Behavior of scoured bridge piers subjected to flood-induced loads

Floods often result in significant damage to bridges with piers embedded in riverbeds. While the torrents induce strong lateral loads on bridges, they also sabotage the integrity of bridges by removing the sediment from around bridge foundations. The exposure of foundations substantially reduces the bearing capacity of bridges. The objective of this study is to examine the influence of scour on the behavior of bridge piers subjected to flood-induced loading. In addition, the effectiveness of retrofitting the pier foundation for improving the vulnerability of scoured bridge piers is studied. A complex, nonlinear three-dimensional finite element model that is capable of addressing interactions between bridge columns, pile foundations, soils, and water is developed. The developed model is employed to investigate the behavior of scoured piers during floods. The Shuang-Yuan Bridge that collapsed in a flood event due to excessive scour is adopted as a case study. The influences of scour depths and foundation retrofitting on the behavior of bridge piers are extensively investigated using various performance parameters, including the strength capacity, lateral stiffness, strength retention, and plastic failure mechanism. Furthermore, regression models are suggested to quantitatively represent the correlations between the scour depth and the performance parameters of piers. The foundation retrofitting work is found to be effective in improving the vulnerability of scoured piers only when the scour depth is less than a critical value. Finally, an index is suggested for assessing the safety of piers subject to scour during floods. (C) 2014 Elsevier Ltd. All rights reserved.