Performance of anchorage assemblies for CFRP cables under fatigue loads

This paper investigates the fatigue performance of CFRP (carbon fiber-reinforced polymer) cables using a bond extrusion anchorage system in which the variable stiffness of the bonding medium in the steel sleeve is adopted. A group of cyclic loading experiments under a maximum stress of 0.45fu and a stress range from 500 MPa to 900 MPa were carried out to determine the fatigue damage evolution of the cable anchorage assemblies. In addition, the fatigue failure mechanism and the influence of cyclic loading on the mechanical performance, such as the stress and stiffness of the cable, the relative displacement of the anchorage assemblies and the stress of the steel sleeve, were also investigated. The results indicated that the stress range primarily affected the fatigue life of the cable anchorage assemblies. The damage of the anchorage assemblies was generated in the cable at the outer layer tendons, which first forms longitudinal cracks, then splits and finally results in rupture. The axial strain of the cable was still linear, and the axial stiffness decreased by 8% compared with the initial stiffness after 1.2 million cycles under a stress range of 500 MPa. The stress variation in the steel sleeve was not obvious with cyclic loading. The fatigue performance for the anchorage assemblies was obtained and it could realize 2 million cycles below the design stress range of 470 MPa based on the trend analysis from the fatigue experiment.