Evaluation of flood-resistant capacity of scoured bridges

The exposure of pier foundations owing to scour significantly reduces the foundation-bearing capacity and diminishes the flood-resistant capacity of a bridge. This paper proposes a nonlinear quasi-static analysis procedure for the performance of bridges with pile foundations under flow-induced loads for the evaluation on the flood-resistant capacity of scoured bridges. The Winkler beam model is adopted for the modeling of the pile-soil system, and the distributed hinge model is utilized to simulate the possible flexural failure of the piles. Soil springs with nonlinear p-y curves are used to represent the nonlinearity of the supporting soil. To demonstrate this procedure, a case study on the Shuang-Yuan Bridge in Taiwan was performed for various flood and scour conditions. This bridge was partially demolished in a major flood event caused by Typhoon Morakot in 2009. According to the analysis results, a possible scenario for the failure of the Shuang-Yuan Bridge is presented, and the proposed method is shown to give a reasonable assessment of the flood-resistant capacity of bridges with scoured pile foundations.