Simulation of Hazard Consistent Accelerograms Compatible With Target Uhs and Application To the Computation of In-Structure Floor Spectra

Abstract eng:
The Performance-Based Earthquake Engineering is becoming the state of the art for risk-informed decision making. In the nuclear domain, the Seismic Probabilistic Risk Assessment (SPRA) methodology has become the most commonly used approach for the evaluation of seismic risk and is now applied worldwide. In current practice, a set of ground motion is often simulated to comply in its mean with the target Uniform Hazard Spectrum (UHS). This can be considered as conservative since the UHS constitutes an envelope: it combines various scenarios to yield a target spectrum with uniform annual rate of exceedance for all spectral frequencies (or equivalently periods). Lin, Haselton & Baker recently proposed an innovative ground motion selection procedure that allows to obtain sets of hazard consistent time histories that allow to comply with prescribed UHS target spectra. It is based on the derivation of conditional spectra that not only matches the uniform hazard spectrum (UHS) at a conditioning frequency but also represents the spectral shape associated to a single earthquake scenario more realistically. The present work proposes a new way to obtain a pertinent ground motion set by simulation and combining the conditional spectra at various spectral frequencies. The time histories are simulate for a number of conditional target spectra using a stochastic model. The simulated ground motion possess the advantage that a close fit to target conditional spectra can be obtained, without record scaling. A great number of conditional ground motion can be simulated at low cost. Moreover, the simulation facilitates the definition of 3D motion that comply with the target. The methodology is assessed by the computation of in-structure floor response spectra. The floor spectra are an input used for the evaluation of seismic fragility curves in the framework of SPRA.

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