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Analytical studies of a 49-storey eccentric braced building Safai, Aliyeh Jowrkesh

Abstract

The purpose of this research is to study the seismic behaviour of a well instrumented 49-storey steel frame building in San Francisco, California. The building was subjected to ground motions from the Loma Prieta earthquake (M[sub s] = 7.1) of October 17, 1989. During the earthquake the building response appeared to remain in the elastic range. In recent years, serious efforts have been undertaken to develop the concept of energy dissipation or supplemental damping into a workable technology, and a number of these devices have been installed in structures throughout the world. The focus of this study was a comparative study between dynamic behaviour of an instrumented 49-storey eccentrically braced frame building and dynamic behaviour of the same building with the eccentric braces replaced with a friction damper energy dissipation system. In addition to study of passive energy systems, a study of floor response spectra was also carried out, and the results were compared with the results using National Building Code of Canada (NBCC, 1995) and Uniform Building Code (UBC, 1997) regulations. Detailed three-dimensional linear and nonlinear dynamic computer analyses of the building was carried out for the eccentric braced and the comparative friction damped case, respectively. The results from the frequency domain system identification analyses was utilized to make verify the assumptions made and to match the results of numerical analyses with the recorded values. The results of this study showed that by performing a linear three-dimensional analysis, the actual response of the building during past earthquake could be reproduced with confidence. The hypothetical friction damped building behaved very well substantially reducing the storey force demand and relative storey displacements.

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