Behavior of fiber-reinforced polymer-reinforced anchorage zones for post-tensioned, concrete structures

Due to their corrosion resistance and strength-to-weight ratio, fiber-reinforced polymer (FRP) Materials have been suggested as an alternative to steel to be used in structural concrete. The relatively low stiffness of FRP compared with steel, implies that concrete structures containing FRP; ought to be prestressed. In this way, the serviceability of the structure is improved, and higher ultimate strength is attained Much research into FRP-prestressed concrete has now been conducted, but the design of FRP-reinforced post-tensioned anchorage zones (where the tendon force is transferred to the concrete) has received very little attention. The current research concentrates on investigating the, feasibility of using aramid FRP (AFRP) helical reinforcement in local anchorage zones for wholly non-metallic, efficient post-tensioned concrete structures. A total of 47 patch-loaded concrete specimens (of circular and rectangular cross section) have been tested and relevant results are provided herein. Laboratory-made AFRP has been used as reinforcement in a circular helical form. Test results are compared with predictions based on an existing design approach that has been modified for the case of FRP reinforcement. It is shown that the relative diametrical dimension between the reinforcing helix and the bearing plate is a critical factor, influencing the post-elastic behavior Further, by combining helical and mat reinforcing systems, both higher ultimate capacity and real ductility of the anchorage zones are achieved.