Finite element study of plate-end stresses on near-surface mounted FRP strips

 ABSTRACT

Two sets of simply supported reinforced concrete beams strengthened with nearsurface mounted CFRP strips were modeled in 3D using the finite element analysis software ANSYS, with the aim of studying the stress distribution near the strips’ cut-off points. The geometry and material properties of the beams were modeled accurately, allowing for the nonlinear behavior of concrete, steel reinforcement and epoxy adhesive, and using a refined mesh at the strip ends to improve accuracy locally. After establishing reasonable accuracy of the finite element analyses through comparison with experimental results, the concrete stresses at the concrete- adhesive interface along the strip’s length were studied at increasing load levels up to failure. It was observed that the concrete adjacent to the adhesive layer is subject to longitudinal and transverse shear stresses as well as stress normal to the strip face throughout the entire load history. Although the distribution is highly variable along the strip length after cracking, overall tendencies of the stress distributions are discernible. Hence, it is concluded that these orthogonal stresses must be considered in the plate-end debonding mechanism, and therefore, the currently available analytical models to predict this type of debonding in near-surface mounted strips are not in agreement with the behavior observed through 3D finite element analysis and published experimental data.