In recent years, extending the service lives of bridges has become a topic of discussion. As the bridges built during the rapid economic growth period have reached the end of their service lives, replacing these bridges or extending their service lives are being discussed. Within this situation, local municipal governments are also conducting regular inspections once every five years as part of preventative maintenance, rather than performing corrective maintenance. In this study, we will shed light on which bridges are most prone to rapid deterioration by using data from the regular inspection of bridges. We will do this by calculating the deterioration rate from inspection data from two inspection cycles in order to determine the environmental factors that affect the deterioration rate. In regards to analysis methods, we used Hayashi’s Quantification Method Type I to grasp the level of influence each factor has on the deterioration rate.

bridge; maintenance; regular inspection; bridge soundness; natural environments