Flexural and shear behaviour of adhesive connections for large scale GFRP frames: influence of the bonded area and hygro-thermal aging

This paper studies the influence of several parameters, such as the extension of the bonded area, the load condition and hygro-thermal aging on the global mechanical response of beam-to-column adhesive joints. The experimental program involved the realization and laboratory testing of twenty-seven full scale glass fiber reinforced polymer (GFRP) connections composed of a square hollow section, acting as a column, connected to a built-up beam made of two U-profiles by means of the epoxy resin. The beam-column assembly formed an L-shaped frame tested by applying a point load at the beam free end (bending) and close to the column (shear), while the column was fixed at its base. Furthermore, five different bonded area configurations were considered and tested, with two different aging conditions being taken into account: conditioning in Tap Water and Sea Water for one year at the constant temperature of 30°C. The results show that the variation of the bonded area extension influenced the strength but not the stiffness of the connections under investigation, while the hygro-thermal conditioning influenced both of them, with it affecting stiffness more than strength. Finally, the bending load condition (torsion for the resin) was selected as the worst load condition for the joint inducing shear stress levels in the adhesive layer incompatible with its strength limit.