Experimental and Numerical Evaluation of Unbonded Posttensioning Tendons Subjected to Wire Breaks

AbstractThe development of corrosion as a result of tendon exposure to moisture or corrosive media often leads to wire fractures. Such fractures in unbonded tendons are expected to induce global strand and anchor response through the progression of prestress loss from the break to the end anchors. Radial pressure, interwire friction, and lateral confinement, however, affect the magnitude of prestress loss carried to the anchors and have important implications on breakage detectability by tendon monitoring methods that rely on anchor response. This paper presents an experimental investigation of tendon behavior after successive wire cuts in confined and unconfined conditions and demonstrates the effects of confinement on stress recovery. In addition to analysis of strand prestress loss and axial strain along individual wires, the strand’s dynamic postbreakage response was examined. Moreover, the effects of deviators on stress recovery were tested with a multistrand tendon specimen. A finite-element model of a seven-wire strand was developed and experimentally validated. Both experimental and numerical results showed significant prestress loss even at distant locations from wire breaks and confirm a correlation between wire breakage and modal properties, which can be a useful damage indicator.