I attended an ICBO seminar in June 98' on the 1997 UBC Earthquake
Regulations. At the seminar, the speaker indicated that Eqn. 30-7 should
also be included with Eqn. 30-6 in the section you speak of. I'll leave it
up to others to try and answer your question as to why.
From: Gerard Madden [mailto:GMadden(--nospam--at)mplusl.com]
Sent: Friday, February 02, 2001 12:50 PM
Subject: Drift per 1997 UBC
Does anyone know why the drift check requires you to use the minimum base
shear for buildings in Zone 4? What I'm talking about is UBC 1630.10.3
Limitations where it states that the limitations of equation (30-6) may be
disregarded when checking drift. No mention is made of equation (30-7) which
is the zone 4 minumum. There was no distinction in the 1994UBC based on
This can greatly impact design for buildings with periods greater than 3
seconds in zone 4.
Any comments are appreciated.
Gerard Madden, P.E.
Middlebrook + Louie, Structural Engineers
71 Stevenson Street, Suite 2100
San Francisco, CA 94105