In Japan, bridges constructed during the strong economic growth era are facing an aging problem and advanced maintenance methods have become strongly required recently. To meet this demand, we develop the on-site inspection system using 950 keV/3.95 MeV X-band (9.3 GHz) linac X-ray sources. These systems can visualize in seconds the inner states of bridges, including cracks of concrete, location and state of tendons (wires) and other imperfections. On detecting corrosion of tendons, it was confirmed that our linac system has sufficient inspection accuracy. At the on-site inspections, 950 keV linac exhibited sufficient performance and visualized the inner state of concrete bridge. Structural analysis was also performed to evaluate the bearing capacity of the bridge using finite element method.

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