2013 Volume 62 Issue 11 Pages 420-425
Considering that Cl－ influences corrosion rate of girders of steel bridges, precipitation rate of air-born salt is used to discuss the stability of steel bridges in a corrosion environment. While precipitation rate of Cl－ is one of the factors in residence time of Cl－, residence time of Cl－ on girder is considered to directly affect the corrosion of that of steel bridges. So this study examines the residence time of Cl－ on inside-ward web of the girder of the bridge, based on the precipitation rate of Cl－ on girder and removing rate of Cl－ from web by rinsing with dewdrop. Exposed period of the examined web are 1 month, 3 months, and 1 year. The residence time of Cl－ on inside-ward web exposed during 1 month or 3 months is calculated to be 30 to 700 days. The residence time is long during winter and spring, short during summer and fall. This fluctuation of residence time infers that Cl－ is accumulate during winter and spring, and rinsed during summer and fall. The residence time of Cl－ obtained from web exposed during 1 year is 250 days, suggesting that Cl－ on the inside-ward web is replaced within period of 1 year.