Need a book? Engineering books recommendations...
RE: wind pressures[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: RE: wind pressures
- From: "Casey K. Hemmatyar" <khemmatyar(--nospam--at)gmail.com>
- Date: Mon, 24 Aug 2009 10:21:10 -0700
Sent: Thursday, August 20, 2009 6:15 PM
Subject: RE: wind pressures
This general increase for the entire southern half of Los Angeles County appears to have been from an incorrect reading of the ASCE 7-05 wind diagram, Fig. 6-1, which shows that area as a Special Wind Region. That figure shows all of CA, OR and WA to be in the 85 mph rather than a 100 mph zone. Whereas the special wind regions are those where the engineer should check for areas where designated special topographic features require the use of higher values; an example being L.A. City Document No. P/BC 2008-016.
Both ASCE 7 and the UBC have had identical wind maps since the early '80's and the UBC had similar maps since 1961. Therefore, the basic wind speed in this area is 85 mph and higher speeds are called for only where terrain features and established local records indicate higher wind speeds exist. I do not think that such features and records exist in the flat areas of the Los Angeles basin where the new ordinance applies and it is pretty unreasonable to expect the builder of a residence or a small commercial or industrial building to pay for a specific wind study by a meteorologist to justify what is in ASCE 7 and what has worked well in the past. All that will do is add significant cost increases to every modest structure that is built.
What is needed is a compilation of areas with special topographic features such as mouths of canyons or mountain tops where very high winds have been recorded so that the public can be informed and not exposed to unnecessary and costly restrictions.
Richard Hess, S.E.
LA County has adopted 100 mph wind special region area ordinance.
Khashayar "Casey" Hemmatyar, SE
Private email <khemmatyar(at)hotmail.com>
This doesn't seem too large to me. In Los Angeles where we have never had a hurricane, we desing for 20 psf usually, so 38 psf doesn't seem too large.
Stan Scholl, P.E.
خشایار (فریبرز) همت یار
- Prev by Subject: RE: wind pressures
- Next by Subject: Wood building withstands major-earthquake shake test
- Previous by thread: RE: wind pressures
- Next by thread: re: being the prime/ Stan