Interfacial stress analysis of RC beams strengthened with hybrid CFS and GFS

The mechanical performances of the interface between the concrete and the fiber reinforced polymer (FRP) are investigated using nonlinear finite element method (FEM) in this paper. The paper focuses on simulating the entire debonding process of the FRP sheets. The interfacial stress levels between the carbon fiber sheet and the glass fiber sheet (CFS–GFS) as well as that between CFS and CFS are compared. A parametrical study was carried out to show how the mechanical performances have been influenced by the load, the elastic modulus, the thickness of adhesive layer and the width of FRP sheets. The simulation results show that the interfacial stresses at the ends of the beam increase with the load and the elastic modulus, but decrease with the thickness of the adhesive layer. The interfacial stresses almost do not vary with the width of FRP. The numerical results of the interfacial stresses have good agreement with analytical results. The numerical results show that it is an effective method for CFS–GFS hybrid fiber sheets to strengthen concrete structures. Hybrid fiber sheets can efficiently reduce interfacial shear stresses of FRP sheets and meanwhile prevent interfacial normal stresses from reaching a high stress level. The results of this numerical study are beneficial to understand the mechanical behaviour of the material interface and design the hybrid FRP reinforced concrete structures.