Estimation of floor acceleration demands in high-rise buildings during earthquakes

A simplified method to estimate lateral acceleration demands in high-rise buildings subjected to earthquakes is presented. In the proposed method acceleration demands are obtained by approximating the dynamic characteristics of the building with those of a continuous model consisting of a combination of a flexural cantilever beam and a shear cantilever beam. Closed-form solutions for mode shapes, period ratios and modal participation factors for the first six modes of vibration are presented. The method is evaluated by comparing peak floor acceleration demands and acceleration time histories computed with the proposed method to those recorded during earthquakes in six instrumented high-rise buildings. A comparison of floor spectra computed with the approximate method and spectra computed with recorded motions is also presented. Results indicate that the proposed method produces relatively good results with a very small computational effort and requires only a small amount of information about the building. Variations of accelerations demands along the height are closely examined in each building for each component. It is shown that the variation of acceleration demands along the height of high-rise buildings can differ significantly from that currently recommended in US seismic provisions for anchoring building nonstructural components. Copyright © 2005 John Wiley & Sons, Ltd.