Conditional spectrum‐based ground motion selection. Part I: Hazard consistency for risk‐based assessments

Abstract

Summary:The conditional spectrum (CS, with mean and variability) is a target response spectrum that links nonlinear dynamic analysis back to probabilistic seismic hazard analysis for ground motion selection. The CS is computed on the basis of a specified conditioning period, whereas structures under consideration may be sensitive to response spectral amplitudes at multiple periods of excitation. Questions remain regarding the appropriate choice of conditioning period when utilizing the CS as the target spectrum.NOT THE PUBLISHED VERSION; this is the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation at the bottom of the page.Earthquake Engineering & Structural Dynamics, Vol. 42, No. 12 (October 10, 2013): pg. 1847-1865. DOI. This article is © Wiley and permission has been granted for this version to appear in e-Publications@Marquette. Wiley does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from Wiley. 2This paper focuses on risk-based assessments, which estimate the annual rate of exceeding a specified structural response amplitude. Seismic hazard analysis, ground motion selection, and nonlinear dynamic analysis are performed, using the conditional spectra with varying conditioning periods, to assess the performance of a 20-story reinforced concrete frame structure. It is shown here that risk-based assessments are relatively insensitive to the choice of conditioning period when the ground motions are carefully selected to ensure hazard consistency. This observed insensitivity to the conditioning period comes from the fact that, when CS-based ground motion selection is used, the distributions of response spectra of the selected ground motions are consistent with the site ground motion hazard curves at all relevant periods; this consistency with the site hazard curves is independent of the conditioning period. The importance of an exact CS (which incorporates multiple causal earthquakes and ground motion prediction models) to achieve the appropriate spectral variability at periods away from the conditioning period is also highlighted. The findings of this paper are expected theoretically but have not been empirically demonstrated previously.

An earthquake-source-based metric for seismic fragility analysis

“…Similar to the studies on ground-motion selection in Lin et al (2013b) and Lin et al (2013a), the SROM-based method selects just a small number of records from a large database of real or synthetic ground motions. In contrast to the aforementioned studies, the SROM samples are selected to match the probability law of the ground-motion records, rather than just the response spectra of linear SDOF systems.…”

“…One approach, known as incremental dynamic analysis, involves repeated scaling of seismic ground motions to increasing intensity measures until the specified damage state is reached (Vamvatsikos and Cornell 2002;Zareian and Krawinkler 2007;Goulet et al 2007). Another method for calculating fragility curves, known as multiple stripes analysis (Lin et al 2013b;Baker 2015), uses ground-motion records from a large dataset selected to be consistent with different spectral values of the response (Ozer and Akkar 2012;Baker 2011). The log-normal cumulative distribution function is commonly used as a parametric model for fragility curves (Singhal and Kiremidjian 1996;Baker 2007;Jalayer et al 2007).…”

Rintc Project - Assessing the (Implicit) Seismic Risk of Code-Conforming Structures in Italy

“…To select the ground motion records to be used as input for dynamic analysis, the conditional spectrum (CS) approach (e.g., [22]) has been considered. The CS provides the distribution of Sa T at any oscillation period (i.e., an elastic response spectrum) conditional on a given value of 1 Sa T .…”

Rintc Project: Nonlinear Analyses of Italian Code-Conforming Precast R/C Industrial Buildings for Risk of Collapse Assessment

“…A set of 20 records is selected [18] at each intensity level for the five sites and both the soil types. The records were selected by means of the Conditional Spectrum (CS) approach [19][20][21] at a reference period of 2.0 seconds, given the structural typology. 1000 2500 5000 10000 100000 Table 5 Return periods for 10 intensity levels Figure 5 Spectra of the records for Caltanissetta on soil A…”