New Concrete Anchors for Carbon Fiber-Reinforced Polymer Post-Tensioning Tendons—Part 1: State-of-the-Art Review/Design

In posttensioning applications, carbon fiber-reinforced polymer (CFRP) tendons tend to fail prematurely when used with anchors developed for steel tendons. A new non-metallic anchor for CFRP posttensioning tendons was developed to overcome the problem of premature failure and to provide a completely metal-free posttensioning system. The new anchors, as with conventional steel anchors, hold the tendons through mechanical gripping but without the corrugations between wedges and tendons. Each anchor consists of an outer barrel with a conical bore and 4 wedges. The anchor components are made of ultra-high-performance concrete (UHPC) developed specifically for this anchor, and the barrel is wrapped with CFRP sheets to provide the confinement necessary to fully utilize the strength and toughness of UHPC. The new concrete has compressive strength in excess of 200 MPa together with excellent durability and fracture toughness. Three mm chopped carbon fibers were incorporated into the UHPC to enhance fracture toughness. A review of the state-of-the-art of anchors for prestressing FRP tendons is introduced, followed by design of the new concrete anchors for posttensioned CFRP tendons.