Performance and operational allowable speed limit for vehicles on cable stayed bridges

Abstract

The ever increasing numbers of fatal vehicle accidents worldwide on cable-stayed bridges under serviceable wind conditions, has rung the alarm bells for engineers to consider the safety issue in an operation level. The new generation of structural designs also involves the efficient and comfortable use of the structure by the end user. When this ‘design for the user’ concept is applied to bridges, investigation of vehicles travelling on long span bridges subjected to strong wind attacks not only allows the designer to have more understanding about the actual performance of a bridge at the operation level, but the safety and comfort of the drivers can also be studied. However, reliability analysis on a vehicle-bridge-wind system is such a time consuming process that it is usually considered infeasible in actual practice, especially when dealing with highly non-linear cable-stayed bridges. This study has constructed a general, yet efficient, vehicle stability analysis framework which makes possible the estimation of the maximum allowable vehicle velocity on cable-stayed-bridges subjected to different wind intensities. Non-linear properties such as the cable sag, geometrical non-linearity and wind induced buffeting and fluttering effects are studied and implemented into the analysis framework. In addition, the numerical simulation procedure is optimized using the partial iterative process (PIP) and the continuous simulation technique (CST), which can significantly reduce the time needed for performing the reliability analysis. The result of the numerical example demonstrated that both high-sided vehicles and small vehicles are likely to undergo vehicle instability problems on cable-stayed bridges subjected to wind loading. It is also suggested that the allowable speed limit for vehicle travelling on cable-stayed bridges are significantly lower than the limit on box-girder bridges. Besides, under serviceable wind loadings, the stability of a vehicle depends very much on the speed of vehicle, the roughness conditions on the deck and the degree of the coupling effect between the bridge and the vehicle.