Performance-Based Strain Limits for Aging Spun Pile-Supported Wharves under Long-Term Corrosion and Seismic Loading

Aging spun pile-supported wharves are highly vulnerable to the combined effects of long-term corrosion and seismic loading, particularly in aggressive marine environments where chloride exposure progressively reduces material strength, stiffness, and ductility. This study develops a performance-based strain limit framework for evaluating the seismic safety of aging spun pile-supported wharves subjected to corrosion-induced material degradation. A fiber-based finite element analysis was conducted using nonlinear pushover procedures to simulate the seismic response of prestressed concrete spun pile wharf systems over a 75-year service period. Time-dependent deterioration was incorporated through reductions in concrete compressive strength, prestressing steel capacity, and section properties due to corrosion. Two representative pile-supported wharf configurations were analyzed to investigate the influence of structural arrangement on strain demand, plastic hinge formation, and residual seismic performance. The results show that long-term corrosion significantly decreases lateral load capacity by approximately 25–28% and reduces ductility ratios from about 4.50–4.70 in the initial condition to nearly 3.00–3.10 after 75 years of exposure. Concrete strain demand was found to exceed conventional serviceability thresholds and approach near-collapse levels in critical hinge regions, while prestressing steel strains remained below ultimate limits but exhibited reduced energy dissipation capacity. The findings demonstrate that conventional strain limits for uncorroded wharf structures may underestimate the damage potential of aging systems. Therefore, corrosion-adjusted strain limits are proposed to support performance-based seismic assessment, maintenance prioritization, and life-cycle management of marine infrastructure. This framework provides a practical basis for improving the resilience and safety of aging spun pile-supported wharves in corrosion-prone seismic regions.