Investigation of two buildings shaken during the 19 September 1985 Mexico earthquake

The investigation described two buildings that suffered very little damage during the 1985 earthquake. Both buildings suffered extensive damage during a moderate earthquake that occurred in 1979, and both were repaired and strengthened using structural steel and reinforced concrete elements prior to the 1985 quake. Both buildings were located in the region of the city that experienced the heaviest damage, and both were in the height range (12 and 10 stories) where damage or collapse might have been expected. The objectives of the study are to determine why the buildings performed well, to evaluate the role of the structural steel strengthening systems in this excellent performance, and to evaluate and recommend similar retrofit schemes for U.S. practice. Findings are summarized.