2025 Volume 4 Issue 1 Pages 387-396
A case of rupture and protrusion of a transverse post-tensioning PC steel tie bar occurred on a PC beamslab bridge in Ehime Prefecture. It was necessary to detect the rupture regardless of the presence or absence of protrusion. A full inspection was conducted by close visual inspection, hammering-sound inspection, and transmission ultrasonic testing. Ultrasonic wave incident from the end of a steel tie bar were detected by a sensor at the other end of the bar even when the bar was clearly broken and separated, although the amplitude of the waves was reduced. A mechanism in which ultrasonic waves propagating through the steel bar bypass the surrounding concrete at the fracture and re-enter the steel bar was assumed. Experiments were conducted using a small steel-bar concrete beam model to confirm this bypassing-mechanism. Even if the steel bar was separated, transmitted ultrasonic waves could be detected at the other end. Numerical analysis on the steel-bar concrete beam model was conducted to verify the wave bypassing mechanism and eventually to demonstrate the feasibility of a transmission ultrasonic test method for detecting the rupture of transverse post-tensioning steel tie bars.
