Azuna TAKAYASU 

A study on prediction method of bridge health criteria and maintenance cost based on the results of inspection and repair

Kiichiro HATOYAMA

�@In this study, in order to understand how much repair costs local governments will need in the future when bridges are deteriorated, I tried to formulate the natural deterioration tendency of bridge health level and to forecast their repair costs.
�@In the bridge inspection, damage and performance of bridges are evaluated by health level index. Since in Niigata prefecture, seven-level health level index is used, I decided to use this index for this study.
�@First, in order to predict the natural tendency of bridge health deterioration, it is necessary to grasp the tendency of bridge health deterioration without any maintenance and repair. In this study I tried to understand by analyzing the age distribution of bridges for each health level for each bridge type. The time lag correlation analysis revealed the standard period of transition between neighboring health levels for each bridge type. However, it is still impossible to know when bridges start their deterioration after construction (initial performance preservation periods). I tried to calculate them by various methods. As a result, I decided to use the bridge age that gives maximum deference between cumulative relative frequency of initial health level and that of all health level. By combining the results of this and the time lag correlation analysis, I obtained the tendency of natural deterioration of bridge health level.
�@To predict repair cost, I decided to use the actual repair data of Niigata City (N = 113) and Nagaoka City (N = 28). In this study, I estimated the repair cost of concrete (BOX, PC, RC) bridges and steal ones separately. As a result, I obtained the estimated repair cost functions that denote the repair cost increase as the bridge health level deteriorates.