Subject: RE: 14 story concrete shear wall building retrofit -- 1997 Unifor
From: David B Merrick <mrkgp(--nospam--at)pacbell.net>
Date: Wed, 29 Aug 2001 10:49:48 -0700
I have confirmed that the Abatement of Dangerous Buildings' (UCADB) was not
updated to reflect the 1997 UBC. It seems that many existing buildings, or most,
may now be deemed dangerous per UCADB. The UCADB needs to be updated.
Areas most affected include
Omega force factor for irregularities.
Rho force factor for the lack of redundancy.
Minimum sill bolts diameters in wood design
Rigid diaphragm force requirements in wood design
Years ago an expert claimed that there is a difference between the terms load and
force. "Force" being related to lateral forces and "loads" being used for vertical
loads. He thought that the UCADB should not be applied to wind and seismic
designs. I believe it is not that clear.
The term imminent is used. Most structurally dangerous conditions need an "event"
to trigger the collapse. A qualifying "event" might be limited to a loading that
is allowed by the code. A code complying earthquake force would then be imminent.
When a working allowed load causes a 1.5 over stress, yield will then
theoretically occur when the maximum allowed load is applied. Some lateral force
code adjustments may be conservative and may not as accurately be used to predict
a yielding (in working stress designs). Some code adjustments when failed by the
66% rule, may not be as imminent of a hazard as the UCADB has intendended. (if one
can measure imminent).
Other issues may be dangerous prior to being less than 0.66 of code. Such as the
conventional construction rules for wood framing. UMB regulations.
Architectural, electrical and mechanical issues need to be reviewed in addition to
* This email was sent to you via Structural Engineers
* Association of Southern California (SEAOSC) server. To
* subscribe (no fee) or UnSubscribe, please go to:
* Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
* send to the list is public domain and may be re-posted
* without your permission. Make sure you visit our web
* site at: http://www.seaint.org