Cover [PDF]

Standards [PDF]

Foreword [PDF]

Acknowledgements [PDF]

Dedication [PDF]

Contents [PDF]

Chapter 1 General

Chapter 2 Combinations of Loads

Chapter 3 Dead Loads, Soil Loads, and Hydrostatic Pressure

Chapter 4 Live Loads

Chapter 5 Flood Loads

Chapter 6 Reserved for Future Provisions

Chapter 7 Snow Loads

Chapter 8 Rain Loads

Chapter 9 Reserved for Future Provisions

Chapter 10 Ice Loads - Atmospheric Icing

Chapter 11 Seismic Design Criteria

Chapter 12 Seismic Design Requirements for Building Structures

Chapter 13 Seismic Design Requirements for Nonstructural Components

Chapter 14 Material Specific Seismic Design and Detailing Requirements

Chapter 15 Seismic Design Requirements for Nonbuilding Structures

Chapter 16 Seismic Response History Procedures

Chapter 17 Seismic Design Requirements for Seismically Isolated Structures

Chapter 18 Seismic Design Requirements for Structures with Damping Systems

Chapter 19 Soil-Structure Interaction for Seismic Design

Chapter 20 Site Classification Procedure for Seismic Design

Chapter 21 Site-Specific Ground Motion Procedures for Seismic Design

Chapter 22 Seismic Ground Motion Long-Period Transition and Risk Coefficient Maps

Chapter 23 Seismic Design Reference Documents

Chapter 24

Chapter 25

Chapter 26 Wind Loads: General Requirements

Chapter 27 Wind Loads on Buildings‒MWFRS (Directional Procedure)

Chapter 28 Wind Loads on Buildings‒MWFRS (Envelope Procedure)

Chapter 29 Wind Loads on Other Structures and Building Appurtenances‒MWFRS

Chapter 30 Wind Loads ‒ Components and Cladding (C&C)

Chapter 31 Wind Tunnel Procedure

Appendix 11A Quality Assurance Provisions

Appendix 11B Existing Building Provisions

Appendix C Serviceability Considerations

Appendix D Buildings Exempted from Torisional Wind Load Cases

The wind tunnel procedure shall be used where required by Sections 27.1.3 , 28.1.3 , and 29.1.3. The wind tunnel procedure shall be permitted for any building or structure in lieu of the design procedures specified in Chapter 27 [MWFRS for buildings of all heights and simple diaphragm buildings with h ≤ 160 ft ( 48.8 m)], Chapter 28 (MWFRS of low-rise buildings and simple diaphragm low-rise buildings), Chapter 29 (MWFRS for all other structures), and Chapter 30 (components and cladding for all building types and other structures).

User Note: Chapter 31 may always be used for determining wind pressures for the MWFRS and/or for C&C of any building or structure. This method is considered to produce the most accurate wind pressures of any method specified in this standard.
Wind tunnel tests, or similar tests employing fluids other than air, used for the determination of design wind loads for any building or other structure, shall be conducted in accordance with this section. Tests for the determination of mean and fluctuating forces and pressures shall meet all of the following conditions:
  1. The natural atmospheric boundary layer has been modeled to account for the variation of wind speed with height.
  2. The relevant macro - (integral) length and micro -length scales of the longitudinal component of atmospheric turbulence are modeled to approximately the same scale as that used to model the building or structure.
  3. The modeled building or other structure and surrounding structures and topography are geometrically similar to their full-scale counterparts, except that for low-rise buildings meeting the requirements of Section 28.1.2 tests shall be permitted for the modeled building in a single exposure site as defined in Section 26.7.3.
  4. The projected area of the modeled building or other structure and surroundings is less than 8% of the test section cross-sectional area unless correction is made for blockage.
  5. The longitudinal pressure gradient in the wind tunnel test section is accounted for.
  6. Reynolds number effects on pressures and forces are minimized.
  7. Response characteristics of the wind tunnel instrumentation are consistent with the required measurements.
Tests for the purpose of determining the dynamic response of a building or other structure shall be in accordance with Section 31.2. The structural model and associated analysis shall account for mass distribution, stiffness, and damping.
The load effect required for strength design shall be determined for the same mean recurrence interval as for the analytical method by using a rational analysis method, defined in the recognized literature, for combining the directional wind tunnel data with the directional meteorological data or probabilistic models based thereon. The load effect required for allowable stress design shall be equal to the load effect required for strength design divided by 1.6. For buildings that are sensitive to possible variations in the values of the dynamic parameters, sensitivity studies shall be required to provide a rational basis for design recommendations .
The wind speeds and probabilistic estimates based thereon shall be subject to the limitations described in Section 26.5.3.
Loads for the main wind-force resisting system determined by wind tunnel testing shall be limited such that the overall principal loads in the x and y directions are not less than 80% of those that would be obtained from Part 1 of Chapter 27 or Part 1 of Chapter 28. The overall principal load shall be based on the overturning moment for flexible buildings and the base shear for other buildings.
     Pressures for components and cladding determined by wind tunnel testing shall be limited to not less than 80% of those calculated for Zone 4 for walls and Zone 1 for roofs using the procedure of Chapter 30. These zones refer to those shown in Figs. 30.4-1, 30.4-2A, 30.4-2B, 30.4-2C, 30.4-3, 30.4-4, 30.4- 5A, 30.4-5B, 30.4-6, 30.4-7, and 30.6-1.
     The limiting value of 80% may be reduced to 50% for the main wind force resisting system and 65% for components and cladding if either of the following conditions applies:
  1. There were no specific influential buildings or objects within the detailed proximity model.
  2. Loads and pressures from supplemental tests for all significant wind directions in which specific influential buildings or objects are replaced by the roughness representative of the adjacent roughness condition, but not rougher than Exposure B, are included in the test results.
Glazing in buildings in wind-borne debris regions shall be protected in accordance with Section 26.10.3.