NONLINEAR DYNAMIC RESPONSE ANALYSIS OF WIND-TRAIN-BRIDGE COUPLING SYSTEM OF HU-SU-TONG BRIDGE

Geometric nonlinearity is one of the main nonlinear influence factors of long-span bridge structures. Its influence on the bridges and the running safety of trains cannot be ignored. The Hu-Su-Tong Yangtze River Bridge, the world's first super kilometer cable-stayed rail-cum-road bridge, is adopted as engineering background. Based on the in-situ wind field measurement, the actual wind field characteristics is extracted, and the spectral representation method is used to simulate the three-dimensional wind speed field of the bridge. The wind load model considering the complex nonlinear spatial characteristics is established. The bridge model is built up considering the geometric nonlinear factors such as the sag effect, beam column effect and large displacement effect. The whole-process iterative method is used to calculate the wind-train-bridge coupling vibration responses. The traffic safety analysis is given. The results show that considering the nonlinear factors increases the dynamic responses of the bridge and train to a certain extent and significantly increases the low-frequency component of the dynamic responses of the train. The large displacement effect has a greater impact on the structural response and the beam column effect has a less influence. Ignoring the influence of the nonlinear factors leads to inaccurate response analysis and unsafe evaluation. The wheel off-load index of the train exceeds the safety threshold when the train speed is 200 km/h and the wind velocity is more than 35 m/s, or when the wind velocity is 30 m/s and the train speed is more than 210 km/h. It means that the running safety of the train is threatened. The nonlinear wind-train-bridge coupling vibration analysis of the Hu-Su-Tong bridge has important scientific research significance and plays an important role in providing engineering guidance to ensure the safety of bridge structure and train operation.