NOVEL METHOD FOR FINDING THE INTERFACIAL SHEAR STRESS BETWEEN FRP-CONCRETE INTERFACE

Abstract

Fiber Reinforced Polymer (FRP) materials have gained significant attention in the construction industry due to their high strength, durability, and corrosion resistance properties. One critical aspect in the design and analysis of FRP-restrengthened structures is the evaluation of shear stress at the interface between FRP and concrete. Accurate determination of this shear stress is essential for ensuring the structural integrity and performance of FRP-strengthened elements. Traditional methods for evaluating interfacial shear stress have limitations for accurately capturing the complex interactions between FRP and concrete. This research proposes a novel method for calculating shear stress at the FRP-concrete interface, taking into account the simplicity of the specimen, test apparatus and accuracy. For the study, three different cylindrical specimens, of size 100 mm and height 273.2 mm were cast to calculate the interfacial shear stress between FRP and concrete. The FRP sheet was applied in an inclined plane, making an angle of 30° with the vertical face of the cylinder. In this research, experimental investigations were conducted to gather data on the bond behavior of FRP-concrete interfaces using a UTM machine. Emphasis is focus on understanding the influence of parameters such as surface preparation, adhesive properties, and specimen size on interfacial shear stress. The proposed method offers a comprehensive approach to assess shear stress at the FRP-concrete interface, considering the complex interactions between materials and loading conditions. By incorporating simple experimental arrangement, this research provides a valuable tool for designing and analyzing FRP-strengthened structures with improved accuracy and reliability. Moreover, an analytical study was also performed to evaluate the effect of the FRP sheet on the flexural capacity of the beam. The FRP sheet was applied to the soffit of the beam for the study and the last study was done to numerically investigate the effect of varying thickness of FRP and Epoxy in an inclined plane of the cylindrical sample. The experimental study revealed that the bond strength between the FRP and the concrete element was determined to be 4.67 MPa. This finding was obtained through a series of controlled tests designed to measure the adhesion between the FRP material and the concrete substrate. The measured bond strength of 4.67 MPa indicates a robust interaction between the two materials, which is critical for the effectiveness of FRP v reinforcement in structural applications. These results provide important insights for the design and implementation of FRP systems in enhancing the durability and performance of concrete structures. The analytical investigation into the effect of the FRP sheet on the flexural capacity of the beam revealed that by applying a 4.04 mm thick FRP sheet, the flexural capacity of the beam increased by 8.60%. The 4.04 mm FRP sheet, strategically bonded to the soffit of the beam, provided additional tensile reinforcement, effectively enhancing its load-bearing capacity. The 8.60% increase in flexural capacity signifies a substantial improvement, demonstrating the effectiveness of FRP sheets in strengthening concrete beams and extending their service life. The numerical investigation conducted to study the effect of varying thicknesses of FRP sheets and epoxy on bond stress revealed that by applying a thicker layer of epoxy on the inclined plane in a cylindrical sample significantly increases the shear capacity of the interface. By varying the thickness of the epoxy layer, the study was able to analyse its impact on the bond stress and overall shear capacity of the interface. The results indicated that a thicker epoxy layer enhances the adhesion between the FRP and concrete, thereby improving the interface's resistance to shear forces.