Mesoscopic statistics-based probability characteristics of chloride transport and reliability-based corrosion initiation life of bridge tower

Chloride-induced corrosion involves multiple factors and uncertainties. This study focuses on the probabilistic and multifactorial prediction model for the reliability and service life of reinforced concrete structures in marine environments. We present a new probabilistic framework to quantify the uncertainty of chloride transport by mesoscopic statistics and Spearman correlation analysis and develop a modified chloride transport model, incorporating multi-factors such as time dependence, admixture usage, temperature, relative humidity, stress level, freeze-thaw cycles, chloride binding capacity, aggregate volume fraction, aggregate particle size, and concrete deterioration. Taking the Shenzhen-Zhongshan Bridge as an example, by considering the chloride diffusion coefficient, concrete cover thickness, convection zone thickness, critical chloride concentration, and surface chloride concentration as random variables, the first-order reliability method (FORM) was employed to determine the time-variant reliability index and service life of the example bridge in different environmental conditions, encompassing atmospheric, splashing, tidal, and submerged zones. The sensitivity of the time-variant reliability to these random variables and the impact of the non-random variables on the reliability index were investigated quantitatively and comparatively. The findings reveal significant temporal and spatial variability in chloride diffusion coefficients due to the random arrangement of aggregates within concrete. The study demonstrates that concrete cover thickness and chloride diffusion coefficient are the most influential variables on structural reliability and emphasizes the substantial impact of admixtures, concrete deterioration, and environmental factors on the time-variant reliability. This research offers a significant reference in the reliability design, safety assessment, and maintenance of concrete structures in chloride-rich environments.