Wedge Anchorage for CFRP Strips

Abstract

For several decades wedge anchorages have been used with great success for the prestressing of steel strands in civil engineering structures. Due to the anisotropy of carbon fiber-reinforced plastics (CFRP) these wedges are not efficient with CFRP tendons. High lateral and shear stress values develop in the CFRP–wedge interface that lead to a premature failure of the CFRP. A comparison of different anchorage methods corroborates the outstanding advantages of wedge anchorages over other anchoring techniques. To benefit from these advantages, a new wedge design is presented that eliminates the high lateral and shear stress values in the CFRP–wedge interface of conventional wedges. Numerical simulations were performed to show the advantageous lateral and shear stress distributions. Tensile tests on 1.2mm thick CFRP strips and a bonded CFRP–wedge interface reached ultimate loads higher than the guaranteed tensile load. The tests on 2.5mm thick CFRP strips were performed with an adhesively bonded wedge–CFRP and a friction only interface. The ultimate loads in the tests were for the adhesively bonded interface 84 and 87% of the guaranteed tensile load, whereas the friction only interface was even able to anchor 93% of the tensile load.