SAC Phase 1 Analytical Studies of Building Performance


Project Title:
Inspection, Damage, and Repair of Steel Frame Buildings following the Northridge Earthquake
Michael E. Durkin, Michael E. Durkin and Associates
Project Summary:
This project estimated the prevalence of steel frame building structural inspection, damage, and repair in portions of Los Angeles and Ventura counties following the 1994 Northridge earthquake. The study uncuded only buildings subjected to peak ground accelerations of .2 g or greater. Between late January an dearly March 1995, we reviewed agency data and surveyed building owners and design engineers to determine the frequency, types annd geographic distribution of damage to steel frame buildings. This investigation also determined the proportion of such buildings already inspected either by city agencies or by outside consultants, as well as the proportion where repair plans are being formulated or completed. Besides providing a statistical characterization of the above dimensions, the study provided locational information for non-obtrusive mapping of buildings (within the constraints of confidentiality).

An analysis of survey results found that eighty-three percent of participating buildings received visual inspections, but only thrity-eight percent had intrusive inspections aimed at finding connection damage and only eighteen percent had testing. At least eighteen of one hundred and thrity-three participating buildings suffered observed, steel frame damage. FIfty-five percent of tested buildings had connection damage. Steel frame damage was concentrated in buildings of between 200,000 and 300,000 square feet in size, in buildings constructed during the 1980's, and in buildings under five stories or between eleven and twenty stories in height. Buildings expposed to peak graound accelerations of .25 g to .35 g, to peak ground velocity of 20 to 25 cm. per sec, showed a relatively high, steel frame damage prevalence. Steel frame building damage, as well as the inspection and repair processes disrupted building operations. However, building owners used innovative strategies to monimize service interruption. At the time of the survey external forces influenced building inspections. On one hand, uncertainties, over proposed ordinances, delayed in-depth inspections. On the other hand, industry actors, such as lenders, insurers and out of state owners, required steel frame testing.

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SAC Steel Project
c/o Earthquake Engineering Research Center
1301 South 46th Street
Richmond, CA 94804
(510) 231-9477
FAX: (510) 231-5664