Analysis of dynamic response and failure mechanism of a box-girder superstructure with lateral block under fluid-structure coupling

The resistance of coastal bridges to extreme wave hazards has been a primary focus for many researchers, as these structures often face severe threats from waves. However, research on disaster-resistant measures for box- girder superstructure remain limited. The dynamic response of box-girder superstructures with lateral blocks under solitary waves is investigated in this study. It is crucial for coastal bridge to resist extreme wave hazards. A two-dimensional model, incorporating a numerical wave flume and a simplified box-girder model with lateral blocks, is introduced. The study delves into the effects of solitary waves at varying heights on the box-girder superstructure with lateral blocks. Furthermore, it explores the dynamic responses of the box-girder superstructure at different submersion coefficients and investigates potential failure modes, such as sliding, bearing deformation failure and unseating failure between the superstructure and the bearings, as well as the accompanying shear failure of the lateral blocks. Comparisons are conducted between box-girders without lateral blocks and their counterparts with lateral blocks, while evaluating the influence of lateral blocks on the superstructure across various levels of stiffness. The findings indicate that: (1) The installation of lateral blocks significantly improves the survivability of box-girder under extreme wave conditions, particularly by greatly lowering the probability of overturning failure. (2) The effectiveness of the lateral block in protecting the box- girder superstructure decreases when submerged, and this effect diminishes with a decrease in submersion coefficient. (3) The enhancement of lateral block stiffness can effectively mitigate the horizontal displacement of the box-girder superstructure and thereby improve its safety in the final state.