Influence of Curvature, Skew Angle, and Bearing Restraint on the Seismic Performance of Curved Steel Girder Bridges

Curved and skewed steel girder bridges are widely used in highway interchanges, urban flyovers, and constrained transportation corridors where geometric alignment cannot be satisfied by straight bridges. However, the combined presence of horizontal curvature, support skew, bearing directional restraint, and abutment–backfill interaction produces a highly coupled seismic response that is not fully represented by simplified straight-bridge analysis assumptions. This study investigates the seismic performance of a curved and skewed steel I-girder bridge with emphasis on the interaction between spherical bearings and abutment restraint. A real three-span continuous curved steel I-girder bridge located in Pennsylvania, USA, is adopted as the reference case. The bridge has a horizontal radius of curvature of 178.49 m, three unequal spans of 23.2 m, 30.1 m, and 22.7 m, five ASTM A572 Grade 50 steel plate girders, 2.39 m girder spacing, and skewed abutments varying from 29° at the south abutment to 52° at the north abutment. (ResearchGate) A three-dimensional nonlinear finite-element modelling framework is proposed in which steel girders are represented using spatial frame elements, cross-frames using truss elements, the composite concrete deck using equivalent beam–shell action, spherical bearings using zero-length nonlinear link elements, and abutment–backfill resistance using compression-only nonlinear springs. The objective is to identify how bearing restraint direction, skew angle, curvature-induced torsion, and abutment mobilization jointly influence girder displacement, bearing rotation, deck pounding tendency, abutment force demand, and residual displacement. Published studies on similar curved and skewed steel bridges indicate that bearing response depends strongly on the interaction between excitation direction and bridge curvature; spherical bearings may experience slight-to-moderate damage when rotations exceed typical bearing clearance limits under seismic loading. (ResearchGate) The study shows that the critical seismic demand in curved and skewed steel girder bridges should not be interpreted only through longitudinal and transverse bridge axes. Instead, the response must be evaluated in curved-longitudinal, curved-transverse, skew-longitudinal, and skew-transverse directions because these directions activate different combinations of bearing sliding, abutment compression, girder torsion, and cross-frame force transfer. The manuscript contributes a component-level interpretation of coupled bearing–abutment behavior and provides modelling recommendations for nonlinear seismic assessment of irregular steel girder bridges.