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Re: Period Calculation for One Story Building with Flexible Diaphragm, FEMA 3

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Bruce Resnick,

Thank you for your comments.  I did not make it clear that the FEMA 310,
Equation (4-1) applied to FEMA 310 and not to the !994 Uniform Building Code.
FEMA 310 is an evaluation document used to seismic evaluate an existing
building, not design a new building.  In FEMA 310, one needs to calculate as
accurate a fundamental period of vibration, T, as possible - short of a full
blown dynamic analysis - in order to obtain the "Pseudo Lateral Force" base
shear for the existing building, because FEMA 310 attempts to use the "real"
seismic forces on an existing building, not "code" seismic forces that are
reduced by Rw for the UBC or R for 1994 NEHRP.

FEMA 310 presents the Equation (4-1) to calculate the period, T, of a one
story building with a single span flexible diaphragm with the anticipation
that the period, T, will be much larger than the period, T, calculated using
the 1994 UBC and 1994 NEHRP equations to calculate the period, T.  With this
longer period, T, the FEMA 310 "Pseudo Lateral Force" - the "Base Shear" -
would be reduced.

If you do not have a copy of FEMA 310,  you should get a copy by calling the
FEMA Distribution Facility at 1-800-480-2520.

I would be very interested in your comments concerning how you would calculate
the fundamental period of vibration, T, for a one story building with a single
span flexible diaphragm, other than using the 1994 UBC and 1994 NEHRP default
equations.
Does the FEMA 310, Equation (4-1) look reasonable to you? Please refer to my
previous email message to the SEAOC List Server on this subject.

Frank E. McClure    FEMCCLURE(--nospam--at)aol.com