Return to index: [Subject] [Thread] [Date] [Author]

ASD vs LRFD...my simple test

[Subject Prev][Subject Next][Thread Prev][Thread Next]
My intent here is not to raise anybody's blood pressure.  However,
yesterday I had a couple of minutes and thought I'd try a quick
comparison between ASD and LRFD.  I have a large 2-story structure
(210'x270').  Bay sizes are 21'x27', 10 each direction.  I optimized a
typical bay of roof framing using ASD, and then tried LRFD.  Know what?
I got the exact same member sizes!  I guess that might not be a surprise
to some of you, but it was to me.  

The whole thing took me a little longer than ASD (not that its hard or
difficult, just different).  It didn't feel right and I certainly didn't
save any money for the client.

Question:  When is it that LRFD would produce smaller beam sizes?  Maybe
I'll try the same test on the 2nd floor framing, since I have much
higher live loads than on the roof.  I'll report my findings if they
favor LRFD.

Michael Ritter, PE