1607.9.1
General. Subject to the limitations of Sections 1607.9.1.1
through 1607.9.1.4, members for which a value of KLLAT
is 400 square feet (37.16 m2) or more are permitted
to be designed for a reduced live load in accordance with
the following equation:
(Equation 16-24)
where:
L
= Reduced design live load per square foot (meter) of area
supported by the member.
La
= Unreduced design live load per square foot (meter) of
area supported by the member (see Table
1607.1).
KLL= Live load element
factor (see Table 1607.9.1).
AT
= Tributary area, in square feet (square meters). 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.
1607.9.1.1 Heavy live loads. Live loads that exceed
100 psf (4.79 kN/m2) shall not be reduced.
Exceptions:
1. The
live loads for members supporting two or more floors
are permitted to be reduced by a maximum of 20 percent,
but the live load shall not be less than L as calculated
in Section 1607.9.1.
2. For
uses other than storage, where approved, additional
live load reductions shall be permitted where shown
by the registered design professional that a rational
approach has been used and that such reductions are
warranted.
1607.9.1.2
Passenger vehicle garages. The live loads shall not
be reduced in passenger vehicle garages except the live
loads for members supporting two or more floors are permitted
to be reduced by a maximum of 20 percent, but the live
load shall not be less than L as calculated in Section
1607.9.1.
1607.9.1.3 Special occupancies. Live loads of 100
psf (4.79 kN/m2) or less shall not be reduced
in public assembly occupancies.
1607.9.1.4 Special structural elements. Live loads
shall not be reduced for one-way slabs except as permitted
in Section 1607.9.1.1. Live loads of 100 psf (4.79 kN/m2)
or less shall not be reduced for roof members except as
specified in Section 1607.11.2.
1607.9.2 Alternate floor live load reduction. As an
alternative to Section 1607.9.1, floor 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.
1. A reduction shall not be permitted in Group A
occupancies.
2. A reduction shall not be permitted where the live
load exceeds 100 psf (4.79 kN/m2) except that
the design live load for members supporting two or more
floors is permitted to be reduced by 20 percent.
3. A reduction shall not be permitted in passenger
vehicle parking garages except that the live loads for
members supporting two or more floors are permitted to
be reduced by a maximum of 20 percent.
4. For live loads not exceeding 100 psf (4.79 kN/m2),
the design live load for any structural member supporting
150 square feet (13.94 m2) or more is permitted
to be reduced in accordance with the following equation:
R = 0.08 (A -150)
(Equation 16-25)
For SI: R =
0.861 (A -13.94)
Such reduction shall not
exceed the smallest of:
1. 40 percent
for horizontal members;
2. 60 percent
for vertical members; or
3. R as determined
by the following equation.
R = 23.1 (1 + D/Lo)
(Equation 16-26)
where:
A = Area of
floor supported by the member, square feet (m2),
D = Dead load per
square foot (m2) of area supported.
La =
Unreduced live load per square foot (m2)
of area supported.
R =
Reduction in percent.
