Experimental study on wedge-bonded anchors for CFRP tendons under cyclic loading

Abstract

This paper is concerned with an experimental study on a wedge-bonded anchor for carbon fibre reinforced polymer (CFRP) tendons under cyclic loading. The adhesive reinforced by quartz sand was tested to be superior as a bonding material for the anchor when compared to the adhesive reinforced by ferrous powder or aluminate powder. Structural responses of the wedge-bonded anchor under cyclic loading were analyzed with regard to system slip, sleeve strain, temperature rise in the anchor zone and residual tensile load capacity. The results indicate that the maximum stress level and stress ratio influence significantly the fatigue performance of wedge-bonded anchors. A cyclic loading with a high stress ratio and low stress level is beneficial due to the synergetic effect of the components in the wedge-bonded anchors. However, enhancing the stress level or lowering the stress ratio leads to a larger slip, greater damage and more loading cycles are needed for the stabilization of wedge-bonded anchors. When the stress ratio exceeds 0.4 and the maximum stress is less than 0.5, damage in anchor zone is initiated and developed in the early stage of cyclic loading, but the anchor becomes stable finally. A large decrease in stress ratio may result in a continuous development of microstructural damage and the eventual failure of the anchor, accompanied by continuously increasing energy dissipation under cyclic loading. The axial strain of sleeve in a wedge-bonded anchor is influenced by the extent of damage evolution and the synergetic effect of anchor assemblies; thereby resulting in different trends in sleeve strain-cycle curves under different stress ratios and stress levels. The temperature rise may be pronounced at a loading frequency of 10 Hz or less, which is related to the stress ratio. The damage development in the wedge-bonded anchor with an infinite fatigue life was analyzed. The mechanism of fatigue damage in wedge-bonded anchors is different from that of adhesively bonded anchors. Moreover, wedge-bonded anchors have a stronger resistance against fatigue due to the interaction between the wedges and the other assemblies.