Hydrodynamic loading characteristics of coastal twin box-girder bridges subjected to freak waves

Coastal bridges are highly vulnerable to extreme wave events, particularly freak waves generated by hurricanes and tsunamis. While most existing studies focus on single bridges, this work numerically investigates the hydrodynamic loads on twin box-girder bridges subjected to freak waves with specified parameters. The study first compares load responses between single and twin bridges with different submergence coefficients and spacings between the twin bridges. Results show that the forward bridge experiences similar forces to a single bridge, while the backward bridge can experience significantly amplified forces under close spacing, revealing critical interference effects between the two structures. Comparisons between regular and freak waves indicate that freak waves consistently induce higher loads, both for the single bridge and for twin bridges when accounting for structural interference. Finally, the effects of crest ratio, wave height ratio, and period on the freak wave forces acting on the twin bridges were investigated. The results demonstrate distinct loading patterns between the forward and backward bridges. These findings enhance understanding of wave-structure interactions and provide guidance for designing coastal twin bridges under extreme wave conditions.