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Re: FEMA 310 - Handbook for the Seismic Evaluation of Buildings - A Prestandard.

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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
4.2.4.3.2, 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 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