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RE: RISA-3D Steel WF Torsion

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Bill,
Wide flange shapes have a very low capacity in torsion.  The other issue with torsion is the end connections.  If the local member is not torsionally restrained at the support, there is no resistance, but that normally will give you an instability.  I would still be suspicious of a problem with the member end contraints / releases. 

Regards, Harold Sprague

 
> From: bill(--nospam--at)polhemus.cc [mailto:bill(--nospam--at)polhemus.cc]
> Sent: Thursday, April 16, 2009 1:57 PM
> To: seaint(--nospam--at)seaint.org
> 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?
>



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