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RE: ASD biaxial bending allowable stress

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Title: RE: ASD biaxial bending allowable stress

>When calculating biaxial bending in
>beams, we generally use equation H1-3:
>fa/FA + fbx/Fbx + fby/Fby = 1.0
>which in many cases, allows us to
>use 0.66Fy as Fbx and 0.75Fy as Fby.
>However, we've recently reviewed calculations
>where Fbx and Fby are 0.60Fy,
>no matter what the compact length
>attributes of the beam are.
>Is the 0.6Fy in biaxial standard?

No. The ratios in the interaction check represent the percentage of the total member strength used up by each component of the load. The strengths (FA, Fbx and Fby, in this case) used in this check must each be calculated as though the member were subject only to that individual component of the total load. So the unbraced length will very much affect what column-only or beam-only equation must be used.