Precise finite element modelling of the bond-slip contact behavior between CFRP composites and concrete

Abstract

Repair or strengthening of concrete structures using carbon fiber reinforced polymer (CFRP) composites dependents on the bond strength between the CFRP sheets and concrete. In this study, the bond-slip behavior and strain distributions between CFRP strips and concrete interface were evaluated. Fifteen concrete blocks externally bonded with CFRP strips were simulated using nonlinear finite element analysis. The main variables were the CFRP strip width, length, and concrete strength (25, 35, and 45 MPa). The CFRP strips were bonded in three lengths (Lf): 120, 200, and 280 mm, and for each Lf, three widths (Wf) were used: 60, 100, and 140 mm. Normal stress, lateral strain, and axial strain distributions were graphed across the CFRP strip as a surface graph. Irregular distributions were observed in the lateral strain and normal stress contours; obvious variation across the width of the CFRP strips was noticed. The axial strain showed regular distribution in the x and z directions. Both the pull-out force and slip increase with increase in Lf, Wf, and concrete strength. However, the influence of Lf was more pronounced than Wf for both ultimate load and slip. Finally, a precise representation of the lateral strain across the CFRP strip contact area was developed. Based on independent block model tested experimentally, the pull-out load-slip behaviors clearly indicate that the proposed model provides more precise and accurate representation than typical modeling without treatment of the end contact regions between the CFRP composites and concrete.