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1607.12 Reduction in Uniform Live Loads
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Except for uniform live loads at roofs, all other minimum uniformly distributed live loads, Lo, in Table 1607.1 are permitted to be reduced in accordance with Section 1607.12.1 or 1607.12.2. Uniform live loads at roofs are permitted to be reduced in accordance with Section 1607.14.2.
Subject to the limitations of Sections 1607.12.1.1 through 1607.12.1.3 and Table 1607.1, members for which a value of KLLAT is 400 square feet (37.16 m2) or more are permitted to be designed for a reduced uniformly distributed live load, L, in accordance with the following equation:
(Equation 16-7)
where:
Lo = Unreduced design live load per square foot (m2) of area supported by the member (see Table 1607.1).
KLL = Live load element factor (see Table 1607.12.1).
AT = Tributary area, in square feet (m2).
L shall be not less than 0.50Lo for members supporting one floor and L shall be not less than 0.40Lo for members supporting two or more floors.
LIVE LOAD ELEMENT FACTOR, KLL
| ELEMENT | KLL |
| 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 |
| Members not previously 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
|
Live loads that exceed 100 psf (4.79 kN/m2) shall not be reduced.
Exceptions:
- The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the live load shall be not less than L as calculated in Section 1607.12.1.
- 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.
The live loads shall not be reduced in passenger vehicle garages.
Exception: The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the live load be shall be not less than L as calculated in Section 1607.12.1.
As an alternative to Section 1607.12.1 and subject to the limitations of Table 1607.1, uniformly distributed 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.
- 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 not greater than 20 percent.Exception: 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 passenger vehicle parking garages except that the live loads for members supporting two or more floors are permitted to be reduced by not greater than 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 16-8
- For one-way slabs, the area, A, for use in Equation 16-8 shall not exceed the product of the slab span and a width normal to the span of 0.5 times the slab span.
(Equation 16-8)
For SI: R = 0.861(A — 13.94)
Such reduction shall not exceed the smallest of:
- 40 percent for members supporting one floor.
- 60 percent for members supporting two or more floors.
- R as determined by the following equation:
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