Analysis of the bond between near-surface mounted CFRP laminate strips and concrete

Abstract

The flexural and the shear resistance of concrete, masonry and timber structures can be efficiently increased using near-surface mounted (NSM) CFRP laminate strips. This technique consists on introducing CFRP laminate strips into grooves made on the cover concrete of the structural elements to be strengthened. Bond behavior of CFRP reinforcement is a key feature, not only for the strengthening efficacy provided by this technique, but also in the structural design. To assess the local bond stress-slip relationship, a numerical strategy was developed taking into account the results obtained in monotonic and cyclic pullout-bending tests that were carried out for this purpose. This relationship was transformed into a bond stress-slip constitutive law for a line interface finite element, used to simulate the concrete-CFRP bond behavior. Important design aspects, like the anchorage length of the CFRP to accomplish the requisites imposed by service and ultimate limit state analysis, can also be determined by the developed model. The experimental and the numerical research are described in this paper.