Load–slip behavior of steel bearing–square reinforced concrete column connection joints with adhesive bonding and self-locking

The connection joint between a steel beam and a reinforced concrete (RC) column is crucial for strengthening and renovating the existing buildings; hence, designing simple, safe, and reliable connection joints is necessary. This study proposed a novel steel bearing–square RC column connection joint with adhesive bonding and self-locking and investigated seven half-scale connection joints with variable joint configurations under vertical loads. The typical failure modes, load–slip behavior, interfacial shear stress, and slip stiffness were analyzed through a parametric study of the taper angle of the square tube, the height of the steel bearing (i.e. contact area between the tube and the concrete), the structural adhesive, and the type of steel bearing surrounding the RC column. The results demonstrated that for a steel bearing–square RC column connection joint with adhesive bonding and self-locking, the typical failure process included at least two load fluctuations with multiple peaks. Moreover, the presence of adhesive bonding substantially improved the slip stiffness of the connection joint specimen relative to specimens with only self-locking. Additionally, the taper angle of the square tube influenced slip stiffness; however, the influence of the taper angle decreased with increasing contact area. Finally, regardless of the surrounding type and taper angle, the first peak load increased with the larger contact area, and the type of steel bearing surrounding the RC column had an obvious influence on slip stiffness. Furthermore, a finite element model was proposed to simulate the working performance of the proposed connection joint based on experimental data. The simulation showed that joint failure occurred mainly owing to the buckling of the vertical stiffeners and the outward deformation or tearing of the square rings, and the tilting of the joint due to local falling off of the structural adhesive must be prevented.