Rheological-dynamical analogy for analysis of low cycle fatigue in seismically isolated regular bridges

Abstract

© 2019 Elsevier Ltd This paper examines low cycle fatigue in seismically isolated regular (SIR) bridges, taking into account the steady-state vibrations due to the lateral force of vehicles or any other lateral impacts of a permanent character. Bridges are modeled as two-degree-of-freedom (TDOF) systems in which the force presents sinusoidal impact on the centre of gravity of the bridge superstructure. Inelastic stiffnesses and modal damping ratios for the column and isolation bearing are obtained using the rheological-dynamical analogy (RDA). The background of this inelastic theory is presented in the framework of a mathematical-physical analogy between the rheological model of viscoelastoplastic (VEP) material and dynamical model with viscous damping. To estimate quantitatively the influence of isolation material characteristics on damping, corresponding frequency response functions for bent column and isolation bearings in bridges are analyzed. In addition, the paper develops the real damping matrix, which includes effects of damages due to fatigue, using the modal damping matrix and taking account of mode orthogonality.