Simplified method for the assessment of the seismic response of motorway bridges: longitudinal direction—accounting for abutment stoppers

This paper investigates the effect of abutment stoppers on the seismic response of motorway bridges in the longitudinal direction. A rigorous 3D finite element model of a representative overpass bridge, including the entire bridge–foundation–abutment–soil system, is developed and used as a benchmark. The effect of abutment stoppers is shown to be significant, and must therefore be considered for proper simulation of the seismic response of such bridges. Subsequently, the resistance mechanism of abutments triggered when the bridge deck collides on the stoppers is examined. The model is first validated against theoretical solutions. The abutment cantilever wall is subjected to slightly—but crucially—different loading when the deck collides on the stoppers: the loading is applied at the top of the abutment without any rotational restraint. To gain insights on the key parameters affecting the abutment resistance to such passive loading at the top, a dimensionless analysis and a comprehensive parametric study are conducted, employing an equivalent 2D model of the abutment. The latter is validated against the results of a rigorous 3D model. Based on the results of the parametric study, a simplified model accounting for the effect of abutment stoppers is developed. Its efficiency is assessed on the basis of slow-cyclic pushover and nonlinear dynamic time history analyses, using the full 3D model as a benchmark. Overall, the extended simplified model is shown to offer a reasonable approximation (excellent for cohesive soil) of the seismic performance of typical motorway bridges in the longitudinal direction.