Modeling Probabilistic Critical Earthquake Inputs for Structures Using the Site Response Spectra

This paper develops a reliability-based computational methodology for modeling nonstationary random critical earthquake loads on structures using the site response spectra.The power spectral density function and the envelope parameters of the ground acceleration are taken to be unknown and are computed such that the structural reliability index is minimized subjected to constraints reflecting known knowledge on the site seismicity.Specifically, bounds on the total energy, zero-crossing rate and entropy rate of theearthquake signal and positivity requirements are considered. These constraints are derived from the site response spectra. The formulation combines methods of structural reliability analysis, response surface fitting, FORM and nonlinear programming. Numericalillustrations on reliability-based critical earthquake inputs for elastic and inelastic framestructures are presented.