Steel LRFD spec question
Steel LRFD spec question
(OP)
My office is currently switching from ASD to LRFD and I am trying to familiarize myself with the LRFD spec. The question I have is regarding combined stresses and the P-delta effect. In the ASD spec the moment was magnified by a factor to account for this effect. From what I am reading of the LRFD spec, the moment is actually being reduced by 11%? Am I reading that correctly or am I missing something drastic. The combined stress equation (for Pu>0.2phiPn - which is the case where Pdelta must be considered), is Pu/(phiPn) + 8/9*(Mux/phiMnx + Muy/phiMny). At first, I thought this may have something to do with Cm, but then that would be applying a constant value to it instead of allowing you to specify Cm.






RE: Steel LRFD spec question
RE: Steel LRFD spec question
Multiply your moments by the appropriate B1 and B2 factors. if you look at B1 closely, you'll see a similarity to ASD.
RE: Steel LRFD spec question
Thanks for the clarification there. I assume then that the Mux and Muy in the interaction equation reflect the second order effects, i.e. that B1 and B2 must be used in computing them?
RE: Steel LRFD spec question
RE: Steel LRFD spec question
RE: Steel LRFD spec question