Monotonic and cyclic behaviour of a stainless steel cuff system for beam-to-column connections between pultruded I-section GFRP profiles

This paper presents an experimental study about the monotonic and cyclic behaviour of beam-to-column connections between pultruded GFRP profiles with I-section, joined by means of stainless steel cuff connection parts. This study pursues a previous investigation by the authors in which custom stainless steel cuff parts were proposed for beam-to-column connections between pultruded tubular GFRP profiles, which presented very satisfactory performance under both monotonic and cyclic loading. A similar concept is now investigated for joining profiles with I-section shapes, which are more often used in civil engineering applications. Four series of full-scale beam-to-column connections were tested under monotonic loading, using stainless steel cuffs of two different plate thicknesses and lengths. The results show that higher cuff thickness and length provided higher initial stiffness and strength, with the cuff thickness being the most influential parameter. Conversely, the ductility of the connections decreased with increasing cuff thickness: the series with thinnest cuff parts presented the highest ductility. The series with the most ductile cuff part was also tested under cyclic loading and presented significant capacity to dissipate energy, but showed marked pinching. These results were compared to those of a stainless steel flange cleated connection system previously tested using the same GFRP I-section profiles: the connections using cuff parts presented worst mechanical behaviour than the cleated connections. This indicates that the cuff connection system is more efficient to join tubular sections than open sections, such as I-sections.