ABSTRACT
The purpose of this paper is to present the results of a study of the seismic behaviour of two well-instrumented, tall steel frame buildings in Los Angeles, California. These buildings are within a few blocks of each other and have been subjected to ground motions from several earthquakes, among which the most significant are those from the 1994 Northridge earthquake. Though the buildings share many characteristics, each has a different structural lateral force resisting system. While one building relies on a perimeter tube system the other building relies on a spine structure with outrigger moment frames. Spectral analyses were used to determine that each building underwent a similar ground motion; hence, a meaningful comparison of building responses was made. Since the response of each building was mainly linear elastic it was possible to identify its linear dynamic characteristics by means of modal identification. The results of this study showed that although the buildings were subjected to the same level of ground shaking their different structural systems resulted in remarkably different building response. The differences and similarities of these responses are presented and discussed in this paper.
