Near-field effects on seismically excited highway bridge equipped with nonlinear viscous dampers

Abstract

Near-field ground motions cause significant damage to highway bridges because of high peak ground accelerations and high peak ground velocities of long period pulses. To quantitatively assess the influence of near-field ground motions on seismically excited highway bridges, a ground motion model consisting of both pulse-type low frequency (near-field) and broadband frequency (far-field) components is proposed. In this model, the effects of the local site condition and the seismic source are taken into consideration by varying relative contributions of near-field pulse-type and far-field broadband random ground motion components in the synthetic ground motion. Extensive numerical simulations are carried out to quantify effects of pulse-type component and soil-structure interaction through a parametric study. Simulation results demonstrate that pulse-type components in ground motions amplify the response quantities of the highway bridge significantly over those by the broadband component. Nonlinear viscous dampers are effective in reducing all response quantities of the bridge to prevent serious damage to bridge bents and bearings.