Effect of Concrete Road Roughness on Dynamic Response of Girder Bridges

The dynamic response of highway bridges subjected to moving truckloads is observed to be dependent on dynamic characteristics of the bridge, vehicle dynamics, and road surface roughness profile. Road roughness and the bump at bridge entrance between bridge and concrete approach slabs are the major contributors to the dynamic amplification of stresses in bridge elements. The Bridge dynamic load is usually specified as an equivalent additional static load, and referred to as Dynamic Load Factor (DLF). There is a need to quantify the effect of road roughness on bridge response so it can be considered in bridge design codes. A three-dimensional computer model which uses Newmark-? integration, is presented to simulate the bridge-road-vehicle interaction system. The study focuses on the effect of road roughness on DLF. Power Spectral Density (PSD) is used to generate the profiles for computer. The results show that that DLF is highly dependent on road roughness, and different road profiles can lead to an 18% increase in DLF. The constant value, 1.33 for DLF, in the current AASHTO LRFD (1998) specifications, is still conservative compared to the results of this study, which takes into account very rough surfaces that are not usually considered in the design of new bridges.