I-Joists and Deflection
To the Editor:
I read with interest John
Siegenthaler's article "Wood I-Joist
Fundamentals" (Practical Engineering,
10/95). I am curious why the author
did not mention deflection in this article,
as this often controls in bending
member design.
John "Buddy" Showalter, P.E.
American Wood Council
Washington, D.C.
John Siegenthaler responds:
The purpose of the article was to
illustrate to builders (who are often
more familiar with hefty solid-sawn
lumber) how an I-joist, with its thin
profile and light weight, can handle the
bending forces present in a floor joist.
Nevertheless, your point is a good one;
namely, that deflection — of either a
solid-sawn joist or an I-joist — is usually
the limiting factor in joist selection.
Most building codes allow