GFRP hollow column to built-up beam adhesive connection: Mechanical behaviour under quasi-static, cyclic and fatigue loading

A new adhesive beam-column connection is tested which possess the highest strength and stiffness compared to any other similar adhesive or bolted connection tested in the past. A square GFRP hollow section, acting as a column, was connected to a built-up beam made of two GFRP U-profiles by means of either epoxy or steel bolts. The beam-column assembly formed an L-shaped frame which was tested by applying a point load at the beam free end while the column was fixed at its base. Five bolted and five adhesive replicate connections were subjected to quasi-static loading up to failure. Another three adhesive connections were subjected to 400, 800 or 1200 cycles of loading and unloading with the maximum load being equal to 0.50 P_u,avg, where P_u,avg is the average static strength of the replicate adhesive specimens. At the end of the cyclic loading, the latter specimens were loaded quasi-statically to failure. Finally, another two adhesive connections were subjected to fatigue type loading. They were successively subjected to at least 196 cycles of loading and unloading with the load amplitude being 0.50 P_u,avg in the first 60 cycles, 0.75 P_u,avg in the next 60 cycles, 0.85 P_u,avg in the following 60 cycles and 0.95 P_u,avg after the 180th cycle. The test results show that the proposed adhesive connection can achieve on average 82% higher strength and 380% higher rotational stiffness than the companion bolted connection. Furthermore, the above cyclic loading has negligible effect on either the strength or the stiffness of the connection. Finally, the connection can sustain the foregoing fatigue load up to almost 180 cycles without significant damage but it will not be able to withstand the full 60 cycles of the load with 0.95 P_u,avg amplitude. The current results demonstrate the superior strength and stiffness of the new adhesive connection compared to a similar bolted connection.