Soft story building

A Soft story building is a multi-story building whereby one or more floors have windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall would normally be required for stability as a matter of earthquake engineering design.cite news|url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/06/29/MNDD110U2E.DTL|title=S.F. leaders ignore weak buildings' quake risk|author=Robert Selna|publisher=San Francisco Chronicle|date=2008-06-29] [cite web|url=http://www.quake06.org/quake06/best_practices/IMSSB.html|title=Best Practices:Inventorying Multi-family Soft-Story Buildings:Cities of Berkeley, Campbell, Fremont, San Leandro|publisher=Earthquake Engineering Research Institute] A typical soft story building is a several-story apartment building located over a parking garage or series of retail businesses.

in a phenomenon known as soft story collapse. The inadequately-braced level is relatively less resistant than surrounding floors to lateral earthquake motion, so a disproportionate amount of the building's overall side-to-side drift is focused on that floor. Subject to disproportionate lateral stress, and less able to withstand the stress, the floor becomes a weak point that may suffer structural damage or complete failure, which in turn results in the collapse of the entire building.

Soft story failure was responsible for nearly half of all homes that became uninhabitable in California's Loma Prieta Earthquake of 1989, and was projected to cause severe damage and possible destruction of 160,000 homes in the event of a more significant earthquake in the San Francisco Bay Area, California. [cite news|url=http://realtytimes.com/rtpages/20031106_softstory.htm|publisher=Realty Times|date=2003-11-06|title=Earthquake Planner Warns Of "Soft-Story" Dangers|author=Broderick Perkins] As of 2008 few such buildings in the area had undergone the relatively inexpensive seismic retrofit to correct the condition.

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