Shear and peeling stresses at the cut off end of concrete beams strengthened with CFRP plates

摘要

Delamination of FRP to concrete is of tremendous importance if the strengthen structure should be possible to use in a safe manner up to the design load. Two delamination failures can be discern, anchorage- and peeling failure. The first failure is often described as a failure that arises at a crack between the loading point and the end of the laminate. The second failure arises at the end, or near to the end of the laminate, e.g. end peeling failure. This paper present test performed on concrete beams strengthened for flexure using CFRP materials. In these tests, the effect of different elastic modulus in the CFRP plate has been investigated together with its effect on the peeling stresses in the bond zone close to the short end of the plate. Analytical and numerical calculations for the shear stresses at the cut-off end of the CFRP plate have also been made. A comparison between laboratory tests and theory show that the theory is in agreement with the tests. The tests also show that increasing the stiffness of the laminate plate will have a direct influence on the deformations of the beam and the width of the flexural cracks. Furthermore, the distance from the support to the plate end, the Young modulus of the plate and the adhesive properties as well as its thickness has all a large influence on the shear stress.