Analysis Of Vehicle Safety Under Cross Wind On Long Span Bridges

Vehicle Safety has been identified as an issue not only concerned by vehicle manufacturer but also related to bridge designer and operator. This problem is involved in both bridge wind engineering and vehicle dynamics. There are several significant disadvantages for driving on long-span bridge: First of all, the wind speed on bridge deck is much higher compared with that on common road; Secondly, few shelters for vehicles under winds on bridge deck; Thirdly, wind instability and complex wind speed near the towers. Therefore, this paper try to make a proposal on evaluating method for the effective and safe driving strategy on bridge deck under crosswind. Soon relationship of extreme wind speed and vehicle speed is gotten and wind barrier measure is proposed and its effect is examined, which could be useful to bridge management department to carry out a proper traffic control measure under the circumstance of extreme wind speed or other disaster arouse by wind. The following researches will be achieved in this dissertation:1. The simplified uncoupled method for wind-vehicle-bridge system is proposed, furthermore, by using the example of Hangzhou Bay cable-stayed bridge, its availability is validated by comparison simplified analysis with coupling calculation.2. In order to have correct aerodynamic forces on vehicles, on the basis of reasonable classification of road roughness and various vehicles, wind tunnel tests are proceeded. Then major factors such as wind speed,vehicle speed and road roughness, which influent vehicle safety on roads under cross wind are examined using finite element transient dynamic method. Based on vehicle overturning and sliding criterion, relationships of three typical vehicles between accident wind speeds and vehicle speeds are concluded under static and driving condition.3. Long span bridge buffeting responses under various wind speed are carried out, in which modified superposition method of harmonic waves is taken for three-dimensional turbulent wind field simulation, flutter derivatives,aerodynamic admittance and towers participations are considered, ANSYS software secondary development is developed for calculation purpose.4. Vehicle driving safety on bridges under cross-wind, in which the bridge buffeting response and vehicle-bridge vibration are considered , is carried out . then based on vehicle overturning and sliding criterion on bridges under crosswind, some useful conclusions are drawn.5. A rigid partition model for Xihoumen bridge is built up at a scale ratio of 1:50. wind tunnel tests are taken to measure the surface pressure above the deck region near the tower for wind speed distribution to analysis the influence of local wind barriers and the tower to the local wind speed. Then an optimal wind barrier schemeis concluded.6. A lateral kinematical models of vehicle is proposed and lateral movements of three type vehicles are calculated . Then the efficiency of the wind barriers are further checked.