International Building Code Section 1605


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.