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Keynote Speech

In Japan, a lot of social infrastructures like bridges, tunnels, port and harbor facilities and so on were built in 60’s to 70’s, which was the period of rapid economic growth in Japan. Since 40 to 50 years already passed after their constructions, there is serious concern over the deterioration in quality or performance of many infrastructures in near future in Japan. According to the white paper issued by the Japanese government, for example, the number of road bridges over 50 years old existing in Japan will increase from 8% in 2010 to 53 % in 2030.

To solve the aging problem of infrastructures, a strategic action plan is required for preventive maintenance of structures, which includes inspections and monitoring as well as the evaluation of structures, and technologies for repair, reinforcement and renovation. It is clearly noted that nondestructive testing and evaluation plays an important role as a key technology at the first step in the strategic plan.

Among various nondestructive testing methods, some on-going researches on ultrasonic waves and vibrations applied mainly to concrete materials are introduced. Topics may include the SAFT imaging of defects in concrete using ultrasonic phased array method, the detection of adhesive resin debonding between a steel plate and concrete by means of laser technology, the evaluation of damage in concrete by nonlinear ultrasonic waves, and the application of air-coupled transducers to detect defects in concrete.