Dynamic Effect of Vehicles on Multispan Pre-Stressed Concrete Bridges over Rivers

Abstract

Dynamic response has long been recognized as one of the significant factors affecting the service life and safety of bridge structure. Even though considerable research, both analytical and experimental, has been devoted to dynamic behavior, the identification and extent of the controlling parameters that govern dynamic response have still not been clearly identified. On the other hand, under the current design loads, dynamic effects taken into account by increasing the static load by an impact factor, I, which is a function only of the bridge loaded length and does not distinguish between simple and continuous bridges. Also the important factors affecting the bridge dynamic response such as the vehicle speed, the vehicle weight and the pavement surface roughness are not considered by these codes. Therefore, the need of studying the actual dynamic behavior of highway bridges under traffic loads to evaluate the accuracy of the impact factors given by codes is strongly arises. Much of previous research works concerned with evaluating the dynamic response of single span bridges. The primary objective of this research is to develop a finite element bridge model that can accurately predict the static and dynamic responses of multispan highway bridges. Hence, to understand the dynamic behavior of this type of roadway bridges under traffic loads, two study cases of roadway prestressed concrete bridges are analyzed and their static and dynamic responses are investigated. The highway live loads and the impact formula given by the American bridge design code are considered in this study. The accurate dynamic factors estimated from the static and dynamic analysis of the investigated bridges are plotted against the approximate values of the impact factor given by the design code.