Estimation of pre-stress in tendons using elastic wave propagation in the anchor head

Abstract

Application of pre-stress on a structure is a way to reinforce materials with low tensile strength like concrete and soil against tensile overload. After years in service, the strands may lose the pre-stress due to corrosion or other reasons endangering the whole structure. Since the strands inside the structure are not easily accessible, any inspection should be conducted on the anchor head. In this study, elastic waves are numerically applied on the anchor head. Parameters like the wave amplitude, propagation time, frequency content and others are influenced by the stress of the strand wires which affects the contact between the steel strand, and the surrounding bolt of the anchor head influencing the acoustic impedance mis-match on the interfaces. The change of contact pressure between the strands and anchor head is simulated by modifying the rigidity of a model interphase material. Therefore, an easy and fast procedure for non destructive inspection of the pre-stress load on the strands is discussed. © RILEM 2013.