การประชุมวิชาการระดับชาติ ครั้งที่ 16
มหาวิทยาลัยราชภัฏนครปฐม

            In the past 60 years, bridges have been built to create networks and accommodate increasing traffic volumes. Steel is one of the most commonly used materials in bridge construction due to its good tensile strength and quick construction time. However, steel bridges are susceptible to deterioration from environmental factors, higher traffic load, and traffic volume. Reinforcing steel structures with carbon fiber-reinforced polymer (CFRP) has become an exciting technology. CFRP material is lightweight and can withstand severe environments and corrosion well. Typically, epoxy adhesive is used to bond the CFRP material to steel structures during the CFRP installation. Therefore, the effectiveness of the reinforcing system depends on the bonding strength in the epoxy layer at the interface between the materials. This paper focuses on the effects of the size and location of clamping forces applied on CFRP material on the bond strength and tensile behavior of steel plates strengthened with CFRP. The bolt connection is used with the epoxy adhesive to form a hybrid bonded joint. The tensile test of thirteen double-strap joint specimens with one CFRP strengthening layer and various clamping forces and locations was carried out. The specimens were clamped by applying various torque levels, i.e., 0, 20, 40, 60, and 80 N-m, at the bolt connections. Three different patterns of bolt connection positions were investigated, including the positions at the effective bond length (Le), 0.5Le, and 1.5Le. The experimental results showed that an increase in the clamping force increased the bonding strength of the epoxy layer and the tensile strength of the reinforcement system. However, when the bolt torque value reached a certain point, the strength in the epoxy layer did not increase any further, even if the torque value increased. The bolt connection position also affected the tensile strength of the reinforcement system. The strength effectively increased with the number of bolt connections, particularly for the locations within the effective bond length of the strengthening system.