To: SEAOC List Server <seaint(--nospam--at)seaint.org>
Subject: Design Lateral Force, Fp, Per 1997 UBC
From: John Lawson <jlawson(--nospam--at)kramerinc.com>
Date: Tue, 11 May 1999 22:34:09 -0700
1997 UBC Section 1630.1.1 which states E=pEh + Ev will have to have
0.5CaID applied to your masonry wall (and tilt-up walls), but not in the
out-of-plane direction. Here's how it's done....
The horizontal Fp force acting on the wall out-of-plane is calculated
and designated as Eh. Acting at the same time on these "slender walls"
is a P-delta moment as required in the alternative slender wall design
sections for concrete or masonry. This P-delta moment is influenced by
the wall's self dead weight and roof (and floors) weight during
The load combination applicable is equation 12-5 which uses a 1.2 load
factor on D. Ev is to be added to this 1.2. Ev is approximately 0.20
where Ca is 0.40, and thus the 1.2 load factor becomes 1.4 which is the
same as under previous codes.
John Lawson SE
Kramer & Lawson, Inc.