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ATC Technical Seminar Series on FEMA 273 Guidelines

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Applied Technology Council (www.atcouncil.org) has announced a technical
seminar series on FEMA 273 "Guidelines for the Seismic Rehabilitation of
Buildings" starting in San Diego, CA on November 5-6, 1998, followed by Salt
Lake City, Utah on November 19 - 20, 1998. and Portland, Oregon on December
8-9,1998.  These FEMA 273 seminars will also be held at other cities like Los
Angeles, CA, Charleston, South Carolina, New York, New York, St. Louis,
Missouri, San Francisco/Oakland, California and Seattle, Washington.   The
seminar registration fees are quite reasonable.  For additional information,
contact the ATC web site (www.atcouncil.org) or e-mail:atc(--nospam--at)atcouncil.org.

Hopefully, at least one attendee will ask at least one of the speakers at each
seminar questions concerning how to apply the provisions of FEMA 273, Section
2.11, Overturning to real example buildings.

The following Example Building is taken from the Building Seismic Safety
Council (BSSC) "Validation of the Design and Analysis Procedures and Criteria
Report", 1997, pertaining to the 75% Draft of FEMA 273.

The Example Building is a three story reinforced concrete bearing wall
building braced by reinforced concrete shear walls.  The Example Building is
braced by an 18" thick x 25 foot long reinforced concrete shear wall at each
end of the 30 foot high by 75 foot wide x 120 foot long building.

The calculated period of the building is 0.26 seconds.
The calculated weight of the building is 4,725 kips.

The "Pseudo Lateral Force" (Base Shear), V = C1*C2*C3*Sa*W, is V = 1.33 W,
which is calculated to be 6,284 kips.

This "Pseudo Lateral Force", distributed according to FEMA 273, results in a
force at the roof = 1571 kips, a force at the third floor = 1046 kips, and a
force at the second floor = 525 kips on each end shear wall.  These forces
produce a Mot (oveturning) = 73, 300 ft. kips.  The Mor (Moment resistive) due
to 90% of the tributary dead loads (wall's own weight and tributary roof and
floor loading = 81 lbs. / sq. ft.)  = 4,250 ft. kips.

According to the "principles of statics", the net Mot = 69,050 ft. kips, which
results in the shear wall edge tension force = 2,762 kips and an edge
compression force = 3,102 kips.

According to FEMA 273, Section 3.4.2.1, Mot can be reduced by a factor 'm' =
3,  which = 24,433 ft. kips.  The net Mot = 20,183 ft. kips produces shear
wall edge tension force = 807 kips and an edge compression force = 1,147 kips.

According to FEMA 273, Section 2.ll, Overturning, "Side-Bar", page 2-38,
unnumbered equation Q = 0.9QD + QE /Rot, where Rot = 6.0 for Life Safety,
results in a net Mot = 73,300  ft. kips / 6.0 minus 4, 250 ft. kips = 7,967
ft. kips.
This net Mot produces shear wall edge tension force = 319 kips and a
compression force = 659 kips.

QUESTIONS:
1. Which of these three sets of shear wall edge tension and compression forces
should be used in the design of the foundation for the Example Building?
2. Should some other method be used to calculate these tension and compression
forces?
3.  Do the final selected shear wall edge tension and compression forces
appear to be reasonable to be resisted in the Example Building?

The calculations and conclusions have been verifited by a retired San Jose
State University in a personal communication to me, dated October 29, 1998.

I would appreciate any "peer review" comments and responses from the FEMA 273
Seminar speakers and others concerning my interpretation of FEMA 273 and the
above results from my calculations.

Thank you for your consideration of my request.



Frank E. McClure      FEMCCLURE(--nospam--at)aol.com   November 2, 1998