Seismic Rocking Response of a Triangular Building Founded on Sand

A twenty-two story, triangular in plan, symmetrical, reinforced concrete building on the beachfront in Vin~a del Mar, Chile, was temporarily instrumented in August 1985 following the 3 March 1985 Central Chile earthquake ( M_s = 7.8) and aftershocks were recorded. Ambient and free vibration tests were also performed. The paper reports studies of the records of the responses of the building, the primary modes of vibration of the structure, its excellent performance during the earthquake and results from analyses using mathematical models and system identification techniques.