Conditional spectrum‐based ground motion record selection using average spectral acceleration

Abstract

Summary The use of a seismic intensity measure (IM) is paramount in decoupling seismic hazard and structural response estimation when assessing the performance of structures. For this to be valid, the IM needs to be sufficient;that is, the engineering demand parameter (EDP) response should be independent of other ground motion characteristics when conditioned on the IM. Whenever non‐trivial dependence is found, such as in the case of the IM being the first‐mode spectral acceleration, ground motion selection must be employed to generate sets of ground motion records that are consistent vis‐à‐vis the hazard conditioned on the IM. Conditional spectrum record selection is such a method for choosing records that are consistent with the site‐dependent spectral shape conditioned on the first‐mode spectral acceleration. Based on a single structural period, however the result may be suboptimal, or insufficient, for EDPs influenced by different period values, for example, peak interstory drifts or peak floor accelerations at different floors, potentially requiring different record suites for each. Recently, the log‐average spectral acceleration over a period range, AvgSA, has emerged as an improved scalar IM for building response estimation whose hazard can be evaluated using existing ground motion prediction equations. Herein, we present a recasting of conditional spectrum record selection that is based on AvgSA over a period range as the conditioning IM. This procedure ensures increased efficiency and sufficiency in simultaneously estimating multiple EDPs by means of a single IM. Copyright © 2017 John Wiley & Sons, Ltd.

Site dependence and record selection schemes for building fragility and regional loss assessment

“…To do so, we used the original algorithm developed for CS(SAT) [41] and its extended version for CS(AvgSA) [53]. To do so, we used the original algorithm developed for CS(SAT) [41] and its extended version for CS(AvgSA) [53].…”

“…Currently, in our opinion the most promising proposal is for employing the averaged spectral acceleration (AvgSA), whereby the logarithm of spectral acceleration is averaged over a range of periods [44][45][46][47][48], or other proposals for averaging spectral ordinates in the linear space [49,50]. Going one step further, Kohrangi et al [53] proposed a record selection method, termed CS(AvgSA), that improves upon the SAT-based CS approach, CS(SAT) [41], by changing the conditioning IM from spectral acceleration at a single period to AvgSA. Aiming instead at capturing the entire range of response that matters for loss estimation, Kazantzi and Vamvatsikos [52] proposed using AvgSA as a common, first-mode-period independent IM to assess the vulnerability for a whole class of buildings.…”

Soil‐Structure Interaction Effect on Fragility Curve of 3D Models of Concrete Moment‐Resisting Buildings

“…Eads et al showed that Saavg is generally more efficient and more sufficient and provides more stable collapse risk estimates than Sa( 1 ) after evaluating the efficiency and sufficiency of a similar IM for collapse prediction using nearly 700 moment-resisting frame and shear wall structures of various heights [20]. A recasting of conditional spectrum record selection which is based on Saavg over a period range as the conditioning IM was presented by Kohrangi et al [21].…”

Q-Factor Verification of a 6-Storey Concentrically Braced Frame via the Innoseis Risk-Based Approach

“…If considerable difference exists among the different first mode periods, one should consider using two different definitions of AvgSa, one for low/mid-rise structures (shorter periods) and another for high-rise ones (longer periods), for better fidelity. In any case, ground motion records need to be selected for each definition of AvgSa at a given set of sites [12,13], while mean hazard curves are required for each definition of AvgSa and at each separate site.…”