Elastic wave simulation in ground anchors for the estimation of pre-stress

Abstract

Application of pre-stress on strand wires inside a structure is a way to reinforce the low tensile strength of concrete and soil materials. After years in service, the strands may lose the pre-stress due to corrosion or other reasons endangering the whole structure. Since there is no accessibility to the strands inside the structure, any inspection should be conducted on the anchor head. In this study, elastic waves on the anchor head are numerically simulated. Parameters like the wave amplitude and propagation time are influenced by the stress of the strand wires which affects the contact between the threaded steel rod, and the surrounding 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. Results are compared with experimental under different levels of pre-stress. Therefore, an easy and fast procedure for non-destructive inspection of the pre-stress load on the strands is discussed.