Case studies on relative sufficiency of alternative intensity measures of ground shaking

In performance-based earthquake engineering, the uncertainty in the ground motion can be represented by probabilistic description of a parameter, known as the intensity measure (IM). Investigations are carried out herein for evaluating the predictive capability of a wide range of commonly-used scalar IMs for different demand parameters. To accomplish this goal, both the efficiency and sufficiency of the candidate IMs are taken into account. For the latter, the recently-proposed “relative sufficiency measure” is used which is on the basis of information theory concepts. This measure quantifies the suitability of one IM relative to another in terms of the amount of information gained (on average) in the representation of ground motion uncertainty. The relative sufficiency measure is calculated in an approximate manner based on a set of recorded ground motions. For corresponding evaluations, two existing RC frame structures are selected, and two sets of accelerograms, consisting of ordinary and pulse-like near-fault records, are used. It is concluded that the spectral acceleration at the first-mode period as well as a set of proposed structure-specified IMs, which are the modified versions of existing ones, are more informative, and intend to improve the correlations between the considered IMs and response quantities.