Discussion about phased array ultrasonic testing technology for high-strength bolts of in-service bridges
High strength bolts are widely used in the connection of steel structure bridges.They usually need to withstand complex stress and the influence of temperature variation in service process,which can cause fracture or failure of bolts.The failure fracture is an important factor to cause the structural integrity failure,so the safety is paid more and more atten-tion.How to detect fatigue cracks in bolts without dismantling them is always a challenge.In this study,the stress analysis on the high-strength bolts of in-service bridge steel towers was conducted.The main positions with high stress level were identified.Through simulation technology,the key technologies of phased array ultrasonic ring array probe line scanning and phased array ultrasonic line array probe fan scanning for detecting bridge bolts were studied.The inspection process and plan for high-strength bolts of in-service bridges were established.The sensitivity and coverage were confirmed using dedicated test blocks,which were tested and verified in the laboratory and the field.By combining with theoretical analy-sis,the full coverage of in-service bridge bolt testing had been achieved,solving the problem of high-strength bolt testing for in-service bridges.
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