Numerical Evaluation of Sea Salt Amounts Deposited on Bridge Girders

Abstract

It is important to evaluate the amount of airborne sea salt adhering to the structural members of a bridge for effective maintenance. This study sought to develop a method to estimate salt conditions on individual road bridge girders. The estimation was based on airborne sea salt concentrations obtained by on-site observations using new equipment, a steady flow of wind around the bridge with a computational fluid dynamics (CFD) technique, and the washing-out effect (detachment of adhered particles) resulting from raindrops. The estimated salt amounts adhering to bridge girders showed the same tendency in distribution on the seaward surfaces of the webs but not on the cliff-side surfaces. Additionally, the relationship between the amounts on the upper and lower surfaces of the bottom flanges was better reproduced by considering the effect of gravity on the sea salt particles. Consideration of the spatial distribution and changes over time of airborne sea salt concentrations and wind is needed to improve the estimation accuracy. The significance of the washing-out effect on the salt amount was also clarified.