Seismic Response of Imperial County Services Building in 1979

The Imperial County Services Building was severely damaged during the October 15th, 1979, Imperial Valley Earthquake. The vertical load carrying system and the structural systems used to resist lateral forces are described, and the response of the building is presented using reports of observed damage and acceleration histories measured with thirteen strong-motion accelerographs located throughout the building. In addition, base-shear and moment histories derived from measured accelerations are presented. Waveforms are examined for indications of when four first-story columns at the east end of the structure failed. Dynamic forces acting in either of the directions associated with the two primary lateral-forceresisting systems are examined to show that forces acting solely in one direction were not responsible for failure of four east-end columns. Response forces acting in both of the primary directions are considered simultaneously to develop a rationale for failure of east-end columns.