Influence of Bridge Bearings on Mitigating Nonlinear Seismic Responses of Straddle-Type Monorail Trains

Straddle-type monorail systems (STMSs) are increasingly adopted as medium-capacity transit solutions to alleviate urban traffic congestion. However, their operational resilience during earthquakes is challenged by the low lateral stiffness of track beams and single-column piers, with critical components like bearings and piers vulnerable to elastoplastic behavior under seismic loads. To this end, this study proposes a MATLAB + OpenSees co-simulation framework to investigate nonlinear vehicle–bridge interaction (VBI) dynamics in STMSs subjected to seismic excitations. Validation shows high consistency with literature results, with Pearson correlations of > 0.81 and > 0.98 for bridge and train responses and relative errors of maximal values < 4%. Three types of bridge bearings—regular spherical steel bearing, lead rubber bearing (LRB), and friction pendulum bearing (FPS)—are compared to assess their influence on mitigating vibration responses. Both LRB and FPS effectively reduce lateral vibrations of the track beam and train, with maximum reduction rates reaching up to 60%. The shear forces and bending moments at the bottom of the piers are also substantially reduced by the isolation bearings, with reduction rates up to 50%. The proposed approach can be extended for nonlinear VBI analysis of STMSs under severe nonlinear excitations such as strong earthquakes, high winds, or collision loads.