About this chapter: Chapter 16 establishes minimum design requirements so that the structural components of buildings are proportioned to resist the loads that are likely to be encountered. In addition, this chapter assigns buildings and structures to risk categories that are indicative of their intended use. The loads specified herein along with the required load combinations have been established through research and service performance of buildings and structures. The application of these loads and adherence to the serviceability criteria enhance the protection of life and property.
Code development reminder: Code change proposals to this chapter will be considered by the IBC—Structural Code Development Committee during the 2022 (Group B) Code Development Cycle.
The following notations are used in this chapter:
|Di||=||Weight of ice in accordance with Chapter 10 of ASCE 7.|
|E||=||Combined effect of horizontal and vertical earthquake induced forces as defined in Section 12.4 of ASCE 7.|
|F||=||Load due to fluids with well-defined pressures and maximum heights.|
|Fa||=||Flood load in accordance with Chapter 5 of ASCE 7.|
|H||=||Load due to lateral earth pressures, ground water pressure or pressure of bulk materials.|
|Lr||=||Roof live load.|
|T||=||Cumulative effects of self-straining load forces and effects.|
|Vasd||=||Allowable stress design wind speed, miles per hour (mph) (km/hr) where applicable.|
|V||=||Basic design wind speeds, miles per hour (mph) (km/hr) determined from Figures 1609.3(1) through 1609.3(12) or ASCE 7.|
|W||=||Load due to wind pressure.|
|Wi||=||Wind-on-ice in accordance with Chapter 10 of ASCE 7.|
Construction documents shall show the size, section and relative locations of structural members with floor levels, column centers and offsets dimensioned. The design loads and other information pertinent to the structural design required by Sections 1603.1.1 through 1603.1.9 shall be indicated on the construction documents.
For buildings located in whole or in part in flood hazard areas as established in Section 1612.3, the documentation pertaining to design, if required in Section 1612.4, shall be included and the following information, referenced to the datum on the community's Flood Insurance Rate Map (FIRM), shall be shown, regardless of whether flood loads govern the design of the building:
Buildings and other structures, and parts thereof, shall be designed and constructed to support safely the factored loads in load combinations defined in this code without exceeding the appropriate strength limit states for the materials of construction. Alternatively, buildings and other structures, and parts thereof, shall be designed and constructed to support safely the nominal loads in load combinations defined in this code without exceeding the appropriate specified allowable stresses for the materials of construction.
DEFLECTION LIMITSa, b, c, h, i
|CONSTRUCTION||L or Lr||S or W f||D + Ld, g|
Supporting plaster or stucco ceiling
Supporting nonplaster ceiling
Not supporting ceiling
With plaster or stucco finishes
With other brittle finishes
With flexible finishes
With plaster or stucco finishes
With other brittle finishes
With flexible finishes
For SI: 1 foot = 304.8 mm.
The deflection of framing members supporting glass subjected to 0.6 times the "component and cladding" wind loads shall not exceed either of the following:
Load effects on structural members and their connections shall be determined by methods of structural analysis that take into account equilibrium, general stability, geometric compatibility and both short- and long-term material properties.
Members that tend to accumulate residual deformations under repeated service loads shall have included in their analysis the effects of added deformations expected to occur during their service life.
Any system or method of construction to be used shall be based on a rational analysis in accordance with well-established principles of mechanics. Such analysis shall result in a system that provides a complete load path capable of transferring loads from their point of origin to the load-resisting elements.
The total lateral force shall be distributed to the various vertical elements of the lateral force-resisting system in proportion to their rigidities, considering the rigidity of the horizontal bracing system or diaphragm. Rigid elements assumed not to be a part of the lateral force-resisting system are permitted to be incorporated into buildings provided that their effect on the action of the system is considered and provided for in the design. A diaphragm is rigid for the purpose of distribution of story shear and torsional moment when the lateral deformation of the diaphragm is less than or equal to two times the average story drift. Where required by ASCE 7, provisions shall be made for the increased forces induced on resisting elements of the structural system resulting from torsion due to eccentricity between the center of application of the lateral forces and the center of rigidity of the lateral force-resisting system.
Every structure shall be designed to resist the effects caused by the forces specified in this chapter, including overturning, uplift and sliding. Where sliding is used to isolate the elements, the effects of friction between sliding elements shall be included as a force.
Each building and structure shall be assigned a risk category in accordance with Table 1604.5. Where a referenced standard specifies an occupancy category, the risk category shall not be taken as lower than the occupancy category specified therein. Where a referenced standard specifies that the assignment of a risk category be in accordance with ASCE 7, Table 1.5-1, Table 1604.5 shall be used in lieu of ASCE 7, Table 1.5-1.
Exception: The assignment of buildings and structures to Tsunami Risk Categories III and IV is permitted to be in accordance with Section 6.4 of ASCE 7.
|RISK CATEGORY||NATURE OF OCCUPANCY|
|I||Buildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to:|
|II||Buildings and other structures except those listed in Risk Categories I, III and IV.|
|III||Buildings and other structures that represent a substantial hazard to human life in the event of failure, including but not limited to:
|IV||Buildings and other structures designated as essential facilities, including but not limited to:
Where a building or structure is occupied by two or more occupancies not included in the same risk category, it shall be assigned the classification of the highest risk category corresponding to the various occupancies. Where buildings or structures have two or more portions that are structurally separated, each portion shall be separately classified. Where a separated portion of a building or structure provides required access to, required egress from or shares life safety components with another portion having a higher risk category, both portions shall be assigned to the higher risk category.
Exception: Where a storm shelter designed and constructed in accordance with ICC 500 is provided in a building, structure or portion thereof normally occupied for other purposes, the risk category for the normal occupancy of the building shall apply unless the storm shelter is a designated emergency shelter in accordance with Table 1604.5.
Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7 Chapters 11, 12, 13, 15, 17 and 18 as applicable, even where wind load effect s are greater than seismic load effects.
Exception: References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein.
Buildings and other structures and portions thereof shall be designed to resist the strength load combinations specified in ASCE 7, Section 2.3, the allowable stress design load combinations specified in ASCE 7, Section 2.4, or the alternative allowable stress design load combinations of Section 1605.2.
In lieu of the load combinations in ASCE 7, Section 2.4, structures and portions thereof shall be permitted to be designed for the most critical effects resulting from the following combinations. Where using these alternative allowable stress load combinations that include wind or seismic loads, allowable stresses are permitted to be increased or load combinations reduced where permitted by the material chapter of this code or the referenced standards. For load combinations that include the counteracting effects of dead and wind loads, only two-thirds of the minimum dead load likely to be in place during a design wind event shall be used. Where using these alternative load combinations to evaluate sliding, overturning and soil bearing at the soil-structure interface, the reduction of foundation overturning from Section 12.13.4 in ASCE 7 shall not be used. Where using these alternative basic load combinations for proportioning foundations for loadings, which include seismic loads, the vertical seismic load effect, Ev, in Equation 12.4-4 of ASCE 7 is permitted to be taken equal to zero. Where required by ASCE 7, Chapters 12, 13 and 15, the load combinations including overstrength of ASCE 7, Section 2.3.6 shall be used.
|OCCUPANCY OR USE||UNIFORM (psf)||CONCENTRATED (pounds)||ALSO SEE SECTION|
|1.||Apartments (see residential)||—||—||—|
|2.||Access floor systems||Office use||50||2,000||—|
|3.||Armories and drill rooms||150b||—||—|
|4.||Assembly areas||Fixed seats (fastened to floor)||60a||—||—|
|Follow spot, projections and control rooms||50|
|Bleachers, folding and telescopic seating and grandstands||100a (See Section 1607.19)|
|Stadiums and arenas with fixed seats (fastened to the floor)||60a (See Section 1607.19)|
|Other assembly areas||100a|
|5.||Balconies and decks||1.5 times the live load for the area served, not required to exceed 100||—||—|
|6.||Catwalks for maintenance and service access||40||300||—|
|Other floors||Same as occupancy served except as indicated|
|9.||Dining rooms and restaurants||100a||—||—|
|10.||Dwellings (see residential)||—||—||—|
|11.||Elevator machine room and control room grating (on area of 2 inches by 2 inches)||—||300||—|
|12.||Finish light floor plate construction (on area of 1 inch by 1 inch)||—||200||—|
|On single-family dwellings only||40|
|14.||Fixed ladders||See Section 1607.17||—|
|15.||Garages||Passenger vehicles only||40c||SeeSection 1607.7||—|
|Trucks and buses||See Section 1607.8|
|16.||Handrails, guards and grab bars||See Section 1607.9||—|
|17.||Helipads||See Section 1607.6||—|
|18.||Hospitals||Corridors above first floor||80||1,000||—|
|Operating rooms, laboratories||60||1,000|
|19.||Hotels (see residential)||—||—||—|
|20.||Libraries||Corridors above first floor||80||1,000||—|
|Stack rooms||150b||1,000||Section 1607.18|
|22.||Marquees, except one- and two-family dwellings||75||—||—|
|23.||Office buildings||Corridors above first floor||80||2,000||—|
|File and computer rooms shall be designed for heavier loads based on anticipated occupancy||—||—|
|Lobbies and first-floor corridors||100||2,000|
|24.||Penal institutions||Cell blocks||40||—||—|
|25.||Recreational uses||Bowling alleys, poolrooms and similar uses||75a||—||—|
|Dance halls and ballrooms||100a|
|Ice skating rinks||250b|
|Roller skating rinks||100a|
|26.||Residential||One- and two-family dwellings:||—||Section 1607.22|
Uninhabitable attics without storage
Uninhabitable attics with storage
All other areas
|Hotels and multifamily dwellings:|
Private rooms and corridors serving them
Public roomsa and corridors serving them
|Ordinary flat, pitched, and curved roofs (that are not occupiable)||20||—|
|Roof areas used for assembly purposes||100a||—|
|Roof areas used for occupancies other than assembly||Same as occupancy served||—|
|Vegetative and landscaped roofs:||—|
Roof areas not intended for occupancy
Roof areas used for assembly purposes
Roof areas used for other occupancies
|Same as occupancy served||—|
|Awnings and canopies:||—|
Fabric construction supported by a skeleton structure
All other construction, except one- and two-family dwellings
|Primary roof members exposed to a work floor:|
All other primary roof members
|All roof surfaces subject to maintenance workers||—||300|
|Corridors above first floor||80||1,000|
|29.||Scuttles, skylight ribs and accessible ceilings||—||200||—|
|30.||Sidewalks, vehicular driveways and yards, subject to trucking||250b||8,000||Section 1607.20|
|31.||Stairs and exits||One- and two-family dwellings||40||300||Section 1607.21|
|All other||100||300||Section 1607.21|
|32.||Storage areas above ceilings||20||—||—|
|33.||Storage warehouses (shall be designed for heavier loads if required for anticipated storage)||Heavy||250b||—||—|
|Wholesale, all floors||125b||1,000|
|35.||Vehicle barriers||See Section 1607.10||—|
|36.||Walkways and elevated platforms (other than exitways)||60||—||—|
|37.||Yards and terraces, pedestrian||100a||—||—|
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2,
1 square foot = 0.0929 m2,
1 pound per square foot = 0.0479 kN/m2, 1 pound = 0.004448 kN,
1 pound per cubic foot = 16 kg/m3.
Landing areas designed for a design basis helicopter with maximum take-off weight of 3,000 pounds (13.35 kN) shall be identified with a 3,000-pound (13.34 kN) weight limitation. The landing area weight limitation shall be indicated by the numeral "3" (kips) located in the bottom right corner of the landing area as viewed from the primary approach path. The indication for the landing area weight limitation shall be a minimum 5 feet (1524 mm) in height.
Where a structure or portions of a structure are accessed and loaded by fire department access vehicles and other similar emergency vehicles, the structure shall be designed for the greater of the following loads:
Garages designed to accommodate vehicles that exceed a 10,000-pound (4536 kg) gross vehicle weight rating, shall be designed using the live loading specified by Section 1607.8.1. For garages the design for impact and fatigue is not required.
Exception: The vehicular live loads and load placement are allowed to be determined using the actual vehicle weights for the vehicles allowed onto the garage floors, provided that such loads and placement are based on rational engineering principles and are approved by the building official, but shall be not less than 50 psf (2.9 kN/m2). This live load shall not be reduced.
For the purpose of design, the weight of machinery and moving loads shall be increased as follows to allow for impact:
Percentages shall be increased where specified by the manufacturer.
In addition to any other applicable live loads, fall arrest, lifeline, and rope descent system anchorages and structural elements that support these anchorages shall be designed for a live load of not less than 3,100 pounds (13.8 kN) for each attached line, in any direction that the load can be applied.
Anchorages of horizontal lifelines and the structural elements that support these anchorages shall be designed for the maximum tension that develops in the horizontal lifeline from these live loads.
Subject to the limitations of Sections 1607.12.1.1 through 1607.12.1.3 and Table 1607.1, members for which a value of KLLAT is 400 square feet (37.16 m2) or more are permitted to be designed for a reduced uniformly distributed live load, L, in accordance with the following equation:
KLL = Live load element factor (see Table 1607.12.1).
AT = Tributary area, in square feet (m2).
L shall be not less than 0.50Lo for members supporting one floor and L shall be not less than 0.40Lo for members supporting two or more floors.
LIVE LOAD ELEMENT FACTOR, KLL
|Exterior columns without cantilever slabs||4|
|Edge columns with cantilever slabs||3|
|Corner columns with cantilever slabs||2|
|Edge beams without cantilever slabs||2|
|Members not previously identified including:||1|
Edge beams with cantilever slabs
Members without provisions for continuous shear transfer normal to their span
Live loads that exceed 100 psf (4.79 kN/m2) shall not be reduced.
As an alternative to Section 1607.12.1 and subject to the limitations of Table 1607.1, uniformly distributed live loads are permitted to be reduced in accordance with the following provisions. Such reductions shall apply to slab systems, beams, girders, columns, piers, walls and foundations.
Ordinary flat, pitched and curved roofs, and awnings and canopies other than of fabric construction supported by a skeleton structure, are permitted to be designed for a reduced uniformly distributed roof live load, Lr, as specified in the following equations or other controlling combinations of loads as specified in Section 1605, whichever produces the greater load effect.
In structures such as greenhouses, where special scaffolding is used as a work surface for workers and materials during maintenance and repair operations, a lower roof load than specified in the following equations shall not be used unless approved by the building official. Such structures shall be designed for a minimum roof live load of 12 psf (0.58 kN/m2).
The reduction factors R1 and R2 shall be determined as follows:
For SI: 1.2 - 0.011 At for 18.58 square meters < At < 55.74 square meters
F = For a sloped roof, the number of inches of rise per foot (for SI: F = 0.12 × slope, with slope expressed as a percentage), or for an arch or dome, the rise-to-span ratio multiplied by 32.
Roof structures that support photovoltaic panel systems shall be designed to resist each of the following conditions:
The maximum wheel loads of the crane shall be increased by the following percentages to account for the effects of vertical impact or vibration:
|Monorail cranes (powered)||25 percent|
|Cab-operated or remotely operated bridge cranes (powered)||25 percent|
|Pendant-operated bridge cranes (powered)||10 percent|
|Bridge cranes or monorail cranes with hand-geared bridge, trolley and hoist||0 percent|
GROUND SNOW LOADS, pg, FOR ALASKAN LOCATIONS
|LOCATION||POUNDS PER SQUARE FOOT|
|St. Paul Islands||40|
For SI: 1 pound per square foot = 0.0479 kN/m2.
Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7. The type of opening protection required, the basic design wind speed, V, and the exposure category for a site is permitted to be determined in accordance with Section 1609 or ASCE 7. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.
The wind speeds in Figures 1609.3(1) through 1609.3(12) are basic design wind speeds, V, and shall be converted in accordance with Section 1609.3.1 to allowable stress design wind speeds, Vasd, when the provisions of the standards referenced in Exceptions 4 and 5 are used.
The provisions of ICC 600 are applicable only to buildings located within Exposure B or C as defined in Section 1609.4. The provisions of ICC 600, AWC WFCM and AISI S230 shall not apply to buildings sited on the upper half of an isolated hill, ridge or escarpment meeting all of the following conditions:
In windborne debris regions, glazing in buildings shall be impact resistant or protected with an impact-resistant covering meeting the requirements of an approved impact-resistant standard or ASTM E1996 referenced herein as follows:
WINDBORNE DEBRIS PROTECTION FASTENING SCHEDULE FOR WOOD STRUCTURAL PANELSa, b, c, d
|FASTENER TYPE||FASTENER SPACING (inches)|
|Panel Span ≤ 4 feet||4 feet < Panel Span ≤ 6 feet||6 feet < Panel ≤ Span 8 feet|
|No. 8 wood-screw-based anchor with 2-inch embedment length||16||10||8|
|No. 10 wood-screw-based anchor with 2-inch embedment length||16||12||9|
|1/4-inch diameter lag-screw-based anchor with 2-inch embedment length||16||16||16|
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.448 N, 1 mile per hour = 0.447 m/s.
The text of Section 6.2.2 of ASTM E1996 shall be substituted as follows:
6.2.2 Unless otherwise specified, select the wind zone based on the basic design wind speed, V, as follows:
22.214.171.124 Wind Zone 1—130 mph ≤ basic design wind speed, V < 140 mph.
126.96.36.199 Wind Zone 2—140 mph ≤ basic design wind speed, V < 150 mph at greater than one mile (1.6 km) from the coastline. The coastline shall be measured from the mean high water mark.
188.8.131.52 Wind Zone 3—150 mph (67 m/s) ≤ basic design wind speed, V ≤ 160 mph (72 m/s), or 140 mph (63 m/s) ≤ basic design wind speed, V ≤ 160 mph (72 m/s) and within one mile (1.6 km) of the coastline. The coastline shall be measured from the mean high water mark.
184.108.40.206 Wind Zone 4— basic design wind speed, V > 160 mph (72 m/s).
The basic design wind speed, V, in mph, for the determination of the wind loads shall be determined by Figures 1609.3(1) through 1609.3(12). The basic design wind speed, V, for use in the design of Risk Category II buildings and structures shall be obtained from Figures 1609.3(1), 1609.3(5) and 1609.3(6). The basic design wind speed, V, for use in the design of Risk Category III buildings and structures shall be obtained from Figures 1609.3(2), 1609.3(7) and 1609.3(8). The basic design wind speed, V, for use in the design of Risk Category IV buildings and structures shall be obtained from Figures 1609.3(3), 1609.3(9) and 1609.3(10). The basic design wind speed, V, for use in the design of Risk Category I buildings and structures shall be obtained from Figures 1609.3(4), 1609.3(11) and 1609.3(12). The basic design wind speed, V, for the special wind regions indicated near mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. The basic design wind speeds, V, determined by the local jurisdiction shall be in accordance with Chapter 26 of ASCE 7.
In nonhurricane-prone regions, when the basic design wind speed, V, is estimated from regional climatic data, the basic design wind speed, V, shall be determined in accordance with Chapter 26 of ASCE 7.
WIND SPEED CONVERSIONSa, b, c
For SI: 1 mile per hour = 0.44 m/s.
A ground surface roughness within each 45-degree (0.79 rad) sector shall be determined for a distance upwind of the site as defined in Section 1609.4.3 from the following categories, for the purpose of assigning an exposure category as defined in Section 1609.4.3.
Surface Roughness C. Open terrain with scattered obstructions having heights generally less than 30 feet (9144 mm). This category includes flat open country, and grasslands.
Surface Roughness D. Flat, unobstructed areas and water surfaces. This category includes smooth mud flats, salt flats and unbroken ice.
An exposure category shall be determined in accordance with the following:
Exposure B. For buildings with a mean roof height of less than or equal to 30 feet (9144 mm), Exposure B shall apply where the ground surface roughness, as defined by Surface Roughness B, prevails in the upwind direction for a distance of not less than 1,500 feet (457 m). For buildings with a mean roof height greater than 30 feet (9144 mm), Exposure B shall apply where Surface Roughness B prevails in the upwind direction for a distance of not less than 2,600 feet (792 m) or 20 times the height of the building, whichever is greater.
Exposure C. Exposure C shall apply for all cases where Exposure B or D does not apply.
Exposure D. Exposure D shall apply where the ground surface roughness, as defined by Surface Roughness D, prevails in the upwind direction for a distance of not less than 5,000 feet (1524 m) or 20 times the height of the building, whichever is greater. Exposure D shall apply where the ground surface roughness immediately upwind of the site is B or C, and the site is within a distance of 600 feet (183 m) or 20 times the building height, whichever is greater, from an Exposure D condition as defined in the previous sentence.
b = Exposed width, feet (mm) of the roof tile.
GCp = Roof pressure coefficient for each applicable roof zone determined from Chapter 30 of ASCE 7. Roof coefficients shall not be adjusted for internal pressure.
L = Length, feet (mm) of the roof tile.
La = Moment arm, feet (mm) from the axis of rotation to the point of uplift on the roof tile. The point of uplift shall be taken at 0.76L from the head of the tile and the middle of the exposed width. For roof tiles with nails or screws (with or without a tail clip), the axis of rotation shall be taken as the head of the tile for direct deck application or as the top edge of the batten for battened applications. For roof tiles fastened only by a nail or screw along the side of the tile, the axis of rotation shall be determined by testing. For roof tiles installed with battens and fastened only by a clip near the tail of the tile, the moment arm shall be determined about the top edge of the batten with consideration given for the point of rotation of the tiles based on straight bond or broken bond and the tile profile.
Ma = Aerodynamic uplift moment, feet-pounds (N-mm) acting to raise the tail of the tile.
qh = Wind velocity pressure, psf (kN/m2) determined from Section 26.10.2 of ASCE 7.
Concrete and clay roof tiles complying with the following limitations shall be designed to withstand the aerodynamic uplift moment as determined by this section.
Foundation walls and retaining walls shall be designed to resist lateral soil loads from adjacent soil. Soil loads specified in Table 1610.1 shall be used as the minimum design lateral soil loads unless determined otherwise by a geotechnical investigation in accordance with Section 1803. Foundation walls and other walls in which horizontal movement is restricted at the top shall be designed for at-rest pressure. Retaining walls free to move and rotate at the top shall be permitted to be designed for active pressure. Lateral pressure from surcharge loads shall be added to the lateral soil load. Lateral pressure shall be increased if expansive soils are present at the site. Foundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections 1805.4.2 and 1805.4.3.
LATERAL SOIL LOAD
|DESCRIPTION OF BACKFILL MATERIALc||UNIFIED SOIL CLASSIFICATION||DESIGN LATERAL SOIL LOADa (pound per square foot per foot of depth)|
|Active pressure||At-rest pressure|
|Well-graded, clean gravels; gravel-sand mixes||GW||30||60|
|Poorly graded clean gravels; gravel-sand mixes||GP||30||60|
|Silty gravels, poorly graded gravel-sand mixes||GM||40||60|
|Clayey gravels, poorly graded gravel-and-clay mixes||GC||45||60|
|Well-graded, clean sands; gravelly sand mixes||SW||30||60|
|Poorly graded clean sands; sand-gravel mixes||SP||30||60|
|Silty sands, poorly graded sand-silt mixes||SM||45||60|
|Sand-silt clay mix with plastic fines||SM-SC||45||100|
|Clayey sands, poorly graded sand-clay mixes||SC||60||100|
|Inorganic silts and clayey silts||ML||45||100|
|Mixture of inorganic silt and clay||ML-CL||60||100|
|Inorganic clays of low to medium plasticity||CL||60||100|
|Organic silts and silt clays, low plasticity||OL||Note b||Note b|
|Inorganic clayey silts, elastic silts||MH||Note b||Note b|
|Inorganic clays of high plasticity||CH||Note b||Note b|
|Organic clays and silty clays||OH||Note b||Note b|
For SI: 1 pound per square foot per foot of depth = 0.157 kPa/m, 1 foot = 304.8 mm.
Each portion of a roof shall be designed to sustain the load of rainwater as per the requirements of Chapter 8 of ASCE 7. The design rainfall shall be based on the 100-year 15-minute duration event, or on other rainfall rates determined from approved local weather data. Alternatively, a design rainfall of twice the 100-year hourly rainfall rate indicated in Figures 1611.1(1) through 1611.1(5) shall be permitted.
For SI: R = 0.0098(ds + dh)
dh = Additional depth of water on the undeflected roof above the inlet of secondary drainage system at its design flow (in other words, the hydraulic head), in inches (mm).
ds = Depth of water on the undeflected roof up to the inlet of secondary drainage system when the primary drainage system is blocked (in other words, the static head), in inches (mm).
R = Rain load on the undeflected roof, in psf (kN/m2). Where the phrase "undeflected roof" is used, deflections from loads (including dead loads) shall not be considered when determining the amount of rain on the roof.
Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with Chapters 11, 12, 13, 15, 17 and 18 of ASCE 7, as applicable. The seismic design category for a structure is permitted to be determined in accordance with Section 1613 or ASCE 7.
Where the soil properties are not known in sufficient detail to determine the site class, Site Class D, subjected to the requirements of Section 1613.2.3, shall be used unless the building official or geotechnical data determines that Site Class E or F soils are present at the site.
Where site investigations that are performed in accordance with Chapter 20 of ASCE 7 reveal rock conditions consistent with Site Class B, but site-specific velocity measurements are not made, the site coefficients Fa and Fv shall be taken at unity (1.0).
1613.2.3 Site Coefficients and Adjusted Maximum Considered Earthquake Spectral Response Acceleration Parameters
The maximum considered earthquake spectral response acceleration for short periods, SMS, and at 1-second period, SM1, adjusted for site class effects shall be determined by Equations 16-20 and 16-21, respectively:
but SMS shall not be taken less than SM1 Except when determining the seismic design caregory in accordance with Section 1613.2.5.
Where Site Class D is selected as the default site class per Section 1613.2.2, the value of Fa shall be not less than 1.2. Where the simplified design procedure of ASCE 7 Section 12.14 is used, the value of Fa shall be determined in accordance with ASCE 7 Section 220.127.116.11, and the values of Fv, SMS and SM1 need not be determined.
VALUES OF SITE COEFFICIENT Faa
|SITE CLASS||MAPPED RISK TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) SPECTRAL RESPONSE ACCELERATION PARAMETER AT SHORT PERIOD|
|Ss ≤ 0.25||Ss = 0.50||Ss = 0.75||Ss = 1.00||Ss = 1.25||Ss ≥ 1.5|
|E||2.4||1.7||1.3||Note b||Note b||Note b|
|F||Note b||Note b||Note b||Note b||Note b||Note b|
VALUES OF SITE COEFFICIENT FVa
|SITE CLASS||MAPPED RISK TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) SPECTRAL RESPONSE ACCELERATION PARAMETER AT 1-SECOND PERIOD|
|S1 ≤ 0.1||S1 = 0.2||S1 = 0.3||S1 = 0.4||S1 = 0.5||S1 ≥ 0.6|
|F||Note b||Note b||Note b||Note b||Note b||Note b|
Five-percent damped design spectral response acceleration at short periods, SDS, and at 1-second period, SD1, shall be determined from Equations 16-22 and Equation 16-23, respectively:
SEISMIC DESIGN CATEGORY BASED ON SHORT-PERIOD (0.2 second) RESPONSE ACCELERATION
|VALUE OF SDS||RISK CATEGORY|
|I or II||III||IV|
|SDS < 0.167g||A||A||A|
|0.167g ≤ SDS < 0.33g||B||B||C|
|0.33g ≤ SDS < 0.50g||C||C||D|
|0.50g ≤ SDS||D||D||D|
Frame structures constructed primarily of reinforced or prestressed concrete, either cast-in-place or precast, or a combination of these, shall conform to the requirements of Section 4.10 of ACI 318. Where ACI 318 requires that nonprestressed reinforcing or prestressing steel pass through the region bounded by the longitudinal column reinforcement, that reinforcing or prestressing steel shall have a minimum nominal tensile strength equal to two-thirds of the required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.
Exception: Where concrete slabs with continuous reinforcement having an area not less than 0.0015 times the concrete area in each of two orthogonal directions are present and are either monolithic with or equivalently bonded to beams, girders or columns, the longitudinal reinforcing or prestressing steel passing through the column reinforcement shall have a nominal tensile strength of one-third of the required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.
1616.2.2 Structural Steel, Open Web Steel Joist or Joist Girder, or Composite Steel and Concrete Frame Structures
End connections of all beams and girders shall have a minimum nominal axial tensile strength equal to the required vertical shear strength for allowable stress design (ASD) or two-thirds of the required shear strength for load and resistance factor design (LRFD) but not less than 10 kips (45 kN). For the purpose of this section, the shear force and the axial tensile force need not be considered to act simultaneously.
Longitudinal ties shall consist of continuous reinforcement in slabs; continuous or spliced decks or sheathing; continuous or spliced members framing to, within or across walls; or connections of continuous framing members to walls. Longitudinal ties shall extend across interior load-bearing walls and shall connect to exterior load-bearing walls and shall be spaced at not greater than 10 feet (3038 mm) on center. Ties shall have a minimum nominal tensile strength, TT, given by Equation 16-24. For ASD the minimum nominal tensile strength shall be permitted to be taken as 1.5 times the allowable tensile stress times the area of the tie.
L = The span of the horizontal element in the direction of the tie, between bearing walls, feet (m).
S = The spacing between ties, feet (m).
αT = A coefficient with a value of 1,500 pounds per foot (2.25 kN/m) for masonry bearing wall structures and a value of 375 pounds per foot (0.6 kN/m) for structures with bearing walls of cold-formed steel light-frame construction.
Perimeter ties shall consist of continuous reinforcement in slabs; continuous or spliced decks or sheathing; continuous or spliced members framing to, within or across walls; or connections of continuous framing members to walls. Ties around the perimeter of each floor and roof shall be located within 4 feet (1219 mm) of the edge and shall provide a nominal strength in tension not less than Tp, given by Equation 16-25. For ASD the minimum nominal tensile strength shall be permitted to be taken as 1.5 times the allowable tensile stress times the area of the tie.