The Use of Hashin Damage Criteria, CFRP–Concrete Interface and Concrete Damage Plasticity Models in 3D Finite Element Modeling of Retrofitted Reinforced Concrete Beams with CFRP Sheets

The properties of reinforced concrete beams strengthened using carbon fiber-reinforced plastic (CFRP) sheets have been thoroughly studied, establishing a firm knowledge of analysis and design procedures. Snapping of CFRP sheets during loading is a typical failure mode in such strengthened structures. Applying epoxy resin to bond CFRP sheets to the reinforced concrete beam creates a new composite material. This paper presents the effect of damage initiation criterion in the composite CFRP material as well as the interface behavior on the performance of CFRP-strengthened reinforced concrete beams. Hashin damage in the CFRP sheets, cohesive behavior in the interface material, and concrete damage plasticity models are used to simulate typical snap patterns of composite CFRP material, capturing interaction between CFRP debonding, concrete cracking, and failure mechanisms. A parametric study is conducted to investigate the effects of the undamaged response of the CFRP material and damage initiation criterion in terms of tensile strength, compressive strength, and shear strength in the axial and transverse directions. Finite element model results are found to be in close agreement with flexural beam test results in terms of both strain and deflection. It is concluded that Hashin damage properties are the main parameters influencing snapping failure mode. This study may serve as a valuable reference to aid in understanding the behavior of retrofitting with CFRP–epoxy composite material in a bridge or building models.