Strong Motion Instrumentation of Buildings

A comparison of the recorded structural earthquake response of a building and its predicted response by dynamic analysis provides vital information to structural designers on the effectiveness of current methods of dynamic analysis. There have been a number of previous studies of this nature, but only a few have paid attention to investigating the three-dimensional nonlinear dynamic behaviour of instrumented tall buildings. The purpose of this paper is to study the seismic behaviour of a well-instrumented 52-storey steel frame building in Los Angeles, California. This building has been subjected to ground motions from several earthquakes among which the 1991 Sierra Madre earthquake and the 1994 Northridge earthquake were selected in this study. During both earthquakes the building responses appeared to be in the linear range. Frequency domain analyses of the recorded motions from these two earthquakes were conducted to determine the dynamic characteristics of the structure. Three-dimensional nonlinear dynamic computer analyses were then employed to evaluate the response of the structure induced by severe shaking. The results of this study show that by performing a linear three-dimensional analysis, the real response of a building during past earthquakes can be reproduced with confidence. By further performing a nonlinear three-dimensional analysis, the state and sequence of damage can also be predicted. The Nonlinear Static Procedure (pushover analysis) generally excludes higher mode participation, which can be important for high-rise buildings subjected to certain types of ground motions. Improvements to this procedure were explored.