The response of the bridge to the assessment of flood damage is constrained by a restricted examination of soilspecific vulnerabilities and the hydrodynamic forces linked to local scour. The research study will, consequently, aim to address these knowledge gaps in assessing the structural susceptibility of bridges to flooding in very stiff clay (type B) and medium dense sand (type C) soil. This research aims to analyse the behaviour and response of the bridge model when subjected to varying depths of local scour across different soil types. To accomplish this objective, a three-dimensional numerical model is employed for a standard three-span reinforced concrete bridge. In the conducted experiment, a total of 192 scenarios were simulated, considering four distinct levels of local scour depth across two different soil types. The analytical results indicated a notable increase in pier displacement because of the augmented scour depth. The recorded displacement in medium dense sand exhibited a 42 percent increase because of the rise in scour depth. Consequently, it was determined that the impact of erosion caused by flooding on bridges spanning rivers must be accounted for when designing the bridges' foundation.

High-rise pile cap structures, such as sea-crossing bridges, suffer from long-term degradation due to continuous corrosion and scour, which seriously endangers structural safety. However, there is a lack of research on this topic. This study focused on the long-term performance and dynamic response of bridge pile foundations, considering scour and corrosion effects. A refined modeling method for bridge pile foundations, considering scour-induced damage and corrosion-induced degradation, was developed by adjusting nonlinear soil springs and material properties. Furthermore, hydrodynamic characteristics and long-term performance, including hydrodynamic phenomena, wave force, energy, displacement, stress, and acceleration responses, were investigated through fluid-structure coupling analysis and pile-soil interactions. The results show that the horizontal wave forces acting on the high-rise pile cap are greater than the vertical wave forces, with the most severe wave-induced damage occurring in the wave splash zone. Steel and concrete degradation in the wave splash zone typically occurs sooner than in the atmospheric zone. The total energy of the structure at each moment under load is equal to the sum of internal energy and kinetic energy. Increased corrosion time and scour depth result in increased displacement and stress at the pile cap connection. The long-term dynamic response is mainly influenced by the second-order frequency (62 Hz).

This study puts forward a reliability analysis for the bearing performance of piles subjected to the coupled action of chloride corrosion and scouring. A chloride diffusion model was constructed based on the stiffness degradation factor and Fick's law. The Monte Carlo simulation method, along with the consideration of the scouring effect of water flow on the pile foundation, was employed to assess the impact of key factors on the failure probability, considering both the bending moment and lateral displacement damage criteria. The results show that for the same exposure period, the failure probability increases as the bending moment, lateral and vertical loads, and seawater velocity increase; furthermore for the same conditions, the failure probability increases with longer exposure times. According to a particular case study, the mean bending moment, mean lateral and vertical loads, and seawater velocity all have an impact on the lateral displacement failure criterion, making it more sensitive than the bending moment failure criterion.

The effects of scour depth on the seismic responses of rock-socketed single pile foundations and 2 x 2 pile group foundations were investigated by shaking table tests, and the seismic performance and differences of these two foundation types were analyzed. The test results show that increasing scour depth causes liquefaction to occur earlier but also accelerates the dissipation of pore water pressure. Pile acceleration, pile top displacement, and pile bending moment all increase with increasing in scour depth. The pile top acceleration and amplification factor of the pile group increase steadily and linearly with increasing scour depth, while those of the single pile increase abruptly at the anchorage ratio of 4.6. The acceleration amplification effect is also susceptible to the types of soil layers and the stiffness of the pile body. The stability of pile group deformation is assessed to be superior to that of single pile based on the amplification inter line. The maximum bending moment of the pile body arises at the interface between saturated sand and strongly weathered granite, and its location does not shift with increasing scour depth. Increasing scour depth not only amplifies the adverse effects of seismic excitation on pile acceleration, pile top displacement, and pile bending moment but also amplifies the differences in seismic performance and liquefaction resistance of these two foundation types. Based on the research results, pile group foundations have better seismic performance than single pile foundations because of the load-sharing effect of the pile group under different scour depths. Therefore, pile group foundations can provide more stable support in scour-prone areas.