Evaluation for corrosion state of lower gusset plate connections on steel truss bridge

Many existing steel bridges in Japan were built in high economic growth period and the number of bridges over 50 years will increase drastically in the upcoming years. Due to the heavy traffic and severe natural environment, the deterioration and damage will increase rapidly. Improvement of technologies related to inspection, diagnosis, repair, reinforcement and appropriate maintenance is needed. Concerning the steel truss bridges, the serious corrosion damage has been reported recently, especially on the diagonal members and the gusset plate connections. The fracture of these members of steel truss bridge is likely to lead the collapse of the entire truss bridge. In this study, the detailed corrosion shape of the two lower gusset plate connections that were cut from the steel truss bridge were measured by using the laser measurement equipment, and the actual corrosion state of the outside and the narrow inside surfaces of the lower chord members and the gusset plate connections were evaluated on the basis of the corrosion depth distribution of these surfaces. Based on the detailed results of corrosion measurement, the corrosion states and the corrosion characteristics of reinforced and non- reinforced gusset plate connections were clarified.