Investigation of efficient anchorage systems for shear and torsion retrofitting of box girder bridges

Carbon Fibre reinforced Polymers (CFRP) have become an effective solution to upgrade and strengthen existing box girder bridges in flexure, shear and torsion. The introduction of CFRP strain limitations to prevent premature delamination together with the increasing strengthening demands and the necessity for use of fibres of increasing stiffness and thickness has resulted in a very poor CFRP material utilization levels achieved in practice. An effective method to increase CFRP material utilization is by appropriately anchoring the ends of the CFRP. In this paper, a study into CFRP end anchorage solutions is presented which formed the basis of the experimental program. Both uni-directional and bi-directional fabric was applied to the ends of CFRP laminates and tested under direct shear loading. Uni-directional fabric was oriented both horizontally across and parallel to the direction of the laminate. In all cases it was found that the anchorages solutions tested resulted in a distribution of fibre-to-adhesive bond stresses over a greater length, width of concrete and could potentially result full CFRP utilization and laminate rupture.