Pre-stress evaluation for steel strand based on energy leakage ratio of ultrasonic guided wave

Abstract

Accurate prediction of the effective pre-stress in steel strands is of great importance for service performance assessment in pre-stressed structures. In this study, a new parameter for characterizing the pre-stress in steel strand is proposed, named energy leakage ratio (αEL) of ultrasonic guided wave (UGW). Firstly, the propagation of UGW between wires of the strand was theoretically analyzed. Then, finite element (FE) models of steel strand were established and laboratory experiments were conducted to verify the effectiveness and accuracy of the proposed αEL-based pre-stress evaluation approach. Results show that αEL increases linearly with inter-wire contact width. αEL can be taken as a new parameter for strand pre-stress identification, it shows a high linear correlation with pre-stress level, no matter whether the excitation position is located in core or helical wire. In terms of numerical and experimental results, the αEL-based pre-stress evaluation errors are within 3% and 4% respectively. Compared with the acoustoelastic effect based and nonlinear ultrasonic based approaches, the αEL-based approach showed the advantage in pre-stress identification accuracy.