Incremental Analysis for Seismic Assessment of Bridge with Functional Bearing System Subjected to Near-Fault Earthquake

A bridge with the functional bearing system, where sticking-sliding mechanism of rubber bearing reduces the force transmission between the substructure and the superstructure, shows viscoelastoplastic behavior. In the present paper, we show a simplified two-degree-of-freedom (2DOF) model for a bridge with the bearing system containing Coulomb’s friction element that displays mechanical behavior including the sticking (viscoelastic) and the sliding (viscoplastic) modes and we arrange its mathematical formulation into a two-phase framework which is a well-implemented form for incremental analysis. Solutions of the two-phase system are explored thoroughly and the exact solution of on-phase under piecewise constant input is obtained. Furthermore, we discuss on–off switching criteria of the bridge bearing system and propose an algorithm, including off-phase (viscoelastic) module, on-phase (viscoplastic) module, pull-back module, admissible condition, and straining condition, to simulate responses of the bridge bearing system. Based on the proposed algorithm, the assessment of the bridge with the functional bearing system which undergoes the near-fault earthquakes was made by investigation of the influence of five kinds of design parameters.