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 site soil shall be classified in accordance with Table 20.3-1 and Section 20.3 based on the upper 100 ft (30 m) of the site profile. Where site-specific data are not available to a depth of 100 ft (30 m), appropriate soil properties are permitted to be estimated by the registered design professional preparing the soil investigation report based on known geologic conditions. Where the soil properties are not known in sufficient detail to determine the site class, Site Class D shall be used unless the authority having jurisdiction or geotechnical data determine Site Class E or F soils are present at the site. Site Classes A and B shall not be assigned to a site if there is more than 10 ft (10.1 m) of soil between the rock surface and the bottom of the spread footing or mat foundation.
A site response analysis in accordance with Section 21.1 shall be provided for Site Class F soils, unless the exception to Section 20.3.1 is applicable.
Site class types shall be assigned in accordance with the definitions provided in Table 20.3-1 and this section.
Where any of the following conditions is satisfied, the site shall be classified as Site Class F and a site response analysis in accordance with Section 21.1 shall be performed.
  1. Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable soils, quick and highly sensitive clays, and collapsible weakly cemented soils.
    EXCEPTION: For structures having fundamental periods of vibration equal to or less than 0.5 s, site response analysis is not required to determine spectral accelerations for liquefiable soils. Rather, a site class is permitted to be determined in accordance with Section 20.3 and the corresponding values of Fa and Fv determined from Tables 11.4-1 and 11.4-2.
  1. Peats and/or highly organic clays [H > 10 ft (3 m)] of peat and/or highly organic clay where H = thickness of soil.
  2. Very high plasticity clays [H > 25 ft (7.6 m) with PI > 75].
  3. Very thick soft/medium stiff clays [H > 120 ft (37 m)] with su < 1,000 psf (50 kPa).

Table 20.3-1 Site Classification
Site Class s or ch u
A. Hard rock >5,000 ft/s NA NA
B. Rock 2,500 to 5,000 ft/s NA NA
C. Very dense soil
and soft rock
1,200 to 2,500 ft/s >50 >2,000 psf
D. Stiff soil 600 to 1,200 ft/s 15 to 50 1,000 to 2,000 psf
E. Soft clay soil <600 ft/s <15 <1,000 psf
Any profile with more than 10 ft of soil having
the following characteristics:
—Plasticity index PI > 20,
—Moisture content w ≥ 40%,
—Undrained shear strength su < 500 psf
F. Soils requiring
site response
analysis in
accordance
with Section
21.1
See Section 20.3.1
For SI: 1 ft/s = 0.3048 m/s; 1 lb/ft2 = 0.0479 kN/m2.
Where a site does not qualify under the criteria for Site Class F and there is a total thickness of soft clay greater than 10 ft (3 m) where a soft clay layer is defined by su < 500 psf (25 kPa), w ≥ 40%, and PI > 20, it shall be classified as Site Class E.
The existence of Site Class C, D, and E soils shall be classified by using one of the following three methods with s, , and u computed in all cases as specified in Section 20.4:
  1. s for the top 100 ft (30 m) (s method).
  2. for the top 100 ft (30 m) (N method).
  3. ch for cohesionless soil layers (PI < 20) in the top 100 ft (30 m) and u for cohesive soil layers (PI > 20) in the top 100 ft (30 m) (u method). Where the ch and u criteria differ, the site shall be assigned to the category with the softer soil.
The shear wave velocity for rock, Site Class B, shall be either measured on site or estimated by a geotechnical engineer, engineering geologist, or seismologist for competent rock with moderate fracturing and weathering. Softer and more highly fractured and weathered rock shall either be measured on site for shear wave velocity or classified as Site Class C.
The hard rock, Site Class A, category shall be supported by shear wave velocity measurement either on site or on profiles of the same rock type in the same formation with an equal or greater degree of weathering and fracturing. Where hard rock conditions are known to be continuous to a depth of 100 ft (30 m), surficial shear wave velocity measurements are permitted to be extrapolated to assess s.
The definitions presented in this section shall apply to the upper 100 ft (30 m) of the site profile. Profiles containing distinct soil and rock layers shall be subdivided into those layers designated by a number that ranges from 1 to n at the bottom where there are a total of n distinct layers in the upper 100 ft (30 m). Where some of the n layers are cohesive and others are not, k is the number of cohesive layers and m is the number of cohesionless layers. The symbol i refers to any one of the layers between 1 and n.
s shall be determined in accordance with the following formula:

(20.4-1)

where

di = the thickness of any layer between 0 and 100 ft (30 m)
vsi = the shear wave velocity in ft/s (m/s)
= 100 ft (30 m)
and ch shall be determined in accordance with the following formulas:
(20.4-2)

where Ni and di in Eq. 20.4-2 are for cohesionless soil, cohesive soil, and rock layers.
(20.4-3)

where Ni and di in Eq. 20.4-3 are for cohesionless soil layers only and di = ds where ds is the total thickness of cohesionless soil layers in the top 100 ft (30 m). Ni is the standard penetration resistance (ASTM D1586) not to exceed 100 blows/ft (305 blows/m) as directly measured in the field without corrections. Where refusal is met for a rock layer, Ni shall be taken as 100 blows/ft (305 blows/m) .
u shall be determined in accordance with the following formula:
(20.4-4)

where

= dc
dc = the total thickness of cohesive soil layers in the top 100
ft (30 m)
PI = the plasticity index as determined in accordance with
ASTM D4318
w = the moisture content in percent as determined in accor-
dance with ASTM D2216
sui = the undrained shear strength in psf (kPa), not to exceed
5,000 psf (240 kPa) as determined in accordance with
ASTM D2166 or ASTM D2850
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