An Innovative Hybrid Connection for FRP Frame Structures: The Role of Column Length

In Fibre Reinforced Polymer (FRP) frame structures, the joints are significantly weaker than the connected beams and columns, compromising structural integrity and leading to inefficient utilization of the connected components. Traditional joining techniques present various challenges, such as disruption of fiber continuity due to holes in the adhesive bond and limited load-bearing capacity due to bearing failure in bolted joints. Additionally, issues like brittle failure and non-repairability further complicate these connections. As a result, hybrid joints are being developed as a solution. These joints combine fibre-reinforced materials and ductile materials, bonded and bolted together. These considerations prompted a research initiative focused on developing an innovative hybrid (steel/FRP) beam-column connection for FRP elements. This novel type of joint was recently patented, and its effectiveness was demonstrated through experimental tests conducted at the University of Salerno. The FRP elements are adhesively bonded to the steel components, while the steel elements are bolted together. All components are designed to be weaker than the bond strength to ensure a ductile response and prevent bond failure. Damage is concentrated in a specific steel element, which can be easily replaced, confirming the repairability of the assembly. In this paper, the experimental results are first compared with those obtained from FEM modelling, and then the study is extended to explore the influence of the column and its connection on the overall mechanical behaviour of the joint.