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Vertical Force Distribution - UBC97
- To: <seaint(--nospam--at)seaint.org>
- Subject: Vertical Force Distribution - UBC97
- From: "YI" <YI(--nospam--at)summit-sr.com>
- Date: Mon, 17 May 2004 16:23:04 -0700
seismic force vertically, basically using the ratio of floor weight times the
height. Consider a three story building, if the roof is a plywood
diaphragm, and the floors below are all concrete deck, e.g. rigid
diaphragm. Would the vertical force distribution still occur as described
in UBC97, 1630.5? That is, does the lateral force in the roof diaphragm
need to be calculated according to section 1630.5 of UBC97, which mostly like
means a higher force than the base shear calculated at the roof
SEAONC bluebook says
that when the structure deformation differs significantly from the assumed liner
mode behavior, in this case the roof diaphragm will deform a lot more than the
concrete diaphragm below, consideration should be given to alternate methods of
distributing the forces sucha s dynamic analysis.
Is there any other
method you use in this situation, to avoid doing a dynamic analysis? Do
you just ignor the vertically distributed force in UBC97, and use just the base
shear at the roof level as the design force?
Y i Y a n g,
SUMMIT ENGINEERING INC.
Santa Rosa, California