Try checking your frame model and make sure that all columns supporting the beams which are failing have the correct support condition (fixed or pinned). I had a similar problem when I forgot to put a support condition to column below a beam.
From: bill@polhemus.cc [mailto:bill@polhemus.cc]
Sent: Thursday, April 16, 2009 1:57 PM
To:
Subject: RISA-3D Steel WF Torsion
I'm getting some anomalous results from a rather complicated steel frame run on RISA-3D. I'm doing RSA with this, and I have already noticed some peculiar results (at least for this "statics-based" puke).
When I look at the "Shear Check" plot on-screen, I'll see a lot of failures of wide-flange members (mostly beams), many with rather large "understrength factors" (if you will; I guess we used to say "overstress"), between 3.0 and 4.0.
But when I look at the specifics of a given member, I don't see any large shears at all. I'm inclined to think it might be a torsion problem showing up, but even the torsion doesn't seem that great (although it is present).
Any thoughts?