Modal and pushover analysis of concrete bridges with shallow footing subjected to seismic and scour loading

General scour is the process of uniform soil erosion around pier foundations due to water flow and can reshape the dynamic behavior of bridges. In this study, the dynamic characteristics of a typical shallow foundation concrete bridge was evaluated while affected by scour. To this end, a 3D finite element model was developed capturing the nonlinear behavior of critical elements. Modal analyses were conducted to observe the changes in dominant mode shapes and periods while the soil around bridge foundations is gradually removed. Pushover analyses were performed with different load patterns to assess the bridge strength at different levels of scour severity. Results showed that in shallow foundation bridges, the dynamic properties of the structure do not change unless an extreme scour severity case happens (i.e., soil erosion more than 90% of foundation depth). In such event, the flexibility of structure would notably increase, and mode shapes would significantly change.