Experimental investigation on the mechanical properties of a bond-type anchor for carbon fiber reinforced polymer tendons

Carbon fiber reinforced polymer (CFRP) has gained popularity in civil engineering applications due to its high tensile strength, light weight, corrosion resistance, and fatigue resistance. However, the anchorage of CFRP tendons has been a challenge due to the relative low transverse shear strength of CFRP. To study the mechanical properties of bond-type anchor for CFRP tendons, straight-type, inner-cone-type, and composite-type anchors were developed in this study. The bond-slip behavior of CFRP tendons inside anchors and multiaxial stresses of the steel sleeve were experimentally tested. The effects of anchor type and length on the anchorage performance of CFRP tendons were studied with the focus on the anchoring mechanism. Test results demonstrate that the composite-type anchor exhibits the most reliable load-transfer mode and can eliminate the notch effect occurred in the inner-cone-type anchor. The peak bond stress initially occurs at the loading end of the anchor and gradually moves to the free end of the anchor as the load increases. This is related to the gradual failure of chemical adhesive between the CFRP tendon and the colloid. Besides, bond-slip relationship of CFRP tendon inside anchor is nonlinear. The slippages of CFRP tendons are initially small but increase quickly with increasing load. When approaching failure, the slippages increased significantly. In addition, the slippage of the anchor with scattered-end tendon is smaller than that with non-scattered-end tendon, indicating that the anchor with scattered-end tendon has superior bonding property.