Study On Hysteretic Behavior Of I-section Column RBS Connections Locally Fill Concrete In Nodal Area

There're many disadvantages in conventional reinforced beam-column joints in steel frames,such as excessive welded plates,difficulty in welding,great difference in strength between strong and weak axes,and influence on building aesthetics by changing the height of beam section.Based on the existing research,this paper proposes a local grouting joints in the nodal area,and its numerical simulation is carried out by finite element software.ABAQUS finite element software is used to simulate the test of weakened joints and concrete filled square steel tubular column-steel beam joints.The results of finite element calculation and test are compared and analyzed,which verifies the reliability of finite element software modeling and analysis.In this paper,the local grouting joint,column web reinforced plate joints and traditional steel joint are all subjected to cyclic loads.By comparing and analyzing the results of calculation,it is concluded that the hysteretic performance of grouted joints in nodal area is excellent.I-section column RBS connections locally fill concrete in nodal area is proposed and compared with the non-weakened joint under cyclic loads.The results show that the plastic hinges of the grouted I-shaped column RBS connections appear at the weakened zone which is a certain distance from the end of the beam,which improves the high stress at the weld of beam and effectively avoids brittle failure of the joints.Compared with the non-weakened joint,although the bearing capacity of the joints has decreased,greatly improves the ductility of the joint,and its hysteretic performance is better.By analysising the impact of six parameters which include concrete height h,concrete strength,thickness of stiffeners t_e,distance from the beginning of weaken section to the end of beam a,length of weaken section b and depth of weaken section c on the bearing capacity,ductility,stiffness degradation and energy dissipation capacity of grouted I-shaped column RBS connections under cyclic loading,the reasonable range of parameters is obtained,it is suggested that the filling height of concrete h can be set to 1.2h_b~1.6h_b,where h_bis the height of beam section,the strength of concrete can be set to C30~C40,the thickness of stiffeners t_ecan be set to 6~10mm,the distance between the beginning point of flange weaken section and the end of beam can be set to 0.45b_f~0.75b_f,the length of weaken section can be set to 0.67h_b~0.83h_b,and the depth of weaken section can be set to 0.22b_f~0.27b_f,where b_fis the beam flange width respectively.ABAQUS finite element software is used to build a three-frame two-storey and two-span steel frame with weakened joints.By comparing hysteretic performance indices under cyclic loads with steel frame without weakened joints and traditional steel frame,it shows that the steel frames with weakened joints have excellent ductility and energy dissipation capacity,which indicates that the weakened joints can effectively enhance the overall seismic performance of steel frames.