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Re: FEMA 310 - Handbook for the Seismic Evaluation of Buildings - A Prestandard.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: FEMA 310 - Handbook for the Seismic Evaluation of Buildings - A Prestandard.
- From: Eddie Gonzalez <Eagonzal(--nospam--at)ENG.CI.LA.CA.US>
- Date: Thu, 22 Oct 1998 10:57:30 -0700
Frank, can you please answer the following questions about your calculations: Q1: Can you please elaborate on what you mean by, "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." Can you list the Section that led to this size of wall? I am assuming that you did not use the load you calculated as a direct input for the wall length and thickness but instead applied the approriate "m" factors, particularly since equ. 3-1 is so that inelastic displacements can be mimiced. Q2: Since you refer to Sections in Chapter 4, I am assuming you are doing a TIER 2 Evaluation. Therefore, since its a force-controlled action, per Section 188.8.131.52.2, it the load you are listing one you obtained from Method 1 (Quf = Qg + Max. force that can be delivered) or Method 2 [Quf = Qg +/- Qe/(CJ) ; Quf = Qg +/- Qe/C]? Regards, ed gonzalez >>> <FEMCCLURE(--nospam--at)aol.com> 10/22/98 12:54AM >>> 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 184.108.40.206.4, 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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