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Re: FEMA 310 - Handbook for the Seismic Evaluation of Buildings - A Prestandard.
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- Subject: Re: FEMA 310 - Handbook for the Seismic Evaluation of Buildings - A Prestandard.
- From: Lynn <lhoward(--nospam--at)silcom.com>
- Date: Thu, 22 Oct 1998 10:08:45 -0700
Frank- Obviously something is wrong here. Before the "prestandard" is made a "standard" further review should be made to weed out some of these problems. We have used FEMA 310 in the recent past as a guideline for evaluation of structures. Using engineering judgment along with the guidelines is very important. There are other issues, particularly with wood framed structures, that appear to be overly conservative for life-safety level of performance. Lynn FEMCCLURE(--nospam--at)aol.com wrote: > > At the 1998 SEAOC Convention in Sparks, Nevada, there was a paper concerning > FEMA 310, which presented a strength comparison between the provisions of FEMA > 178 and FEMA 310, but did not consider the problems related to global > overturning using FEMA 310. Call FEMA at 1-800-480-2520 for your free copy of > FEMA 310. > > The following discussion is based on my structural calculations, which I made > on the "back of an envelope" using my 6" slide rule, and represents the > results of the application of the overturning provisions in FEMA 310 to a > sample building. > > Consider a 30 foot high, three story reinforced concrete "Bearing Wall" > building with reinforced concrete shear walls. The building is three bays > wide ( three times 25 ft. = 75 ft.) by four bays long (four times 30 ft = 120 > ft.) > > The average building weight is 175 lbs. per sq. ft. and the total building > weight is 4,735 kips. The fundamental period is 0.26 sec. The "Pseudo > Lateral Force" (Base Shear) is 6,284 kips, which is 133% gravity times the > total building weight, according to FEMA 310, (Equation 3-1) > > To conform to the requirements of FEMA 310, the building requires a reinforced > concrete shear wall at each end of the building, which is 36" thick by 25 ft. > long by 30 ft. high. Taking into account 90% of the resisting dead load > tributary to a single reinforced concrete shear wall , FEMA 310 provisions at > the Foundation Soil Interface (Section 4.2.4.3.4, FEMA 310) requires an > equivalent of a tension hold-down force equal to 472 kips and a compressive > force of 1,203 kips concentrated at the reinforced columns at the ends of the > single reinforced concrete shear wall at each end of the building. > > Does a 36" thick by 25 foot long reinforced concrete shear wall look > reasonable at each end of a 75 ft. x 120 ft. three story reinforced concrete > building? > > Do the tensile hold-down force of 472 kips and a compressive force of 1,203 > kips at the ends of the reinforced concrete shear wall look reasonable? > > Are you aware of any similar building designed and constructed in California > in Seismic Zone or 4, according to the 1994 Uniform Building Code, that would > not be a candidate for a major seismic rehabilitation or retrofit if FEMA 310 > criteria was used for the seismic evaluation and rehabilitation or retrofit? > > I would appreciate any similar examples concerning the application of the > overturning provisions of FEMA 310 and/or FEMA 273. > > Frank E. McClure FEMCCLURE(--nospam--at)aol.com October 22, 1998
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