Japan's railways began operations about 140 years ago. The majority of its steel railway bridges now have 50 years or more of service.
It is therefore expected that the number of steel bridges requiring repair, reinforcement or replacement will increase in the future. Consequently, the Railway Technical Research Institute is proposing a method to extend the life and strengthen the earthquake resistance of deteriorated steel-girder and abutment-type bridges without replacing steel girders, by integrating the following structures:
(1) Abutments and backfills with reinforced concrete (RC) walls that are connected to each other rigidly with nail-reinforced soil;
(2) Connecting steel girders and abutments with reinforced concrete;
These are measures which improve the function of steel girders, abutments and backfills in normal service periods and during earthquakes. Bridges reinforced with this type of structure are called "Integral Bridges with Nail-Reinforced Soil (NRS-Integral Bridges)."