Asce 7 16 load combinations

Steel Design Project - Civil Engineering

ASCE STANDARD

ASCE/SEI

7-16

Minimum Design Loads and Associated Criteria for Buildings and Other Structures

CHAPTER 2

COMBINATIONS OF LOADS

2.1 GENERAL

Buildings and other structures shall be designed using the provisions of either Section 2.3 or 2.4. Where elements of a structure are designed by a particular material standard or specification, they shall be designed exclusively by either Section 2.3 or 2.4.

2.2 SYMBOLS

Ak = load or load effect arising from extraordinary event A D = dead load Di = weight of ice E = earthquake load F = load caused by fluids with well-defined pressures and

maximum heights Fa = flood load H = load due to lateral earth pressure, ground water pressure, or

pressure of bulk materials L = live load Lr = roof live load N = notional load for structural integrity, Section 1.4 R = rain load S = snow load T = cumulative effect of self-straining forces and effects arising

from contraction or expansion resulting from environmental or operational temperature changes, shrinkage, moisture changes, creep in component materials, movement caused by differential settlement, or combinations thereof

W = wind load Wi = wind-on-ice determined in accordance with Chapter 10

2.3 LOAD COMBINATIONS FOR STRENGTH DESIGN

2.3.1 Basic Combinations. Structures, components, and foundations shall be designed so that their design strength equals or exceeds the effects of the factored loads in the following combinations. Effects of one or more loads not acting shall be considered. Seismic load effects shall be combined loads in accordance with Section 2.3.6. Wind and seismic loads need not be considered to act simultaneously. Refer to Sections 1.4, 2.3.6, 12.4, and 12.14.3 for the specific definition of the earthquake load effect E. Each relevant strength limit state shall be investigated.

1. 1.4D 2. 1.2Dþ 1.6Lþ 0.5(Lr or S or R) 3. 1.2Dþ 1.6(Lr or S or R)þ(L or 0.5W) 4. 1.2Dþ 1.0W þ Lþ 0.5(Lr or S or R) 5. 0.9Dþ 1.0W

EXCEPTIONS:

1. The load factor on L in combinations 3 and 4 is permitted to equal 0.5 for all occupancies in which Lo in Chapter 4, Table 4.3-1, is less than or equal to 100 psf (4.78 kN/sq m), with the exception of garages or areas occupied as places of public assembly.

2. In combinations 2 and 4 the companion load S shall be taken as either the flat roof snow load (pf ) or the sloped roof snow load (ps).

Where fluid loads F are present, they shall be included with the same load factor as dead load D in combinations 1 through 4. Where loads H are present, they shall be included as follows:

1. where the effect of H adds to the principal load effect, include H with a load factor of 1.6;

2. where the effect of H resists the principal load effect, include H with a load factor of 0.9 where the load is permanent or a load factor of 0 for all other conditions.

Effects of one or more loads not acting shall be investigated. The most unfavorable effects from wind loads shall be investi- gated, where appropriate, but they need not be considered to act simultaneously with seismic loads.

Each relevant strength limit state shall be investigated.

2.3.2 Load Combinations Including Flood Load. When a structure is located in a flood zone (Section 5.3.1), the following load combinations shall be considered in addition to the basic combinations in Section 2.3.1:

1. In V-Zones or Coastal A-Zones, 1.0W in combinations 4 and 5 shall be replaced by 1.0W þ 2.0Fa.

2. In noncoastal A-Zones, 1.0W in combinations 4 and 5 shall be replaced by 0.5W þ 1.0Fa

2.3.3 Load Combinations Including Atmospheric Ice Loads. When a structure is subjected to atmospheric ice and wind-on-ice loads, the following load combinations shall be considered:

1. 0.5(Lr or S or R) in combination 2 shall be replaced by 0.2Di þ 0.5S.

2. 1.0W þ 0.5(Lr or S or R) in combination 4 shall be replaced by Di þWi þ 0.5S.

3. 1.0W in combination 5 shall be replaced by Di þWi. 4. 1.0W þ Lþ 0.5(Lr or S or R) in combination 4 shall be

replaced by Di.

2.3.4 Load Combinations Including Self-Straining Forces and Effects. Where the structural effects of T are expected to

Minimum Design Loads and Associated Criteria for Buildings and Other Structures 7

adversely affect structural safety or performance, T shall be considered in combination with other loads. The load factor on T shall be established considering the uncertainty associated with the likely magnitude of the structural forces and effects, the probability that the maximum effect of T will occur simultaneously with other applied loadings, and the potential adverse consequences if the effect of T is greater than assumed. The load factor on T shall not have a value less than 1.0.

2.3.5 Load Combinations for Nonspecified Loads. Where approved by the Authority Having Jurisdiction, the registered design professional is permitted to determine the combined load effect for strength design using a method that is consistent with the method on which the load combination requirements in Section 2.3.1 are based. Such a method must be probability based and must be accompanied by documentation regarding the analysis and collection of supporting data that are acceptable to the Authority Having Jurisdiction.

2.3.6 Basic Combinations with Seismic Load Effects. When a structure is subject to seismic load effects, the following load com- binations shall be considered in addition to the basic combinations in Section 2.3.1. The most unfavorable effects from seismic loads shall be investigated, where appropriate, but they need not be considered to act simultaneously with wind loads.

Where the prescribed seismic load effect, E= f ðEv;EhÞ (defined in Section 12.4.2 or 12.14.3.1) is combined with the effects of other loads, the following seismic load combinations shall be used:

6. 1.2Dþ Ev þ Eh þ Lþ 0.2S 7. 0.9D − Ev þ Eh Where the seismic load effect with overstrength,

Em = f ðEv;EmhÞ, defined in Section 12.4.3, is combined with the effects of other loads, the following seismic load combination for structures shall be used:

6. 1.2Dþ Ev þ Emh þ Lþ 0.2S 7. 0.9D − Ev þ Emh

EXCEPTION:

1. The load factor on L in combinations 6 is permitted to equal 0.5 for all occupancies in which Lo in Chapter 4, Table 4.3-1, is less than or equal to 100 psf (4.78 kN/sqm), with the exception of garages or areas occupied as places of public assembly.

2. In combinations 6, the companion load S shall be taken as either the flat roof snow load (pf ) or the sloped roof snow load (ps).

Where fluid loads F are present, they shall be included with the same load factor as dead load D in combinations 6 and 7.

Where loads H are present, they shall be included as follows:

1. Where the effect of H adds to the primary variable load effect, include H with a load factor of 1.6;

2. Where the effect of H resists the primary variable load effect, include H with a load factor of 0.9 where the load is permanent or a load factor of 0 for all other conditions.

2.4 LOAD COMBINATIONS FOR ALLOWABLE STRESS DESIGN

2.4.1 Basic Combinations. Loads listed herein shall be con- sidered to act in the following combinations; whichever produces the most unfavorable effect in the building, foundation, or structural member shall be considered. Effects of one or more loads not acting shall be considered. Seismic load effects shall be

combined with other loads in accordance with Section 2.4.5. Wind and seismic loads need not be considered to act simultaneously. Refer to Sections 1.4, 2.4.5, 12.4, and 12.14.3 for the specific definition of the earthquake load effect E.

Increases in allowable stress shall not be used with the loads or load combinations given in this standard unless it can be demonstrated that such an increase is justified by structural behavior caused by rate or duration of load.

1. D 2. Dþ L 3. Dþ (Lr or S or R) 4. Dþ 0.75Lþ 0.75(Lr or S or R) 5. Dþ ð0.6WÞ 6. Dþ 0.75Lþ 0.75ð0.6WÞ þ 0.75(Lr or S or R) 7. 0.6Dþ 0.6W

EXCEPTIONS:

1. In combinations 4 and 6, the companion load S shall be taken as either the flat roof snow load (pf ) or the sloped roof snow load (ps).

2. For nonbuilding structures in which the wind load is deter- mined from force coefficients,Cf , identified in Figs. 29.4-1, 29.4-2, and 29.4-3 and the projected area contributing wind force toa foundationelement exceeds1,000 sq ft (93 sqm)on either a vertical or a horizontal plane, it shall be permitted to replace W with 0.9W in combination 7 for design of the foundation, excluding anchorage of the structure to the foundation.

Where fluid loads F are present, they shall be included in combinations 1 through 6 with the same factor as that used for dead load D.

Where loads H are present, they shall be included as follows:

1. where the effect of H adds to the principal load effect, include H with a load factor of 1.0;

2. where the effect of H resists the principal load effect, include H with a load factor of 0.6 where the load is permanent or a load factor of 0 for all other conditions.

The most unfavorable effects from both wind and earthquake loads shall be considered, where appropriate, but they need not be assumed to act simultaneously. Refer to Sections 1.4, 2.4.5, 12.4, and 12.14.3 for the specific definition of the earthquake load effect E.

Increases in allowable stress shall not be used with the loads or load combinations given in this standard unless it can be demonstrated that such an increase is justified by structural behavior caused by rate or duration of load.

2.4.2 Load Combinations Including Flood Load. When a structure is located in a flood zone, the following load combinations shall be considered in addition to the basic combinations in Section 2.4.1:

1. In V-Zones or Coastal A-Zones (Section 5.3.1), 1.5Fa shall be added to other loads in combinations 5, 6, and 7, and E shall be set equal to zero in combinations 5 and 6.

2. In noncoastal A-Zones, 0.75Fa shall be added to combina- tions 5, 6, and 7, and E shall be set equal to zero in combinations 5 and 6.

2.4.3 Load Combinations Including Atmospheric Ice Loads. When a structure is subjected to atmospheric ice and wind-on-ice loads, the following load combinations shall be considered:

1. 0.7Di shall be added to combination 2.

8 STANDARD ASCE/SEI 7-16

2. (Lr or S or R) in combination 3 shall be replaced by 0.7Di þ 0.7Wi þ S.

3. 0.6W in combination 7 shall be replaced by 0.7Di þ 0.7Wi. 4. 0.7Di shall be added to combination 1.

2.4.4 Load Combinations Including Self-Straining Forces and Effects. Where the structural effects of T are expected to adversely affect structural safety or performance, T shall be considered in combination with other loads. Where the maximum effect of load T is unlikely to occur simultaneously with the maximum effects of other variable loads, it shall be permitted to reduce the magnitude of T considered in combination with these other loads. The fraction of T considered in combination with other loads shall not be less than 0.75.

2.4.5 Basic Combinations with Seismic Load Effects. When a structure is subject to seismic load effects, the following load combinations shall be considered in addition to the basic combinations and associated Exceptions in Section 2.4.1.

Where the prescribed seismic load effect, E= f ðEv;EhÞ (de- fined in Section 12.4.2) is combined with the effects of other loads, the following seismic load combinations shall be used:

8. 1.0Dþ 0.7Ev þ 0.7Eh 9. 1.0Dþ 0.525Ev þ 0.525Eh þ 0.75Lþ 0.75S

10. 0.6D − 0.7Ev þ 0.7Eh Where the seismic load effect with overstrength,

Em = f ðEv;EmhÞ, defined in Section 12.4.3, is combined with the effects of other loads, the following seismic load combination for structures not subject to flood or atmospheric ice loads shall be used:

8. 1.0Dþ 0.7Ev þ 0.7Emh 9. 1.0Dþ 0.525Ev þ 0.525Emh þ 0.75Lþ 0.75S

10. 0.6D − 0.7Ev þ 0.7Emh Where allowable stress design methodologies are used with

the seismic load effect defined in Section 12.4.3 and applied in load combinations 8, 9, or 10, allowable stresses are permitted to be determined using an allowable stress increase factor of 1.2. This increase shall not be combined with increases in allowable stresses or load combination reductions otherwise permitted by this standard or the material reference document except for increases caused by adjustment factors in accordance with AWC NDS.

EXCEPTIONS:

1. In combinations 9, the companion load S shall be taken as either the flat roof snow load (pf ) or the sloped roof snow load (ps).

2. It shall be permitted to replace 0.6D with 0.9D in combi- nation 10 for the design of special reinforced masonry shear walls where the walls satisfy the requirement of Section 14.4.2.

Where fluid loads F are present, they shall be included in combinations 8, 9, and 10 with the same factor as that used for dead load D.

Where loads H are present, they shall be included as follows:

1. where the effect of H adds to the primary variable load effect, include H with a load factor of 1.0;

2. where the effect of H resists the primary variable load effect, include H with a load factor of 0.6 where the load is permanent or a load factor of 0 for all other conditions.

2.5 LOAD COMBINATIONS FOR EXTRAORDINARY EVENTS

2.5.1 Applicability. Where required by the owner or applicable code, strength and stability shall be checked to ensure that structures are capable of withstanding the effects of extra- ordinary (i.e., low-probability) events, such as fires, explo- sions, and vehicular impact without disproportionate collapse.

2.5.2 Load Combinations.

2.5.2.1 Capacity. For checking the capacity of a structure or structural element to withstand the effect of an extraordinary event, the following gravity load combination shall be considered:

ð0.9 or 1.2ÞDþ Ak þ 0.5Lþ 0.2S (2.5-1) in which Ak = the load or load effect resulting from extraordinary event A.

2.5.2.2 Residual Capacity. For checking the residual load- carrying capacity of a structure or structural element following the occurrence of a damaging event, selected load-bearing elements identified by the registered design professional shall be notionally removed, and the capacity of the damaged structure shall be evaluated using the following gravity load combination:

ð0.9 or 1.2ÞDþ 0.5Lþ 0.2ðLr or S or RÞ (2.5-2)

2.5.3 Stability Requirements. Stability shall be provided for the structure as a whole and for each of its elements. Any method that considers the influence of second-order effects is permitted.

2.6 LOAD COMBINATIONS FOR GENERAL STRUCTURAL INTEGRITY LOADS

The notional loads, N, specified in Section 1.4 for structural integrity shall be combined with other loads in accordance with Section 2.6.1 for strength design and Section 2.6.2 for allowable stress design.

2.6.1 Strength Design Notional Load Combinations.

1. 1.2Dþ 1.0N þ Lþ 0.2S 2. 0.9Dþ 1.0N

2.6.2 Allowable Stress Design Notional Load Combinations.

1. Dþ 0.7N 2. Dþ 0.75ð0.7NÞ þ 0.75Lþ 0.75(Lr or S or R) 3. 0.6Dþ 0.7N

2.7 CONSENSUS STANDARDS AND OTHER REFERENCED DOCUMENTS

This section lists the consensus standards and other documents that shall be considered part of this standard to the extent referenced in this chapter.

ANSI/AISC 300, Specification for Structural Steel Buildings, American Institute of Steel Construction, 2016.

Cited in: Section 2.3.5 AWC NDS 12, National Design Specification for Wood Con-

struction, Including Supplements, AmericanWood Council, 2012. Cited in: Section 2.4.5 AWC NDS 15, National Design Specification for Wood Con-

struction, Including Supplements, AmericanWood Council, 2014. Cited in: Section 2.4.5

Minimum Design Loads and Associated Criteria for Buildings and Other Structures 9

CHAPTER 4

LIVE LOADS

4.1 DEFINITIONS

The following definitions apply to the provisions of this chapter. FIXED LADDER: A ladder that is permanently attached to a

structure, building, or equipment. GRAB BAR SYSTEM: A bar and associated anchorages and

attachments to the structural system, for the support of body weight in locations such as toilets, showers, and tub enclosures.

GUARDRAIL SYSTEM: A system of components, includ- ing anchorages and attachments to the structural system, near open sides of an elevated surface for the purpose of minimizing the possibility of a fall from the elevated surface by people, equipment, or material.

HANDRAIL SYSTEM: A rail grasped by hand for guidance and support and associated anchorages and attachments to the structural system.

HELIPAD: A structural surface that is used for landing, taking off, taxiing, and parking of helicopters.

LIVE LOAD: A load produced by the use and occupancy of the building or other structure that does not include construction or environmental loads, such as wind load, snow load, rain load, earthquake load, flood load, or dead load.

ROOF LIVE LOAD: A load on a roof produced (1) during maintenance by workers, equipment, and materials, and (2) dur- ing the life of the structure by movable objects, such as planters or other similar small decorative appurtenances that are not occupancy related. An occupancy-related live load on a roof such as rooftop assembly areas, rooftop decks, and vegetative or landscaped roofs with occupiable areas, is considered to be a live load rather than a roof live load.

SCREEN ENCLOSURE: A building or part thereof, in whole or in part self-supporting, having walls and a roof of insect or sun screening using fiberglass, aluminum, plastic, or similar lightweight netting material, which encloses an occupan- cy or use such as outdoor swimming pools, patios or decks, and horticultural and agricultural production facilities.

VEHICLE BARRIER SYSTEM: A system of components, including anchorages and attachments to the structural system near open sides or walls of garage floors or ramps, that acts as a restraint for vehicles.

4.2 LOADS NOT SPECIFIED

For occupancies or uses not designated in this chapter, the live load shall be determined in accordance with a method approved by the Authority Having Jurisdiction.

4.3 UNIFORMLY DISTRIBUTED LIVE LOADS

4.3.1 Required Live Loads. The live loads used in the design of buildings and other structures shall be the maximum loads expected by the intended use or occupancy but shall in no case be

less than the minimum uniformly distributed unit loads required by Table 4.3-1.

4.3.2 Provision for Partitions. In office buildings and in other buildings where partition locations are subject to change, provisions for partition weight shall be made, whether or not partitions are shown on the plans. The partition load shall not be less than 15 psf (0.72 kN∕m2).

EXCEPTION: A partition live load is not required where the minimum specified live load is 80 psf (3.83 kN∕m2) or greater.

4.3.3 Partial Loading. The full intensity of the appropriately reduced live load applied only to a portion of a structure or member shall be accounted for if it produces a more unfavorable load effect than the same intensity applied over the full structure or member. Roof live loads shall be distributed as specified in Table 4.3-1.

4.4 CONCENTRATED LIVE LOADS

Floors, roofs, and other similar surfaces shall be designed to support the uniformly distributed live loads prescribed in Section 4.3 or the concentrated load, in pounds or kilonewtons (kN), given in Table 4.3-1, whichever produces the greater load effects. Unless otherwise specified, the indicated concentration shall be assumed to be uniformly distributed over an area 2.5 ft (762 mm) by 2.5 ft (762 mm) and shall be located so as to produce the maximum load effects in the members.

4.5 LOADS ON HANDRAIL, GUARDRAIL, GRAB BAR, AND VEHICLE BARRIER SYSTEMS, AND ON FIXED LADDERS

4.5.1 Handrail and Guardrail Systems. Handrail and guardrail systems shall be designed to resist a single concentrated load of 200 lb (0.89 kN) applied in any direction at any point on the handrail or top rail to produce the maximum load effect on the element being considered and to transfer this load through the supports to the structure.

4.5.1.1 Uniform Load. Handrail and guardrail systems shall also be designed to resist a load of 50 lb∕ft (pound-force per linear foot) (0.73 kN∕m) applied in any direction along the handrail or top rail and to transfer this load through the supports to the structure. This load need not be assumed to act concurrently with the concentrated load specified in Section 4.5.1.

EXCEPTIONS: The uniform load need not be considered for the following occupancies:

1. one- and two-family dwellings, and 2. factory, industrial, and storage occupancies in areas that are

not accessible to the public and that serve an occupant load not greater than 50.

Minimum Design Loads and Associated Criteria for Buildings and Other Structures 13

Table 4.3-1 Minimum Uniformly Distributed Live Loads, Lo , and Minimum Concentrated Live Loads

Occupancy or Use Uniform, Lo psf (kN∕m2)

Live Load Reduction Permitted?

(Sec. No.)

Multiple-Story Live Load Reduction

Permitted? (Sec. No.) Concentrated

lb (kN) Also See Section

Apartments (See Residential) Access floor systems

Office use 50 (2.40) Yes (4.7.2) Yes (4.7.2) 2,000 (8.90) Computer use 100 (4.79) Yes (4.7.2) Yes (4.7.2) 2,000 (8.90)

Armories and drill rooms 150 (7.18) No (4.7.5) No (4.7.5) Assembly areas

Fixed seats (fastened to floors) 60 (2.87) No (4.7.5) No (4.7.5) Lobbies 100 (4.79) No (4.7.5) No (4.7.5) Movable seats 100 (4.79) No (4.7.5) No (4.7.5) Platforms (assembly) 100 (4.79) No (4.7.5) No (4.7.5) Stage floors 150 (7.18) No (4.7.5) No (4.7.5) Reviewing stands, grandstands, and

bleachers 100 (4.79) No (4.7.5) No (4.7.5) 4.14

Stadiums and arenas with fixed seats (fastened to the floor)

60 (2.87) No (4.7.5) No (4.7.5) 4.14

Other assembly areas 100 (4.79) No (4.7.5) No (4.7.5) Balconies and decks 1.5 times the live load for the

area served. Not required to exceed 100 psf (4.79 kN∕m2)

Yes (4.7.2) Yes (4.7.2)

Catwalks for maintenance access 40 (1.92) Yes (4.7.2) Yes (4.7.2) 300 (1.33) Corridors

First floor 100 (4.79) Yes (4.7.2) Yes (4.7.2) Other floors Same as occupancy served

except as indicated Dining rooms and restaurants 100 (4.79) No (4.7.5) No (4.7.5) Dwellings (See Residential) Elevator machine room grating (on area of

2 in. by 2 in. (50 mm by 50 mm)) — — 300 (1.33)

Finish light floor plate construction (on area of 1 in. by 1 in. (25 mm by 25 mm))

— — 200 (0.89)

Fire escapes 100 (4.79) Yes (4.7.2) Yes (4.7.2) On single-family dwellings only 40 (1.92) Yes (4.7.2) Yes (4.7.2)

Fixed ladders — — See Sec. 4.5.4 Garages (See Section 4.10)

Passenger vehicles only 40 (1.92) No (4.7.4) Yes (4.7.4) See Sec. 4.10.1 Trucks and buses See Sec. 4.10.2 — — See Sec. 4.10.2

Handrails and Guardrails See Sec. 4.5.1 — — See Sec. 4.5.1 Grab bars — — See Sec. 4.5.2

Helipads (See Section 4.11) Helicopter takeoff weight 3,000 lb

(13.35 kN) or less 40 (1.92) No (4.11.1) — See Sec. 4.11.2

Helicopter takeoff weight more than 3,000 lb (13.35 kN)

60 (2.87) No (4.11.1) — See Sec. 4.11.2

Hospitals Operating rooms, laboratories 60 (2.87) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45) Patient rooms 40 (1.92) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45) Corridors above first floor 80 (3.83) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45)

Hotels (See Residential) Libraries

Reading rooms 60 (2.87) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45) Stack rooms 150 (7.18) No (4.7.3) Yes (4.7.3) 1,000 (4.45) 4.13 Corridors above first floor 80 (3.83) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45)

Manufacturing Light 125 (6.00) No (4.7.3) Yes (4.7.3) 2,000 (8.90) Heavy 250 (11.97) No (4.7.3) Yes (4.7.3) 3,000 (13.35)

Office buildings File and computer rooms shall be designed

for heavier loads based on anticipated occupancy

Lobbies and first-floor corridors 100 (4.79) Yes (4.7.2) Yes (4.7.2) 2,000 (8.90) Offices 50 (2.40) Yes (4.7.2) Yes (4.7.2) 2,000 (8.90) Corridors above first floor 80 (3.83) Yes (4.7.2) Yes (4.7.2) 2,000 (8.90)

continues

14 STANDARD ASCE/SEI 7-16

Table 4.3-1. (Continued) Minimum Uniformly Distributed Live Loads, Lo , and Minimum Concentrated Live Loads

Occupancy or Use Uniform, Lo psf (kN∕m2)

Live Load Reduction Permitted?

(Sec. No.)

Multiple-Story Live Load Reduction

Permitted? (Sec. No.) Concentrated

lb (kN) Also See Section

Penal institutions Cell blocks 40 (1.92) Yes (4.7.2) Yes (4.7.2) Corridors 100 (4.79) Yes (4.7.2) Yes (4.7.2)

Recreational uses Bowling alleys, poolrooms, and similar

uses 75 (3.59) No (4.7.5) No (4.7.5)

Dance halls and ballrooms 100 (4.79) No (4.7.5) No (4.7.5) Gymnasiums 100 (4.79) No (4.7.5) No (4.7.5)

Residential One- and two-family dwellings

Uninhabitable attics without storage 10 (0.48) Yes (4.7.2) Yes (4.7.2) 4.12.1 Uninhabitable attics with storage 20 (0.96) Yes (4.7.2) Yes (4.7.2) 4.12.2 Habitable attics and sleeping areas 30 (1.44) Yes (4.7.2) Yes (4.7.2) All other areas except stairs 40 (1.92) Yes (4.7.2) Yes (4.7.2)

All other residential occupancies Private rooms and corridors serving

them 40 (1.92) Yes (4.7.2) Yes (4.7.2)

Public rooms 100 (4.79) No (4.7.5) No (4.7.5) Corridors serving public rooms 100 (4.79) Yes (4.7.2) Yes (4.7.2)

Roofs Ordinary flat, pitched, and curved roofs 20 (0.96) Yes (4.8.2) — 4.8.1 Roof areas used for occupants Same as occupancy served Yes (4.8.3) — Roof areas used for assembly purposes 100 (4.70) Yes (4.8.3) Vegetative and landscaped roofs

Roof areas not intended for occupancy 20 (0.96) Yes (4.8.2) — Roof areas used for assembly purposes 100 (4.70) Yes (4.8.3) — Roof areas used for other occupancies Same as occupancy served Yes (4.8.3) —

Awnings and canopies Fabric construction supported by a

skeleton structure 5 (0.24) No (4.8.2) —

Screen enclosure support frame 5 (0.24) based on the tributary area of the roof supported by the frame member

No (4.8.2) — 200 (0.89)

All other construction 20 (0.96) Yes (4.8.2) — 4.8.1 Primary roof members, exposed to a work floor Single panel point of lower chord of roof 2,000 (8.90)

trusses or any point along primary structural members supporting roofs over manufacturing, storage warehouses, and repair garages

All other primary roof members — — 300 (1.33) All roof surfaces subject to maintenance

workers — — 300 (1.33)

Schools Classrooms 40 (1.92) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45) Corridors above first floor 80 (3.83) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45) First-floor corridors 100 (4.79) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45)

Scuttles, skylight ribs, and accessible ceilings

200 (0.89)

Sidewalks, vehicular driveways, and yards subject to trucking

250 (11.97) No (4.7.3) Yes (4.7.3) 8,000 (35.60) 4.15

Stairs and exit ways 100 (4.79) Yes (4.7.2) Yes (4.7.2) 300 (1.33) 4.16 One- and two-family dwellings only 40 (1.92) Yes (4.7.2) Yes (4.7.2) 300 (1.33) 4.16

Storage areas above ceilings 20 (0.96) Yes (4.7.2) Yes (4.7.2) Storage warehouses (shall be designed for

heavier loads if required for anticipated storage) Light 125 (6.00) No (4.7.3) Yes (4.7.3) Heavy 250 (11.97) No (4.7.3) Yes (4.7.3)

continues

Minimum Design Loads and Associated Criteria for Buildings and Other Structures 15

4.5.1.2 Guardrail System Component Loads. Balusters, panel fillers, and guardrail infill components, including all rails except the handrail and the top rail, shall be designed to resist a horizontally applied normal load of 50 lb (0.22 kN) on an area not to exceed 12 in. by 12 in. (305 mm by 305 mm), including openings and space between rails and located so as to produce the maximum load effects. Reactions due to this loading are not required to be superimposed with the loads specified in Sections 4.5.1 and 4.5.1.1.

4.5.2 Grab Bar Systems. Grab bar systems shall be designed to resist a single concentrated load of 250 lb (1.11 kN) applied in any direction at any point on the grab bar to produce the maximum load effect.

4.5.3 Vehicle Barrier Systems. Vehicle barrier systems for passenger vehicles shall be designed to resist a single load of 6,000 lb (26.70 kN) applied horizontally in any direction to the barrier system and shall have anchorages or attachments capable of transferring this load to the structure. For design of the system, the load shall be assumed to act at heights between 1 ft 6 in. (460 mm) and 2 ft 3 in. (686 mm) above the floor or ramp surface, located to produce the maximum load effects. The load shall be applied on an area not to exceed 12 in. by 12 in. (305 mm by 305 mm). This load is not required to act concurrently with any handrail or guardrail system loadings specified in Section 4.5.1. Vehicle barrier systems in garages accommodating trucks and buses shall be designed in accordance with AASHTO LRFD Bridge Design Specifications.

4.5.4 Fixed Ladders. Fixed ladders with rungs shall be designed to resist a single concentrated load of 300 lb (1.33 kN) applied at any point to produce the maximum load effect on the element being considered. The number and position of additional concentrated live load units shall be a minimum of 1 unit of 300 lb (1.33 kN) for every 10 ft (3.05 m) of ladder height.

Where rails of fixed ladders extend above a floor or platform at the top of the ladder, each side rail extension shall be designed to resist a single concentrated live load of 100 lb (0.445 kN) applied in any direction at any height up to the top of the side rail extension. Ships ladders with treads instead of rungs shall be designed to resist the stair loads given in Table 4.3-1.

4.6 IMPACT LOADS

4.6.1 General. The live loads specified in Sections 4.3 through 4.5 shall be assumed to include adequate allowance for ordinary

impact conditions. Provision shall be made in the structural design for uses and loads that involve unusual vibration and impact forces.

4.6.2 Elevators. All elements subject to dynamic loads from elevators shall be designed for impact loads and deflection limits prescribed by ASME A17.

4.6.3 Machinery. For the purpose of design, the weight of machinery and moving loads shall be increased as follows to allow for impact: (1) light machinery, shaft- or motor-driven, 20%; and (2) reciprocating machinery or power-driven units, 50%. All percentages shall be increased where specified by the manufacturer.

4.6.4 Elements Supporting Hoists for Façade Access and Building Maintenance Equipment. Structural elements that support hoists for façade and building maintenance equipment shall be designed for a live load of 2.5 times the rated load of the hoist or the stall load of the hoist, whichever is larger.

4.6.5 Fall Arrest and Lifeline Anchorages. Fall arrest and lifeline anchorages and structural elements that support these anchorages shall be designed for a live load of 3,100 lb (13.8 kN) for each attached lifeline in every direction that a fall arrest load may be applied.

4.7 REDUCTION IN UNIFORM LIVE LOADS

4.7.1 General. Except for roof uniform live loads, all other minimum uniformly distributed live loads, Lo in Table 4.3-1, are permitted to be reduced in accordance with the requirements of Sections 4.7.2 through 4.7.6.

4.7.2 Reduction in Uniform Live Loads. Subject to the limitations of Sections 4.7.3 through 4.7.6, members for which a value of KLLAT is 400 ft2 (37.16 m2) or more are permitted to be designed for a reduced live load in accordance with the following formula:

L= Lo

� 0.25þ 15ffiffiffiffiffiffiffiffiffiffiffiffiffi

KLLAT p

� (4.7-1)

L= Lo

� 0.25þ 4.57ffiffiffiffiffiffiffiffiffiffiffiffiffi

KLLAT p

� (4.7-1si)

Table 4.3-1. (Continued) Minimum Uniformly Distributed Live Loads, Lo , and Minimum Concentrated Live Loads

Occupancy or Use Uniform, Lo psf (kN∕m2)

Live Load Reduction Permitted?

(Sec. No.)

Multiple-Story Live Load Reduction

Permitted? (Sec. No.) Concentrated

lb (kN) Also See Section

Stores Retail

First floor 100 (4.79) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45) Upper floors 75 (3.59) Yes (4.7.2) Yes (4.7.2) 1,000 (4.45)

Wholesale, all floors 125 (6.00) No (4.7.3) Yes (4.7.3) 1,000 (4.45) Vehicle barriers See Sec. 4.5.3 Walkways and elevated platforms (other

than exit ways) 60 (2.87) Yes (4.7.2) Yes (4.7.2)

Yards and terraces, pedestrian 100 (4.79) No (4.7.5) No (4.7.5)

16 STANDARD ASCE/SEI 7-16

where

L = reduced design live load per ft2 (m2) of area supported by the member

Lo = unreduced design live load per ft2 (m2) of area supported by the member (see Table 4.3-1)

KLL = live load element factor (see Table 4.7-1) AT = tributary area in ft2 (m2).

L shall not be less than 0.50Lo for members supporting one floor, and L shall not be less than 0.40Lo for members supporting two or more floors.

4.7.3 Heavy Live Loads. Live loads that exceed 100 lb∕ft2 (4.79 kN∕m2) shall not be reduced.

EXCEPTION: Live loads for members supporting two or more floors are permitted to be reduced by a maximum of 20%, but the reduced live load shall not be less than L as calculated in Section 4.7.2.

4.7.4 Passenger Vehicle Garages. The live loads shall not be reduced in passenger vehicle garages.

EXCEPTION: Live loads for members supporting two or more floors are permitted to be reduced by a maximum of 20%, but the reduced live load shall not be less than L as calculated in Section 4.7.2.

4.7.5 Assembly Uses. Live loads shall not be reduced in assembly uses.

4.7.6 Limitations on One-Way Slabs. The tributary area, AT , for one-way slabs shall not exceed an area defined by the slab span times a width normal to the span of 1.5 times the slab span.

4.8 REDUCTION IN ROOF LIVE LOADS

4.8.1 General. The minimum uniformly distributed roof live loads, Lo in Table 4.3-1, are permitted to be reduced in accordance with the requirements of Sections 4.8.2 and 4.8.3.

Where uniform roof live loads are reduced to less than 20 lb∕ft2 (0.96 kN∕m2) in accordance with Section 4.8.2 and are applied to the design of structural members arranged so as to create continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans, whichever produces the greatest unfavorable load effect.

4.8.2 Ordinary Roofs, Awnings, and Canopies. Ordinary flat, pitched, and curved roofs, and awning and canopies other than

those of fabric construction supported by a skeleton structure, are permitted to be designed for a reduced roof live load, as specified in Eq. (4.8-1), or other controlling combinations of loads, as specified in Chapter 2, 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 Eq. (4.8-1) shall not be used unless approved by the Authority Having Jurisdiction. On such structures, the minimum roof live load shall be 12 psf (0.58 kN∕m2).

Lr =LoR1R2 where 12 ≤ Lr ≤ 20 (4.8-1)

Lr = LoR1R2 where 0.58 ≤ Lr ≤ 0.96 (4.8-1si)

where

Lr = reduced roof live load per ft2 (m2) of horizontal projection supported by the member and

Lo = unreduced design roof live load per ft2 (m2) of horizontal projection supported by the member (see Table 4.3-1).

The reduction factors R1 and R2 shall be determined as follows:

R1 = 1 for AT ≤ 200 ft2 1.2 − 0.001AT for 200 ft2 < AT < 600 ft2 0.6 for AT ≥ 600 ft2

in SI:

R1 = 1 for AT ≤ 18.58 m2 1.2 − 0.011AT for 18.58 m2 < AT < 55.74 m2 0.6 for AT ≥ 55.74 m2

where AT = tributary area in ft2 (m2) supported by the member and

R2 = 1 for F ≤ 4 1.2 − 0.05F for 4 < F < 12 0.6 for F ≥ 12

where, for a pitched roof, F = number of inches of rise per foot (in SI: F = 0.12 × slope, with slope expressed in percentage points) and, for an arch or dome, F = rise-to-span ratio multiplied by 32.

4.8.3 Occupiable Roofs. Roofs that have an occupancy function, such as roof gardens or other special purposes, are permitted to have their uniformly distributed live load reduced in accordance with the requirements of Section 4.7.

Roofs used for other special purposes shall be designed for appropriate loads as approved by the Authority Having Jurisdiction.

4.9 CRANE LOADS

4.9.1 General. The crane live load shall be the rated capacity of the crane. Design loads for the runway beams, including connections and support brackets, of moving bridge cranes and monorail cranes shall include the maximum wheel loads

Table 4.7-1 Live Load Element Factor, KLL

Element KLL a

Interior columns 4 Exterior columns without cantilever slabs 4 Edge columns with cantilever slabs 3 Corner columns with cantilever slabs 2 Edge beams without cantilever slabs 2 Interior beams 2 All other members not identified, including 1

Edge beams with cantilever slabs Cantilever beams One-way slabs Two-way slabs Members without provisions for continuous shear

transfer normal to their span

aIn lieu of the preceding values, KLL is permitted to be calculated.

Minimum Design Loads and Associated Criteria for Buildings and Other Structures 17

CHAPTER 26

WIND LOADS: GENERAL REQUIREMENTS

26.1 PROCEDURES

26.1.1 Scope. Buildings and other structures, including themain wind force resisting system (MWFRS) and all components and cladding (C&C) thereof, shall be designed and constructed to resist the wind loads determined in accordance with Chapters 26 through 31. The provisions of this chapter define basic wind parameters for use with other provisions contained in this standard.

26.1.2 Permitted Procedures. The design wind loads for buildings and other structures, including the MWFRS and C&C elements thereof, shall be determined using one of the procedures as specified in this section. An outline of the overall process for the determination of the wind loads, including section references, is provided in Fig. 26.1-1.

26.1.2.1 Main Wind Force Resisting System. Wind loads for the MWFRS shall be determined using one of the following procedures:

1. Directional Procedure for buildings of all heights as speci- fied in Chapter 27 for buildings meeting the requirements specified therein;

2. Envelope Procedure for low-rise buildings as specified in Chapter 28 for buildings meeting the requirements speci- fied therein;

3. Directional Procedure for Building Appurtenances (rooftop structures and rooftop equipment) and Other Structures (such as solid freestanding walls and solid freestanding signs, chimneys, tanks, open signs, single-plane open frames, and trussed towers) as specified in Chapter 29; or

4. Wind Tunnel Procedure for all buildings and all other structures as specified in Chapter 31.

26.1.2.2 Components and Cladding. Wind loads on C&C on all buildings and other structures shall be designed using one of the following procedures:

1. Analytical Procedures provided in Parts 1 through 6, as appropriate, of Chapter 30; or

2. Wind Tunnel Procedure as specified in Chapter 31.

26.2 DEFINITIONS

The following definitions apply to the provisions of Chapters 26 through 31:

APPROVED: Acceptable to the Authority Having Jurisdiction.

ATTACHED CANOPY: A horizontal (maximum slope of 2%) patio cover attached to the building wall at any height; it is different from an overhang, which is an extension of the roof surface.

BASIC WIND SPEED, V: Three-second gust speed at 33 ft (10 m) above the ground in Exposure C (see Section 26.7.3) as determined in accordance with Section 26.5.1.

BUILDING, ENCLOSED: A building that has the total area of openings in each wall, that receives positive external pressure, less than or equal to 4 sq ft (0.37 m2) or 1% of the area of that wall, whichever is smaller. This condition is expressed for each wall by the following equation:

Ao < 0.01Ag; or 4 sq ft ð0.37 m2Þ;whichever is smaller; where Ao and Ag are as defined for Open Buildings.

BUILDING, LOW-RISE: Enclosed or partially enclosed building that complies with the following conditions:

1. Mean roof height h less than or equal to 60 ft (18 m). 2. Mean roof height h does not exceed least horizontal

dimension.

BUILDING, OPEN: A building that has each wall at least 80% open. This condition is expressed for each wall by the equation Ao ≥ 0.8Ag, where

Ao = total area of openings in a wall that receives positive external pressure, in ft2 (m2); and

Ag = the gross area of that wall in which Ao is identified, in ft2

(m2).

BUILDING, PARTIALLY ENCLOSED: A building that complies with both of the following conditions:

1. The total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10%.

2. The total area of openings in a wall that receives positive external pressure exceeds 4 ft2 (0.37 m2) or 1% of the area of that wall, whichever is smaller, and the percentage of openings in the balance of the building envelope does not exceed 20%.

These conditions are expressed by the following equations:

Ao > 1.10Aoi

Ao > 4 ft2ð0.37 m2Þ or > 0.01Ag; whichever is smaller; andAoi∕Agi ≤ 0.20

where Ao and Ag are as defined for Open Building;

Aoi = sum of the areas of openings in the building envelope (walls and roof) not including Ao, in ft2 (m2); and

Agi = sum of the gross surface areas of the building envelope (walls and roof) not including Ag, in ft2 (m2).

Minimum Design Loads and Associated Criteria for Buildings and Other Structures 245

BUILDING, PARTIALLY OPEN: A building that does not comply with the requirements for open, partially enclosed, or enclosed buildings.

BUILDING, SIMPLE DIAPHRAGM: A building in which both windward and leeward wind loads are transmitted by roof and vertically spanning wall assemblies, through continuous floor and roof diaphragms, to the MWFRS.

BUILDING, TORSIONALLY REGULAR UNDER WIND LOAD: A building with the MWFRS about each princi- pal axis proportioned so that the maximum displacement at each story under Case 2, the torsional wind load case, of Fig. 27.3-8 does not exceed the maximum displacement at the same location under Case 1 of Fig. 27.3-8, the basic wind load case.

BUILDING ENVELOPE: Cladding, roofing, exterior walls, glazing, door assemblies, window assemblies, skylight assem- blies, and other components enclosing the building.