Subject: Re: Seismic Upgrade ..... Appeal to those who created the code
Date: Sun, 23 May 1999 23:38:02 EDT
In a message dated 5/21/99 11:47:45 PM Pacific Daylight Time, Sadre(--nospam--at)AOL.COM
PARAGRAPH # 4):
It is important to consider the relative stiffness of wood shear walls and
other vertical elements of the lateral force resisting system. An example
would be steel moment frames used in combination with wood shear walls. If
the steel frames are quite flexible, the shear walls are likely to carry a
large portion of the story shear than would be suggested by a tributary area
analysis. The relative flexibiltiy of steel moment frame may have
contributed to damage to tuck-under parking (soft story) buildings during
1994 Northridge earthquake [Mendes, 1995].
I can't disagree with this last sentence more!! Most tuck under parking
(soft story condition) did not have steel moment frames. Usually 3-1/2"
diameter pipe columns or wood posts were used to support usually wood beams.
These beams & columns were adequate to support gravity loads, however
lateral loads were designed to be resisted by rotation. Strangely enough,
numerous structures of this type suffered no noticeable damage, although
quite a few structures were distressed and damaged
Andrew Vidikan P.E.