Seismic Behavior of Pile-Group-Supported Bridges in Liquefiable Soils with Crusts Subjected to Potential Scour: Insights from Shake-Table Tests

One-g shake-table tests were conducted to characterize seismic demands and reveal failure mechanisms of pile-supported bridges in liquefiable soils with crusts subjected to different scour scenarios, namely no scour, partial scour, and complete scour of the crusts. To this end, reinforced concrete bridge models, each consisting of a single pier supported by a 2x2 pile group, were constructed and embedded into liquefiable soil profiles with a full crust or with a partial crust or without crusts to represent the studied three scour scenarios. Physical observations and characteristic soil and structural responses are interpreted first, followed by the primary focus on seismic failure mechanisms and kinematic and inertial effects on pile responses. Test results indicate that scour tends to strongly affect failure mechanisms of the studied bridges via shifting damage positions from pier bottoms to pile heads and from piles at crust-sand interfaces to pile heads. This tendency is against the current capacity design principle that piers should fail before pile foundations. Special attention should be paid to future seismic design of bridges undergoing scour and liquefaction. Furthermore, the kinematic effect is found more prominent before scour, whereas the inertial effect itself becomes more influential after scour.