Technically referred to as "soft/weak story and/or open-front wood-framed" buildings, soft-story wood-frame buildings typically have large openings on the ground floor, and many walls in the upper floors. Typically, these are apartments and condominiums that have parking under buildings, or open commercial space on the first floor, making this story "weak" or "soft" and likely to lean or even fall over in earthquakes. Per US Geological Survey Study in 1992, seven soft-story residential buildings and another 65 were moderately to severely damaged in the Marina District during the Loma Prieta Earthquake in 1989.
In conjunction with our own seismic mitigation efforts, the Department of Building Inspection has engaged the Applied Technology Council (ATC) to continue the Community Action Plan for Seismic Safety (CAPSS). As part of this project, ATC will evaluate various mitigation programs for soft-story wood-framed residential buildings that will consider not only seismology and structural engineering, but also socio-economic impacts. The goal is to develop a community-backed seismic mitigation ordinance to address these soft-story wood-framed residential buildings.
For additional seismic strengthening/retrofit information on Soft-Story, Wood-Frame Residential Buildings, contact William Strawn, Communications Officer of the Department of Building Inspection, (415) 558-6250 or email him at William.Strawn@sfgov.org.
Administration Bulletin AB-094
CAPSS Soft Story Report
New Legislation (Ordinance No. 54-10) Effective April 19, 2010
Related Articles / Links:
New Mandatory Retrofit Program for Soft Story Buildings
New Legislation On Soft-Story Wood-Frame Buildings - April 21, 2010
Mayor Newsom Announces Legislation to Improve Seismic Safety, read more ….
Mayor Newsom Executive Directive 08-07 on Seismic Strengthening of Soft Story Buildings (pdf)
Local Earthquake Panel Returns From China - August 18, 2008
U.S. Geological Survey Professional Paper 1552-F - The Loma Prieta, CA, Earthquake of October 17, 1989 - Marina District (pdf)
U.S. Geological Survey Fact Sheet 151-99 - Understanding Earthquake Hazards In the San Francisco Bay Region - Progress Toward a Safer Future Since the 1989 Loma Prieta Earthquake.
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