Nonlinear Soil–Abutment–Foundation–Structure Interaction Analysis of Skewed Bridges Subjected to Near-Field Ground Motions

This paper investigates the behavior of skewed highway bridges subjected to earthquake loading with strong velocity pulses. The behavior of bridges with skewed abutments in the longitudinal direction is strongly coupled by transverse loading. The interaction between skewed bridge abutment foundations and backfill has a strong impact on dynamic bridge response. While bridge structures may remain in the linear range during seismic loading, local nonlinear behavior at the abutment–embankment interface can cause significant nonlinear bridge structure response. Skewed bridge models are presented incorporating soil–abutment–structure interaction using nonlinear abutment springs. As a case study, a global three-dimensional nonlinear finite element model of the skewed and seismically instrumented Painter Street overpass in Rio Dell, California, with monolithic abutments was developed. The model used nonlinear foundation–soil interaction based on approach soil properties from geotechnical tests. A soil continuum finite element analysis was performed using constitutive hardening soil material to evaluate abutment backfill passive resistance considering backwall skew. The bridge response resulting from seismic ground motion records was compared with structure response data. The computer models represented fairly well the overall seismic response of the skewed bridge. Bent pile foundations had much less impact on overall bridge response than the abutments. Near-fault ground motions with high-velocity pulses generated asymmetrical impulsive loading and large displacements in transverse directions leading to significant rotation and residual deck displacement. These permanent structure displacements can control the design of the abutment seat width and shear keys and could exceed column displacement capacity and impose additional moment at the column not considered in current design.