Effects of bridge aging on bridge bearing lifetime demands

The life expectancy of bridge bearings is not well understood, causing difficulty for inspection, maintenance and replacement scheduling. Field inspections of bridge bearings are typically done every two years, but provide limited information on the remaining service life of the bearing. Characterizing life cycle demands on bridge bearings provides an initial step to help assess when they need to be serviced. While cyclical bearing demands are primarily caused by thermal effects and traffic loading, seismic events cause the largest displacement demands. However, due to aging infrastructure, it is not realistic to assume that bridges will be in their as-built condition when encountering an earthquake. Degradation with time has the potential to significantly impact the demands imposed upon bridge bearings during seismic events. This paper uses a deteriorative model, which captures the effect of reinforcement corrosion and the cracking and spalling of cover concrete, to examine the change in bearing seismic demands for aging multi-span concrete girder bridges. Monte Carlo simulation is then used to examine the change in expected lifetime seismic loading when bridge deterioration is considered. The expected seismic loading is combined with thermal and traffic loading to help characterize and quantify lifetime loading. The results can be used to propose fatigue loading protocols for us in future experimental and numerical studies to better predict bearing life expectancy, which is valuable information for bridge owners.