Stability of Simple Beam Subjected to Multiple Seismic Excitations

Abstract

This technical note analyzes the stability of a simple beam subjected to spatially varying random seismic excitations. It uses the stochastic average method to calculate the stability boundaries of a beam under various earthquake excitations. The structural responses are modeled as a two-dimensional (2D) Markov process representing the response amplitude and phase angle. The parametric random excitation is induced by the spatially varying multiple seismic excitations at the two supports. Only the second-order moment stability is considered in this study. Based on the average properties of highway bridges and an empirical ground motion coherency loss function, the stability boundaries of a simple beam subjected to multiple support excitations are calculated. It is found that the stability strongly depends on the beam properties such as the span length, vibration frequency, and damping ratio. It also depends on ground excitation intensity, propagation velocity, and the coherency loss between the multiple excitations.