A New Intensity Measure That Accounts for the Effects of Spectral Acceleration, Duration, and Spectral Shape

Abstract eng:
The effects of ground motion duration and the shape of the spectrum after the structure softens are not accounted for in structural design. The design code recommends that buildings be designed based on the spectral acceleration at the structure’s period from the maximum considered earthquake (MCE). Recorded ground motions scaled to the MCE spectral acceleration can result in a wide variety of nonlinear structural responses. To reduce the variation in structural response at a particular ground-motion intensity, a new intensity measure is formulated to account for the combined effects of spectral acceleration, ground-motion duration, and the response spectrum shape. The intensity measure includes a new measure of spectral shape that integrates the spectrum over a period range that depends on the structure’s ductility. The paper demonstrates the efficiency of the IM in predicting collapse of deteriorating single and multiple degree-offreedom systems. This efficiency is attributable to the inclusion of ground-motion duration and the ductility dependence of the spectral shape measure. Finally, the new IM’s efficiency is compared to several existing spectral shape intensity measures.

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