Experimental and numerical investigations of seismic performance of hybrid joints with bolted connections

Based on traditional concrete column-steel beam hybrid structures, this paper ventures to propose three new hybrid joints with bolted connections by moving the plastic-hinge from the end of a beam to a weakened point, according to the idea of weakening the extension beam end-joint of a steel structure. Cyclic loading tests of three beam-column specimens are conducted to evaluate the new joints. The failure mode and mechanism, bearing capacity, ductility and energy dissipation are obtained. The experimental results indicate that adverse effects on the joint core can be avoided by moving the plastic hinge outside the joint to the weakened connection. For the novel type of a steel jacket with no stirrups implemented in the joint core that is presented in this paper, higher bearing capacity and acceptable energy-dissipation performance are achieved. Z-shaped hysteretic curves reveal the large slip of the joint with the cover plates. The “bow” shape hysteretic curves of end-plate semi-rigid joints exhibit satisfactory seismic performance as energy is dissipated through the bending deformation of end plates. The friction copper plates that are added inside the cover plates can enhance the energy dissipation ability. With reasonable design, the damage can be concentrated in the weakened connection and the damaged components can be conveniently repaired and replaced after an earthquake. The modeling method in the open source software OpenSEES is proposed, and the feasibility of the method is verified by comparing with the experimental data.