Seasonal Freezing Effects on the Dynamic Behavior of Highway Bridges

Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, the bridge stiffness is also measurably increased in the winter months. Significant changes in the bridge pier boundary conditions due to seasonal freezing requires additional detailing to ensure a ductile performance of the bridge during the design earthquake event. This paper reports the latest results obtained from a project aimed at systematically investigating the effects of seasonal freezing on the seismic behavior of highway bridges in cold regions. Presented here are the results obtained from numerical simulation of the overall dynamic performance and field monitoring study of the bridge selected for study in this project. By using OpenSees computational platform, a three-dimensional FE model of the bridge foundation is established to investigate the impact of seasonal frost on the bridge substructure behavior. In the meantime, a bridge is instrumented with a network of accelerometers to monitor its dynamic and seismic behavior. Earthquake-induced vibration data have been collected and analyzed. The results show that seasonal frost has significant impact on the overall dynamic behavior of bridges supported by pile foundations in cold regions, and these effects should be accounted for in seismic design.