Subject: Re: Seismic Upgrade ..... Appeal to those who created the code
Date: Sat, 22 May 1999 11:52:17 EDT
In a message dated 5/21/99 11:47:35 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 veirtical 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 do not think that the last sentence is correct. The damage referred to was
due to the <lack> of steel moment frame in tuck-under parking type apartment
buildings. It was common in those days to design apartment or condo buildings
with tuck-under parking where the open side had only steel columns supporting
wood or steel beams, and the rear wall of the parking space was assumed to
resist the diaphragm shear by the "Rotation Principle." I personally observed
a number of these buildings, and am sure many others have as well.
Oshin Tosounian, S.E.