Degradation mechanisms and long-term performance analysis of pile-group cap structures in sea-crossing bridges under corrosion and cyclic loading

Abstract

Pile-group cap structures of sea-crossing bridges are exposed to marine chloride-induced corrosion and repeated lateral wave loading during their long-term service, which progressively deteriorates their structural performance. This study combines 1:10 scaled model tests with time-dependent finite element analysis to investigate the degradation mechanisms and long-term performance of pile-group cap structures. Three scaled specimens were first corroded to different degrees (0%, 14.79%, and 24.95%) and then subjected to low-cycle lateral loading. Based on the experimental observations, a refined finite element model incorporating corrosion-induced material degradation and bond-slip effects was established and validated, and then extended to a prototype elevated pile-group cap structure of the Donghai Bridge by considering time-dependent material degradation and pile-soil interaction. The results showed that, relative to the uncorroded specimen (CT-0), corrosion shifted the critical damage zone from the pile bottom toward the pile-cap connection within the splash zone and reduced the yield, peak, and ultimate loads by up to 17.08%, 17.43%, and 15.14%, respectively. For the prototype structure, the long-term degradation was governed mainly by progressive corrosion-induced material deterioration, and tended to shift from load-carrying capacity loss toward more pronounced stiffness deterioration and plastic damage accumulation once the corrosion level exceeded approximately 30%. The proposed approach provides a basis for life-cycle assessment and maintenance of sea-crossing bridge structures.