Time-dependent seismic fragility analysis of corroded pile-supported wharves with updating limit states

Abstract

Pile-supported wharves, as one of the main components in marine harbor systems, are subjected to multiple hazards such as earthquakes and corrosion during their lifetime. In this paper, the corrosion initiation time due to chloride ion diffusion (using both the deterministic and probabilistic approaches), temperature and humidity variations are calculated for various steel materials in the typical pile-supported wharf of port Los Angeles. Various deterioration sources such as reduction in the ultimate strength and strain of prestressed strands and concrete compressive strength are simulated. The updating limit state functions are identified by nonlinear static analysis. Finally, the time-dependent fragility curves are developed using incremental dynamic analysis. Results show that corrosion considerably reduces the seismic performance due to both structural strength and ductility over the life cycle of the wharf. It also causes brittle fracture, a sudden and complete failure of the corroded piles towards the end of the structure’s life cycle. Finally, a set of analytical models is proposed to estimate the median of the aging fragility functions with a nearly constant dispersion.