Mechanical behaviour of steel timber composite shear connections

This paper presents an experimental investigation on a Steel Timber Composite (STC) connection system composed of steel H-section and engineered timber, glulam produced from Larix gmelinii. Static push-out tests were conducted on this new composite connection type to investigate its yield characteristics as well as relevant failure modes. Effects of the type, diameter and spacing of shear connectors, and thickness of glulam on the mechanical response of this STC connection were carefully analysed. For all considered specimens, “two-hinge” yield mode was observed but the failure of joints were characterized by the simultaneous occurrence of embedding strength failure of glulam flanges and bending failure of bolts used as shear connectors. The ultimate load carrying capacities as well as yielding of joints were directly proportional to the bolt diameter but inversely proportional to bolt spacing. As the thickness of glulam was increased, both the ultimate load and the yield load of joints initially increased but then decreased. Self-drilling screw connected joints performed better than the bolt connected joints both in terms of stiffness and ductility. Experimentally obtained key design parameters were compared against those predicted using GB/T 50005–2017, NDS-2018 and Eurocode 5. It is worth noting that the code predictions are not suitable for design application due to significant conservatism or over-prediction of connection response; this shows a clear gap in the existing knowledge on STC connections. Foschi formula was used to predict the nonlinear load-slip behaviour of considered specimens and analytical predictions showed reasonable agreement with test results.