Research On Seismic Performance Of Three Dimensional Steel Frame Structure With Cast Steel Joints

For steel frame structure,beam column joints play the key role as component force transmission center of beam and column and also provide relatively constraint conditions for beam and column,which play a crucial role in the seismic performance of frame structure.Suitable beam-column joints will reduce the seismic response and improve the seismic performance of frame structures.Cast steel beam-column joints for rectangular tube steel column-H shaped steel beam is a novle steel frame beamcolumn joints using precast cast steel connector as strengthening member.It has many advantages such as clearly transmission force,simple structure and convenient construction.The study on influence of the new joints on the seismic performance of steel frame structures is still lacking.In addition,the seismic performance study of steel frames is mostly conducted on plane frame model at present,and the performance of three dimensional steel frames is less considered.But the actual frame structure form is usually three dimensional,and have difference seismic performance with plane frame.Therefore,it is necessary to study the seismic performance of three dimensional steel frame structures with cast steel joints.This study take three dimensional steel frame structures with cast steel joints as the research object,adopts spring element to simulate the mechanical properties of the actual beam-column joints,the frame structure under low cycle reciprocating was studied and deformation capacity,energy dissipation capacity,strength characteristics and stiffness characteristics are revealed.The influence on frame structure seismic performance of all welded beam-column joints and cast steel joints are compared.The main research contents and results are as follows:(1)The model of steel frame beam-column joint was established by finite element software,and the moment-angle curve of cast steel beam-column joint and all-welded beam-column joint were solved,and the initial rotational stiffness and other mechanical properties of the joints were analyzed.A spring-bar model of three dimensional steel frame was established by adopting rotation spring element to simulate the mechanical properties of beam-column joints.Compared with the experimental results of the existing three dimensional steel frame structure,it is found that the difference between the simulation results of the spring-bar model and the experimental results of frame with the all-welded beam-column joints is 10%～13%,and that of the frame with the cast steel beam-column joints is 0.1%～11%.It is proved that the spring bar model of three dimensional steel frame is feasible to analyze the performance of frame structure.(2)Parametric finite element analysis of seismic performance of three dimensional steel frame structures was carried out.With different outer diameters and wall thickness of square steel tubes,the initial rotational stiffness and other mechanical properties of different joints were simulated by rotation spring element,and the parametric seismic performance of steel frames with cast steel beam-column joints and welded joints under low cycle reciprocating loading was analyzed.The hysteresis curve and skeleton curve of two kinds of steel frames with cast steel beam-column joints and all welded joints were compared,and the ductility,energy dissipation capacity and stiffness degradation characteristics were analyzed.The results show that as the outer diameter of square steel tube column increases from 150 mm to 300 mm,and the wall thickness increases from4 mm to 16 mm,the hysteresis curve of steel frame with cast steel beam-column joints is fuller,and the ductility coefficient and energy dissipation coefficient of steel frame with cast steel beam-column joints increase by up to 15% and 26% respectively,compared with the steel frame with all welded beam-column joints.It shows that the mechanical properties of the joints have a great influence on the seismic performance of the space steel frame,and the cast-steel joints can significantly improve the seismic performance and energy dissipation capacity of the space steel frame.