FRP strengthened SHS beam-column connection under monotonic and large-deformation cyclic loading

Abstract Many civil applications use square hollow sections (SHSs) as members in beam-column connections which can be vulnerable under cyclic loading. Cyclic loadings from earthquakes, wind, waves and currents affect onshore and offshore civil infrastructure. In addition, these beam-column connections can become structurally inadequate through incremental service loads, design/fabrication errors and material property degradation over time. Due to this, it will be necessary to strengthen SHS beam-column connections to improve their performance under sustained monotonic and cyclic loadings. This paper treats the performance of SHS beam-column connections strengthened with externally bonded carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). Experimental investigations have been conducted on the bare, CFRP and GFRP strengthened SHS connections under monotonic and cyclic loading. Results show that under cyclic loading, both CFRP and GFRP strengthened SHS beam-column connections exhibit improved ultimate moment capacity, moment degradation behaviour, secant stiffness, energy dissipation capacity and plastic hinge behaviour compared to their bare counterparts. Under monotonic loading, both types of strengthened connections show higher moment capacity, secant stiffness and ductility. In addition, CFRP strengthening enhances the ultimate strength, while GFRP strengthening enhances the ductility.