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Evaluation of current seismic design equations for nonstructural components in tall buildings using strong motion records


Saeed Fathali, Rutherford and Chekene, San Francisco, CA 94105, USA.



A recently completed California Strong Motion Instrumentation Program (CSMIP) data interpretation project used recorded ground and floor motion data to evaluate a key ASCE/SEI 7-05 (and 7-10) equation for seismic design of acceleration-sensitive building nonstructural components. CSMIP motions from 73 earthquakes recorded in 151 fixed-base buildings were used in the evaluation. An improved equation was developed with two categories of revisions. First, the current code formula considers a linear relationship between the peak floor acceleration (PFA) and the relative height of the component in the building with a roof PFA that is three times that of the peak ground acceleration. The analyses of the recorded motions showed that improved results could be obtained by using a nonlinear relationship and by considering both the building approximate period, Ta, and the level of ground motion. Second, the code formula considers a component amplification factor, ap, that takes values between 1.0 and 2.5 depending on the flexibility of the nonstructural component. Analyses showed that component amplification factor can be better represented using a three-segment spectrum composed of a linear rise from 1.0 to maximum value of ap at short periods, a flat segment with the maximum value of ap at medium-range periods and a nonlinear decaying segment at longer periods. The shape and amplitude of the spectrum were found to vary depending on Ta. This paper evaluates tall buildings with at least 15 stories using the proposed equations and confirms that the revisions provide improvements in matching design equations with recorded response. Copyright © 2011 John Wiley & Sons, Ltd.