Live Load Reduction (ASCE 7 Ch. 4)

ASCE 7 §4.7 L = L0 (0.25 + 15/sqrt(KLL x AT)), where L0 is the unreduced live load, AT the tributary area, and KLL the element factor from Table 4.7-1 (interior/exterior columns 4, beams and cantilever-slab edge columns 2-3, other members 1). It applies only where KLL x AT >= 400 ft^2 and cannot drop below 0.50 L0 (one floor) or 0.40 L0 (two or more). A 50 psf office load on an interior column (KLL 4) with 400 ft^2 tributary reduces 37.5% to 31.25 psf; a 1,000 ft^2 area hits the 0.50 floor at 25 psf. Loads over 100 psf, garages, and assembly spaces are generally not reducible. A design aid; the adopted code and the engineer of record govern.

L = L0 (0.25 + 15/sqrt(KLL x AT)) where KLL x AT >= 400 ft^2; L >= 0.50 L0 (one floor) or 0.40 L0 (two or more); otherwise L = L0.

The ASCE 7 §4.7 reduction in uniform live loads, L = L0 (0.25 + 15/sqrt(KLL x AT)), with KLL from Table 4.7-1, by name; the equation is unchanged across ASCE 7-05 through 7-22.

ASCE 7 is available through the ASCE Library at ascelibrary.org; the §4.7 reduction equation and the Table 4.7-1 KLL factors are public.

Estimate. AHJ and licensed professional govern.

Field names used by the API: unreduced_load_psf, tributary_area_ft2, member_type, floors_supported, reduced_load_psf, kll_at_ft2

• Reduction equation L = L0 (0.25 + 15/sqrt(KLL x AT)), applied only where KLL x AT >= 400 ft^2ASCE 7 §4.7.2
• KLL factor the live-load element factor from Table 4.7-1 (1 to 4 by member type)ASCE 7 Table 4.7-1
• Floor limits L >= 0.50 L0 for one floor, 0.40 L0 for two or more floorsASCE 7 §4.7.2
• Non-reducible loads over 100 psf, garages, and assembly occupancies are generally not reducedASCE 7 §4.7.3-4.7.6