1607.9 Reduction in Live Loads
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:
L = Reduced design live load per square foot (square meter) of area supported by the member.
Lo = Unreduced design live load per square foot (square 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.
|Exterior columns without cantilever slabs||4|
|Edge columns with cantilever slabs||3|
|Corner columns with cantilever slabs||2|
|Edge beams without cantilever slabs||2|
|All other members not identified above including:
- 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.
- 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.
- A reduction shall not be permitted in Group A occupancies.
- 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.
- 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.
- 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 Equation 16-23.
- For one-way slabs, the area, A, for use in Equation 16-23 shall not exceed the product of the slab span and a width normal to the span of 0.5 times the slab span.
R = 0.08(A - 150) (Equation 16-23)
For SI: R = 0.861(A - 13.94)
Such reduction shall not exceed the smallest of:
- 40 percent for horizontal members;
- 60 percent for vertical members; or
- R as determined by the following equation.
R = 23.1(1 + D/Lo) (Equation 16-24)
A = Area of floor supported by the member, square feet (m2).
D = Dead load per square foot (m2) of area supported.
Lo = Unreduced live load per square foot (m2) of area supported.
R = Reduction in percent.