That sounds like a typical plywood box beam. I'm checking AITC and the old UBC - I recall these were covered therein. I used to design a lot of these but that was back when I could remember. I'll keep looking.
Bob Garner, S.E.
From: Bill Allen [mailto:t.w.allen@cox.net]
Sent: Thursday, January 15, 2009 10:51 AM
To:
Subject: Lateral Stability of a Box Beam ?
I have a situation requiring two beams, approximately 12" apart spanning about 27 feet. They aren't supporting much more than their own weight, but I'm concerned that if I just use the span as the unbraced length, the beams are going to be very large.
I would like to put plywood top and bottom to increase the effective lateral torsional strength. Is there a good reference in determining the capacity of such an assembly in wood?
Thank you,
T. William (Bill) Allen, S.E.
Consulting Structural Engineers
V (949) 248-8588 •