Experimental study on hysteretic behavior of L-shaped SRC column-concrete beam joints

To study the hysteretic behavior of L-shaped steel reinforced concrete (SRC) column-concrete beam joints, four planar joint specimens and seven 3D joint specimens were tested under the quasi-static state, and the varying parameters included steel form for cross section of column, axial compression ratio, horizontal loading angle and participation of floor slab. The failure mode, hysteresis curve, bearing capacity, stiffness degradation, energy dissipation capacity, displacement ductility and storey drift angle were compared and analyzed for those specimens. The test results show that for planar joints, the main failure mode is the shear failure, while for 3D joints, their failures are attributed to the plastic hinge appeared in the beam end. For RC 3D joints with floor slab participated, the main failure modes shall be the flexural failure of floor slab and the plastic hinge appeared at the bottom of beam. The hysteresis curves of specimens with solid-web steel shall be more plump than those of specimens with hollow-web steel. The bearing capacity of planar joints is larger than that of 3D joints, but their energy dissipation capacity, displacement ductility and collapse resistance shall be inferior to those of 3D joints. The existence of floor slab shall be beneficial to the enhancement of bearing capacity and the stability of stiffness for the joints. A large axial compression ratio can increase the bearing capacity and the initial stiffness of specimens. The storey deformation capacity of L-shaped column frame joints is larger than the storey drift angle limit specified by code. By introducing the loading angle, the calculation model of shear capacity is proposed for L-shaped SRC column-beam 3D joints, and the model can reflect the forcing mechanism of shear failure in the core of joint.