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Wood Lateral Distribution Factor for a load directly over a beam?

Wood Lateral Distribution Factor for a load directly over a beam?

Wood Lateral Distribution Factor for a load directly over a beam?

(OP)
A concentrated load is placed on 2”x6” decking (wide face bearing) over a 2”x8” joist. If the load is centered on the joist, can the NDS lateral distribution factor be applied? Generally I would conservatively assume that 100% of the load applies directly to the beam but in this case we need to find load reductions anywhere we can. The NDS commentary (C15.1.1) states “Generally all designs involving multiple parallel bending members that are loading through traverse elements such as flooring, decking, or sheathing are capable of some lateral distribution of a concentrated load on one member to adjacent members on either side. The repetitive member factor (see NDS 4.3.9, 7.3.6, 8.3.7) partially accounts for such load redistribution.”

RE: Wood Lateral Distribution Factor for a load directly over a beam?

No I don't think so. They don't have any distribution factors analogous to the live load distribution factors for girders under AASHTO that I'm aware of. Your stuck with the repetitive factor giving you an "increased" capacity on your joist, unless you could justify otherwise with nonlinear FEA.

RE: Wood Lateral Distribution Factor for a load directly over a beam?

If your point load occurs in a specific location along the joist span, you could run a quick stiffness analogy check. I've done this a few times in the past with bridge decks -- model the deck element spanning across the appropriate number of spring supports (calculated for the joist's bending stiffness at the point of load application) to see exactly how much would shed to adjacent joists.

Typically it isn't much though, and I wouldn't use that in conjunction with the NDS repetitive factor.

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