Effects of Nonuniform Crosswinds in Valleys on Dynamic Responses of High-Speed Trains and Long-Span Suspension Bridges

Abstract

This study examined the influence of nonuniform wind fields in valleys on the dynamic responses of high-speed trains and long-span bridges. The wind field in a valley is considerably different from a theoretical uniform wind field in terms of mean and fluctuating wind characteristics because of the influence of the speed-up effect of crosswinds. The spatial nonuniformity of a valley wind field along a bridge span is equivalent to a “sudden change” load effect for running trains, which increases the complexity of the wind fields in the train–bridge system and may diminish the running performance of trains. To better understand the nonuniform characteristics of wind fields in valleys, a multipoint synchronous field measurement along the main girder of a long-span suspension bridge was conducted. Based on the measured wind field characteristics, a refined numerical wind field was established for conducting the coupling vibration analysis between train and bridge. It is shown that the valley induces an obvious nonuniformity in the mean wind speed, turbulence intensity, and turbulence integral along the bridge span. A higher mean wind speed and lower turbulence intensity occurs at the midspan of the main girder than at the two side spans. A refined numerical wind field can be established to identify the most unfavorable time for a train to cross the bridge from the perspective of the wind speed field experienced by the train. Compared with a uniform wind field, the nonuniform wind field has a more obvious effect on the lateral deformation of a bridge than on the vertical deformation. When a train crosses a bridge at an unfavorable time, the running safety of the train decreases, but the running comfort coefficient of the train is less affected. The limited influence of nonuniform crosswind on train-running comfort is caused by the difference of lateral bridge deformation between two wind fields.