Study on aerodynamic characteristics and stochastic vibration analysis during train passage over bridge under crosswind

The growing demand for high-capacity rail transit has led to the adoption of lighter and faster trains operating on long-span bridges, where strong crosswind-induced train–bridge interactions present considerable risks to operational safety. This study develops a stochastic analysis framework to assess the aerodynamic performance of train–bridge systems under crosswinds by integrating computational fluid dynamics with a coupled vibration approach. A three-dimensional interaction model is established using the k-omega shear-stress transport turbulence model to resolve complex flow fields and unsteady aerodynamic loads under high-speed conditions. The probability density evolution method is employed to solve the stochastic dynamic equations, quantifying system vibrations and evaluating running safety indices. Results reveal that the lateral response of the train–bridge system increases exponentially with wind speed. Owing to aerodynamic coupling between the moving train and crosswinds, both vehicle and bridge aerodynamic coefficients show significant sensitivity to increasing Reynolds numbers. Changes in cross-sectional parameters can cause force coefficient amplitudes to vary by over 40% compared to baseline values. Large bridge pylons induce notable aerodynamic shielding effects, where spatial pressure gradients between windward and leeward sides reduce the resultant aerodynamic forces across the coupled system by up to 50%. These findings offer valuable insight for the aerodynamic design and safe operation of long-span rail bridges in wind-prone regions.