Recorded seismic response of Pacific Park Plaza. II. System identification

Journal of Structural Engineering
By:  and 



This is the second of two companion papers on the recorded seismic response of the Pacific Park Plaza building, in Emeryville, Calif., during the October 17, 1989, Ms = 7.1 (surface-wave magnitude) Loma Prieta earthquake. In this second part, the recorded data are analyzed in more detail by using system-identification techniques. The three-dimensional behavior and the coupled modes of the building are determined, and the effects of soil-structure interaction are investigated. The study shows that the response of the building is nonlinear at the beginning, and becomes linear after 17 sec into the earthquake. The dominant motion of the building follows an elliptical path oriented in the southeast-northwest direction. Some of the modes are complex, with nonproportional damping, and there are phase differences among modal response components. The fundamental mode of the building is a translation in the southeast-northwest direction at 0.4 Hz, with 13% damping. The wing displacements relative to the center core are large, about 50% of the center core displacements, and indicate significant torsion in the center core. The soil-structure interaction is characterized by a vibration at 0.7 Hz. This is believed to be the fundamental frequency of the surrounding soil medium. The rocking motions of the building are negligible.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Recorded seismic response of Pacific Park Plaza. II. System identification
Series title Journal of Structural Engineering
DOI 10.1061/(ASCE)0733-9445(1992)118:6(1566)
Volume 118
Issue 6
Year Published 1992
Language English
Publisher ASCE
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Structural Engineering
First page 1566
Last page 1589
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