Experimental Study On Seismic Behavior Of3D Steel-hoop RC Beam-column Joints

In ordinary RC beam-column joint, the longitudinal beam bars from two diffidentdirections crisscross with high-density, the same as the longitudinal column bars andstirrups, the overcrowded situation in joint brings difficulties on concrete placement andbad effect on the quality of concrete. Considering the above situations, a new joint modewas put forward by our team, which is based on the tradition RC beam-column joint,named “Hoop-steel Joint”. Subsequently, several experiments about this new joint onseismic behaviors were carried out and conclusions were made.In fact, the beam-column joint is in the form of3D, which undertakes the bendingmoment, shear force, axial force and torque moment from beam, column and slab underthe multidirectional earthquakes. The result on seismic behavior and failure patterns ofjoints in3D are different from those of joints in2D, so the seismic performance ofjoints in3D under bi-directional loading is necessarily to be studied.In this dissertation, a hoop-steel joint in3D with floor slab named SGJ-1under lowreversed45-degree cyclic bi-directional loading were completed; the seismic behaviorand failure patterns were analyzed in detail. Models were established in finite elementprogram ABAQUS to make comparison with SGJ-1.Main conclusions are as follows:①Comparison with ordinary RC beam-column joint, the overcrowded situationof joint is ameliorated in hoop-steel joint, which brings convenience for concreteplacement and guarantee of quality.②SGJ-1failed because of the joint shear failure after the beam bars yielded,butit still showed certain bearing capacity, displacement ductility.③The Hoop-steel joint in3D owns better shear capacity than the same joint in2Dbecause of the assistance of slab and transverse beams.④The loading method makes great effect on the seismic behavior of joints in3D.The displacement ductility and energy dissipation capacity are worse when specimensin3D are under the45-degree cyclic bi-directional loading.⑤The slab stays in complicated mechanical state when specimens are under themultidirectional earthquakes. It is not fit to define specific area on each side of the beamwhere the reinforcement participates in the resistance of the beam against negative flexure when the seismic behavior is been analyzing. Further studies on the mechanicalproperties of slab need to be taken.