Depending on the seriousness of degradation, a few PC bridges are under reconstruction and its planning. In these tens years, several nondestructive and destructive evaluations have been performed. Then, the degradation and problems such as no-grout-filling, rail-water-invasion, corruption, thinning and disconnection of PC bridges has revealed and been detected. Since PC (Pre-stressed) bridges were first constructed, about 40 years has passed. Moreover, neutron back scattering detection of water in PC sheath is also explained. We have done preliminary experiments on X-ray transmission imaging of PC wires and on-grout-filling in the same height PCs in 450–750 mm thick concretes. This is expected to be an early degradation inspection. Further, we are trying to detect rainwater detection in PC sheath, and asphalt and floor slab by the 3.95 MeV neutron source. Finally, we are going to propose a technical guideline of nondestructive evaluation (NDE) of PC bridges by taking account of both X-ray inspection and structural analysis. By obtaining X-ray transmission images of no-grout-filling in PC sheath and thinning of PC wires, we plan to carry out numerical structural analysis to evaluate the degradation of strength. Now we are to start X-ray transmission inspection for highway PC bridge (box) by using 3.95 MeV X-ray sources in Japan in 2020. T-girder-, Box- and slab- bridges are considered. We have developed portable 950 keV/3.95 MeV X-ray/neutron sources and applied them to inspection of PC concrete thicker than 200 mm within reasonable measuring time of seconds - minutes.
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