Numerical simulation and damaged analysis of a simply-supported beam bridge crossing potential active fault

Abstract

Surface ruptures resulting from seismic faulting have the potential to inflict substantial damage to bridges straddling fault lines; hence, it is imperative to investigate the impact of ground motions documented on either side of fault rupture planes—termed as across-fault ground motion—on the seismic resilience of bridges. In this paper, the object of study is a three-span, simply supported beam bridge traversing a strike-slip fault. Utilizing the LS-DYNA finite element software platform, a sophisticated three-dimensional finite element model of the selected bridge is constructed, meticulously accounting for material damage nonlinearity and structural collision contact nonlinearity. A synthetic across-fault ground motion serves as the excitation for the seismic analysis of the bridge, systematically examining the influence of the fault-crossing angle (FCA), fault sliding rise time, and ground surface permanent rupture displacement on the dynamic response and seismic damage incurred by the simply supported beam bridge. The findings demonstrate that a diminutive fault-crossing angle (FCA) corresponds to an elevated risk of longitudinal beam collapse when a simply supported beam bridge does not intersect a fault vertically. The impact of the fault sliding rise time on the magnitude of seismic response and damage sustained by the simply supported beam bridge is relatively minuscule and can be neglected. Conversely, the ground surface permanent rupture displacement profoundly influences the dynamic response and seismic damage of the bridge. The emergence of fling-step pulses from the development of ground surface permanent rupture displacement amidst seismic activity induces a shift in failure mode-from the designer-intended bending failure to an unforeseen shear failure.