Seismic Response from Centrifuge Model Tests of a Scoured Bridge with a Pile-Group Foundation

Abstract

A series of seismic centrifuge tests were performed on an RC girder-type bridge with a 3 × 3 pile-group foundation embedded in dry sand to investigate the seismic behavior under various scour conditions. Based on the equivalent primary period and mass, the bridge plate was reduced to a lumped iron block supported by a single pier. The laminar shear box was excited in three earthquake events and one white noise event. The test results show that the bending moment at the pile head and the acceleration at the pile cap both increase significantly with increasing scour depth, which is a potential failure mode in practice. The maximum bending moment, which generally occurs under the soil surface at a distance of approximately 1.9–2.2 times the outer diameter of the pile, is the largest in the corner pile and the smallest in the inner pile. The results show that the maximum bending moment is augmented 63.5% at most by scour. The acceleration response and dominant frequency of the model were noticeably influenced by soil nonlinearity. However, the damping that soil in the far field provided to the bridge system considering soil–structure interaction (SSI) was negligible and has little influence on the system frequency. These observations suggested that measures should be taken to meet the bending moment demand of the pile increased by scour and provided some guidelines for the aseismic design of the bridge and a benchmark for further theory analysis.