Investigating the Influence of Scouring Depth on the Seismic Response of Concrete Bridges with Deep Foundations

This study investigates the impact of local scour—a key issue that undermines bridge foundations—on the seismic behavior of concrete bridges with deep foundations. Three bridge types were analyzed: (۱) continuous box-girder bridges with integral piers, (۲) multi-span simply supported (MSSS) concrete girder bridges, and (۳) multi-span continuous (MSC) concrete girder bridges. After conventional design, modal analysis assessed changes in fundamental period and mode shape due to scour, followed by nonlinear modeling and incremental dynamic analysis (IDA) in OpenSees, with results shown as fragility curves. Findings reveal that short-span box girder bridges are most sensitive to scour, while MSSS bridges are least vulnerable due to their articulated superstructure. MSC bridges, though less sensitive to scour, showed the smoothest fragility curves, indicating generally lower seismic vulnerability. Notably, vulnerability increases most sharply at the initial stages of scour depth, then grows more gradually as scour deepens.

Keywords:

Concrete Bridges , Deep Foundations , Scouring , Nonlinear Analysis Time-History Analysis , Design