Monotonic and cyclic behaviour of cuff beam-to-column connection system for tubular pultruded GFRP profiles

The use of glass-fibre reinforced polymer (GFRP) cuff parts to join GFRP beams and columns has been object of several experimental and numerical studies in the past, which showed their improved mechanical performance when compared to connection systems that mimic steel structures, such as connections with GFRP web and/or flange cleats. The main objective of the study presented in this paper is to propose and assess a connection system – for tubular GFRP profiles –with similar cuff geometry, but made of stainless steel, in order to achieve higher ductility due to its inherent strain hardening, while maintaining the non-corrodibility capabilities of GFRP. Full-scale tests were performed on four different beam-to-column connection series using stainless steel cuffs with varying geometry and plate thickness. The experimental campaign comprised: (i)monotonic tests for all series; and (ii)cyclic tests for the series with the best performance in the monotonic tests. The monotonic response of the different series varied considerably. As expected, by increasing the plate thickness of the cuff, the initial stiffness and strength of the connections were substantially improved; on the other hand, the moment vs. rotation behaviour of connections with thinner cuff parts was more markedly non-linear and GFRP damage was delayed. Nevertheless, all connection series presented significant ductility, successfully making use of the stainless steel mechanical properties. For both monotonic and cyclic loading, the cuff connection system presented herein provided better mechanical performance than stainless steel sleeve connections developed earlier by the authors, namely regarding initial stiffness, overall strength and energy dissipation.