Experimental, analytical and numerical study of hybrid timber-steel connections with steel fuses

The structural behaviour of eight full scale hybrid glued laminated timber (GLT) beam to steel column connections with glued-in high strength (8.8 grade) steel rods, and replaceable mild (4.6 grade) steel fuses were investigated by static and cyclic laboratory testing of T-shape beam-to-column subassemblies. Apart from the peak load, stiffness, failure mode, ductility and energy dissipation capacity, the stiffness and strength degradation of the hybrid connections were evaluated by replacing the mild steel fuses and testing some of the subassemblies up to six times. The test results demonstrated the potential of bonded-in high strength steel rods with mechanical couplers to develop hybrid connections that can be easily dismantled and replaced. The strength and stiffness degradation of the connections observed after six loading repeats was 18.3 % and 33.5 %, respectively. Simple mechanistic models are proposed to estimate the short-term service stiffness and ultimate bending moment capacity of the hybrid connections with replaceable mild steel fuses. Nonlinear 3D finite element simulation was used to conduct parametric studies and to provide insights into the effects of bolt pre-tensioning and fuse grade.