Correlation of spectral acceleration values in Iranian ground motions
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Ó Indian Academy of Sciences (0123456789().,-volV)(0123456789( ).,-volV)
Correlation of spectral acceleration values in Iranian ground motions REZVAN MOADDAB1, VAHID JAHANGIRI2 and HAMZEH SHAKIB3,* 1 Tarbiat 2
Modares University, Tehran, Iran. Department of Civil Engineering, Faculty of Engineering, University of Mohaghegh Ardabili, Ardabil, Iran. 3 School of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran. *Corresponding author. e-mail: [email protected] MS received 6 May 2019; revised 15 April 2020; accepted 14 May 2020
Spectrum compatibility is commonly used as a tool for ground motion record selection in order to perform dynamic analysis. Conditional mean spectrum calculation, which can be used as a target spectrum, requires obtaining correlation coefBcients between spectral acceleration values at multiple periods. To date, the correlation coefBcients have not been evaluated exclusively from ground motions recorded in Iran. This study represents results obtained from the calculation of correlations for spectral acceleration values from Iranian ground motion data and Zagros and Alborz-central Iran seismic regions, separately. The obtained results can be used for conditional mean spectrum calculations at Iranian sites. The observed correlation coefBcients for Iranian records are compared to the correlations developed from the Western United States ground motion data. It is seen that correlation coefBcients obtained from the Western United States ground motion data are less than the ones calculated in the study and therefore would cause further reducing of the target spectrum of interest. Keywords. Correlation; spectral acceleration; Iran; ground motion; epsilon.
1. Introduction The Brst traditional step for predicting seismic response of structures using dynamic analysis is selecting ground motion records in which their response spectra match a target response spectrum, and using those records as input motion (Baker 2011). The target spectrum is usually deBned by code provisions or is uniform hazard spectrum (UHS) computed directly through a probabilistic seismic hazard analysis (Katsanos et al. 2010). Conditional Mean Spectrum (CMS) can be used as target spectrum and has preferred to UHS by some researchers (Baker 2011) because UHS for ground motions selection may be conservative since it predicates that high spectral values
will occur at all periods within a single ground motion. CMS calculation needs knowing of correlation coefBcient values between spectral acceleration values at multiple periods (Jayaram et al. 2011). Baker and Cornell (2005) presented relations for correlation coefBcients for cases with different periods but the same orientation, and cases with differing periods and orientations and multi-component ground motions. Baker and Cornell (2006) empirically evaluated correlations between spectral accelerations with differing orientations or periods and developed approximate equations for their estimation. It was concluded that correlations of spectral accelerat
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