From: Jim Kestner <jkestner(--nospam--at)somervilleinc.com>
Date: Tue, 06 Apr 1999 07:38:30 -0500
This is purely a matter of relative stiffnesses. The shear walls and
the metal deck diaphragm should be stiff enough to prevent the column
from achieving translation sufficient enough to cause buckling. Does he
agree with this? If not, you may have to do some calculations to prove
this to him. You might even suggest referencing Dr. Yura's papers.
Perhaps this person's only argument might be with the detail at the top
of the column (although I know that it is commonly used). A minor change
might satisfy this person and get you out of a no win situation. I would
suggest positively bracing the bottom of the girder (or the top of the
column) with a joist bottom chord extension or an angle brace down from
the nearest joist top chord panel point. Personally, I do not like the
girder (with a stiffener) sitting on top of the column without a
positive brace point at or near the bottom of the girder (or top of the
With your detail, is the bottom of the beam bracing the top of the
column or is the top of the column bracing the bottom of the beam? Or
should it be assumed that the column runs completely thru to the top of
the girder and therefore the column is braced by the top of the girder
and the bottom of the girder is braced by the column? What happens to
this unbraced point during a earthquake? How much lateral force would it
take to push it out? Have you seen what happens to that point when a
fork truck hits the bottom of the column?
Jim Kestner, P.E.
Green Bay, Wi.