Parametric Study of Bidirectional Vehicle–Bridge Interaction for Idealized Multi-Span Highway Bridge with General Boundary Conditions

The dynamic interaction between vehicles and bridges, particularly under bidirectional traffic conditions, poses significant challenges for structural response analysis. While previous studies have primarily focused on single-vehicle models or simplified bridge configurations, this study investigates the dynamic interaction behavior of bidirectional vehicles and a spring-supported multi-span bridge with general boundary conditions. A finite element-based vehicle–bridge interaction (VBI) model is established, and the coupled equations of motion are solved using a predictor–corrector precise integration procedure. The proposed method is first verified against an analytical solution and the Newmark-β method, showing good agreement in both vehicle and bridge displacement responses. A parametric study is then performed to examine the effects of vehicle meeting position, bidirectional vehicle speeds, vehicle mass, and support stiffness on bridge displacement and dynamic amplification. Graphical optimization further indicates that asymmetric speed control can expand the safe operating region and reduce the need for complete bridge closure under heavy traffic conditions. The proposed framework provides an efficient mechanical tool for evaluating bidirectional vehicle–bridge interaction and supporting the serviceability-oriented traffic management of spring-supported bridges.