### International Building Code 1605.1

General. Buildings and other structures and portions

thereof shall be designed to resist the load combinations specified

in Section 1605.2 or 1605.3 and Chapters 18 through 23,

and the special seismic load combinations of Section 1605.4

where required by Section 12.3.3.3 or 12.10.2.1 of ASCE 7.

Applicable loads shall be considered, including both earthquake

and wind, in accordance with the specified load combinations.

Each load combination shall also be investigated with

one or more of the variable loads set to zero.

### International Building Code 1605.2

Load combinations using strength design or load

and resistance factor design.

Basic load combinations. Where strength design

or load and resistance factor design is used, structures and

portions thereof shall resist the most critical effects from the

following combinations of factored loads:

1.4 (D+F) (Equation 16-1)

1.2(D + F + T) + 1.6(L + H) +

0.5 (Lr or S or R) (Equation 16-2)

1.2D+ 1.6(Lr or S or R) + (f1L or 0.8W) (Equation 16-3)

1.2D+ 1.6W+ f1L + 0.5(Lr or S or R) (Equation 16-4)

1.2D+ 1.0E+ f1L + f2S (Equation 16-5)

0.9D+ 1.6W+ 1.6H (Equation 16-6)

0.9D+ 1.0E+ 1.6H (Equation 16-7)

f1 = 1 for floors in places of public assembly, for live loads

in excess of 100 pounds per square foot (4.79 kN/m2),

and for parking garage live load, and

= 0.5 for other live loads.

f2 = 0.7 for roof configurations (such as saw tooth) that do

not shed snow off the structure, and

= 0.2 for other roof configurations.

Exception: Where other factored load combinations are

specifically required by the provisions of this code, such

combinations shall take precedence.

Other loads. Where Fa is to be considered in the

design, the load combinations of Section 2.3.3 of ASCE 7

shall be used.

### International Building Code 1605.2.1

Basic load combinations. Where strength design

or load and resistance factor design is used, structures and

portions thereof shall resist the most critical effects from the

following combinations of factored loads:

1.4 (D+F) (Equation 16-1)

1.2(D + F + T) + 1.6(L + H) +

0.5 (Lr or S or R) (Equation 16-2)

1.2D+ 1.6(Lr or S or R) + (f1L or 0.8W) (Equation 16-3)

1.2D+ 1.6W+ f1L + 0.5(Lr or S or R) (Equation 16-4)

1.2D+ 1.0E+ f1L + f2S (Equation 16-5)

0.9D+ 1.6W+ 1.6H (Equation 16-6)

0.9D+ 1.0E+ 1.6H (Equation 16-7)

f1 = 1 for floors in places of public assembly, for live loads

in excess of 100 pounds per square foot (4.79 kN/m2),

and for parking garage live load, and

= 0.5 for other live loads.

f2 = 0.7 for roof configurations (such as saw tooth) that do

not shed snow off the structure, and

= 0.2 for other roof configurations.

Exception: Where other factored load combinations are

specifically required by the provisions of this code, such

combinations shall take precedence.

### International Building Code 1605.2.2

Other loads. Where Fa is to be considered in the

design, the load combinations of Section 2.3.3 of ASCE 7

shall be used.

### International Building Code 1605.3

Load combinations using allowable stress design.

Basic load combinations. Where allowable stress

design (working stress design), as permitted by this code, is

used, structures and portions thereof shall resist the most

critical effects resulting from the following combinations of

loads:

D+F (Equation 16-8)

D+H+F+ L + T (Equation 16-9)

D+H+F+ (Lr or S or R) (Equation 16-10)

D + H + F + 0.75(L + T) +

0.75 (Lr or S or R) (Equation 16-11)

D+H+F+ (Wor 0.7E) (Equation 16-12)

D + H + F + 0.75(W or 0.7E) +

0.75L + 0.75 (Lr or S or R) (Equation 16-13)

0.6D+W+H (Equation 16-14)

0.6D+ 0.7E+H (Equation 16-15)

Exceptions:

1. Crane hook loads need not be combined with roof

live load or with more than three-fourths of the

snow load or one-half of the wind load.

2. Flat roof snow loads of 30 psf (1.44 kN/m2) or less

need not be combined with seismic loads. Where

282 2006 INTERNATIONAL BUILDING CODE

STRUCTURAL DESIGN

flat roof snow loads exceed 30 psf (1.44 kN/m2),

20 percent shall be combined with seismic loads.

Stress increases. Increases in allowable

stresses specified in the appropriate material chapter or

the referenced standards shall not be used with the load

combinations of Section 1605.3.1, except that a duration

of load increase shall be permitted in accordance with

Chapter 23.

Other loads. Where Fa is to be considered in

design, the load combinations of Section 2.4.2 of ASCE

7 shall be used.

Alternative basic load combinations. In lieu of the

basic load combinations specified in Section 1605.3.1, structures

and portions thereof shall be permitted to be designed for

the most critical effects resulting from the following combinations.

When using these alternative basic 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 wind loads are calculated in accordance

with Chapter 6 of ASCE 7, the coefficient ? in the following

equations shall be taken as 1.3. For other wind loads, ? shall be

taken as 1. When 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. When 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.

D+ L + (Lr or S or R) (Equation 16-16)

D+ L + (?W) (Equation 16-17)

D+ L +?W+ S/2 (Equation 16-18)

D+ L + S +?W/2 (Equation 16-19)

D+ L + S +E/1.4 (Equation 16-20)

0.9D+E/1.4 (Equation 16-21)

Exceptions:

1. Crane hook loads need not be combined with roof live

loads or with more than three-fourths of the snow load

or one-half of the wind load.

2. Flat roof snow loads of 30 psf (1.44 kN/m2) or less

need not be combined with seismic loads. Where flat

roof snow loads exceed 30 psf (1.44 kN/m2), 20 percent

shall be combined with seismic loads.

Other loads. Where F, H or T are to be considered

in the design, each applicable load shall be added

to the combinations specified in Section 1605.3.2.

### International Building Code 1605.3.1

Basic load combinations. Where allowable stress

design (working stress design), as permitted by this code, is

used, structures and portions thereof shall resist the most

critical effects resulting from the following combinations of

loads:

D+F (Equation 16-8)

D+H+F+ L + T (Equation 16-9)

D+H+F+ (Lr or S or R) (Equation 16-10)

D + H + F + 0.75(L + T) +

0.75 (Lr or S or R) (Equation 16-11)

D+H+F+ (Wor 0.7E) (Equation 16-12)

D + H + F + 0.75(W or 0.7E) +

0.75L + 0.75 (Lr or S or R) (Equation 16-13)

0.6D+W+H (Equation 16-14)

0.6D+ 0.7E+H (Equation 16-15)

Exceptions:

1. Crane hook loads need not be combined with roof

live load or with more than three-fourths of the

snow load or one-half of the wind load.

2. Flat roof snow loads of 30 psf (1.44 kN/m2) or less

need not be combined with seismic loads. Where

282 2006 INTERNATIONAL BUILDING CODE

STRUCTURAL DESIGN

flat roof snow loads exceed 30 psf (1.44 kN/m2),

20 percent shall be combined with seismic loads.

Stress increases. Increases in allowable

stresses specified in the appropriate material chapter or

the referenced standards shall not be used with the load

combinations of Section 1605.3.1, except that a duration

of load increase shall be permitted in accordance with

Chapter 23.

Other loads. Where Fa is to be considered in

design, the load combinations of Section 2.4.2 of ASCE

7 shall be used.

### International Building Code 1605.3.1.1

Stress increases. Increases in allowable

stresses specified in the appropriate material chapter or

the referenced standards shall not be used with the load

combinations of Section 1605.3.1, except that a duration

of load increase shall be permitted in accordance with

Chapter 23.

### International Building Code 1605.3.1.2

Other loads. Where Fa is to be considered in

design, the load combinations of Section 2.4.2 of ASCE

7 shall be used.

### International Building Code 1605.3.2

Alternative basic load combinations. In lieu of the

basic load combinations specified in Section 1605.3.1, structures

and portions thereof shall be permitted to be designed for

the most critical effects resulting from the following combinations.

When using these alternative basic 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 wind loads are calculated in accordance

with Chapter 6 of ASCE 7, the coefficient ? in the following

equations shall be taken as 1.3. For other wind loads, ? shall be

taken as 1. When 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. When 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.

D+ L + (Lr or S or R) (Equation 16-16)

D+ L + (?W) (Equation 16-17)

D+ L +?W+ S/2 (Equation 16-18)

D+ L + S +?W/2 (Equation 16-19)

D+ L + S +E/1.4 (Equation 16-20)

0.9D+E/1.4 (Equation 16-21)

Exceptions:

1. Crane hook loads need not be combined with roof live

loads or with more than three-fourths of the snow load

or one-half of the wind load.

2. Flat roof snow loads of 30 psf (1.44 kN/m2) or less

need not be combined with seismic loads. Where flat

roof snow loads exceed 30 psf (1.44 kN/m2), 20 percent

shall be combined with seismic loads.

Other loads. Where F, H or T are to be considered

in the design, each applicable load shall be added

to the combinations specified in Section 1605.3.2.

### International Building Code 1605.3.2.1

Other loads. Where F, H or T are to be considered

in the design, each applicable load shall be added

to the combinations specified in Section 1605.3.2.

### International Building Code 1605.4

Special seismic load combinations. For both allowable

stress design and strength design methods where specifically

required by Section 1605.1 or by Chapters 18 through 23,

elements and components shall be designed to resist the forces

calculated using Equation 16-22 when the effects of the seismic

ground motion are additive to gravity forces and those calculated

using Equation 16-23 when the effects of the seismic

ground motion counteract gravity forces.

1.2D+ f1L +Em (Equation 16-22)

0.9D+Em (Equation 16-23)

where:

Em = The maximum effect of horizontal and vertical forces

as set forth in Section 12.4.3 of ASCE 7.

f1 = 1 for floors in places of public assembly, for live loads

in excess of 100 psf (4.79 kN/m2) and for parking

garage live load, or

= 0.5 for other live loads.

### International Building Code 1605.5

Heliports and helistops. Heliport and helistop landing

areas shall be designed for the following loads, combined in

accordance with Section 1605:

1. Dead load, D, plus the gross weight of the helicopter, Dh,

plus snow load, S.

2. Dead load,D, plus two single concentrated impact loads,

L, approximately 8 feet (2438 mm) apart applied anywhere

on the landing area (representing the helicopter’s

two main landing gear, whether skid type or wheeled

type), having a magnitude of 0.75 times the gross weight

of the helicopter. Both loads acting together total

one-and one half times the gross weight of the helicopter.

3. Dead load,D, plus a uniform live load, L, of 100 psf (4.79

kN/m2).

Exception: Landing areas designed for helicopters

with gross weights not exceeding 3,000 pounds

(13.34 kN) in accordance with Items 1 and 2 shall be

permitted to be designed using a 40 psf (1.92 kN/m2)

uniform live load in Item 3, provided the landing area

is identified with a 3,000 pound (13.34 kN) weight

limitation. This 40 psf (1.92 kN/m2) uniform live load

shall not be reduced. 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 landing

area weight limitation shall be a minimum of 5

feet (1524 mm) in height.