Structural health monitoring of the reinforced concrete plug joint system for existing concrete bridges

The use of deicing salts in heavy snowfall area in Japan has been increased since the 1990s. The purpose of using deicing salts is to ensure the road safety during the winter season. However, as a trade-off, the highway bridges are deteriorated by salt attack due to the deicing salts. Thus, this study examines the number of water leakage from bridge joints in the Hokuriku Expressway in Japan. This survey was conducted to investigate the relationship between deteriorations at the girder ends due to the salt attack by deicing salts and the water leakage from the bridge expansion joints. It is found out that the water dissolved with salts from deicing salts has accelerated the damage of the reinforced concrete (hereafter RC) structures at the girder ends. Therefore, as a preventive measure, a new highly durable jointless system named RC plug joint system (hereafter RC plug joint) for existing concrete bridges are being proposed. The RC plug joint connects the girder end to the abutment's backwall using anchor reinforcing steel bars (hereafter rebars) and fiber reinforced concrete. The analysis of live load influence, a temperature change and the seismic influences using a finite element analysis are conducted. The experiment model in the case of huge earthquake occurrence had already grasped the destruction form of the RC plug joint. From this analysis, it is recommended that the RC plug joint should be applied to an existing concrete bridge with the bridge lengths less than 40 meters. In addition, to monitor the structural health of the RC plug joint, assessment of 85 locations of installed RC plug joint confirm the modeling analysis results. As a result, the RC plug joint can prevent water leakage and allow for a smooth ride of vehicles at the joint. In conclusion, RC plug joint is proposed as a method that can improve the durability of existing concrete bridges.