
13.7 Conclusions 500
13.8 Problems 500
Multi-Chapter Problem 501
Integrated Design Project 501
Appendix 503
Index
- Example Problems for ANSI/AISC 360-10: All examples have been updated to the new specification and the new table of member properties, as well as being revised to improve clarity of intent.
- New Homework Problems: 60% more homework problems have been added, including problems that carry over from one chapter to another so that an opportunity exists to link concepts of design to one or two specific structures.
- Integrated Design Project: A building is presented in Chapter 1 that is used as an Integrated Design Project throughout the book. This project is different from typical homework problems in that it is a relatively open-ended design project. The Integrated Design Project is available in Chapters 2, 4, 5, 6, 8, 9, 11, 12, and 13. It is presented at the end of the Homework Problems.
- AISC Resources: Chapter 1 has been expanded to include discussion of the three main resources published by AISC that are used throughout this book, the Specification, the Manual, and the AISC web site. It also expands the discussion of reliability and shows that reliability for ASD and LRFD each vary with live-to-dead load ratio although LRFD varies a bit less than ASD.
- Other changes: All Problems use ASCE 7-10, , including new load combinations and approach for determination of wind loads. Chapter 3 addresses changes in ASTM requirements for A992 steel and a new grade of steel for HSS. Chapter 4 uses the new minimum shear lag factor. Chapter 5 addresses torsional restraint at beam supports, new provisions for negative moment redistribution and the new provisions for stem local buckling of tees. New Tables for Small Compression Members are provided for use with chapter 6. Chapter 7 adds coverage of concentrated loads on beam webs and stiffeners. Chapter 11 now addresses beam bearing plates.
- Second-order Effects and Direct Analysis Discussion Expanded: Chapter 8 has seen the greatest revision as new discussion has been included to address the requirements for inclusion of second-order effects and these second-order effects are better integrated into the examples. The revised requirements for use of an amplified first-order analysis are presented. Discussion is expanded on the direct analysis method, the effective length method and the first-order analysis method and an example has been included to address the direct analysis method. A section on combined tension and bending has also been added.
- New Column and Shear Anchor Provisions: Chapter 9 reflects the changes made in the corresponding Chapter I of the Specification.
- New Bolt Strength Used Throughout: Chapters 10, 11, and 12 have been updated to reflect the changes in bolt shear strength and strength of slip critical connections.
- New organization of Seismic Provisions for Structural Steel Buildings: Chapter 13 has been revised to reflect the new organization of ANSI/AISC 341-10 Seismic Provisions for Structural Steel Buildings, and includes several new systems that have been added to the Seismic Provisions.
- Emphasis on determining nominal strength so that an instructor can teach LRFD or ASD or both with little additional effort.
- Every example is completed for both LRFD and ASD with a presentation format that makes the distinction easy to observe.
- Consistent problem-solving procedure: All examples formatted to highlight appropriate steps in the process. Includes consistent problem-solving procedure in examples, to reinforce good problem-solving practices
- LRFD and ASD Homework problems: Homework problems at the end of each chapter are given so that either LRFD or ASD provisions may be assigned.
- Comparing ASD and LRFD:There are also problems designed to show comparisons between ASD and LRFD solutions. These problems will show that in some instances one method might give a more economical design while in other instances the reverse is true.
- U.S. units are used throughout the text.
