Research On Seismic Behavior Of Welded Joints Of Strengthened By Outer Arc Plat Of Concrete-filled Circular Steel Tube Columns And Steel Beams

In recent years,CFST-beam joints have been widely used in prefabricated buildings and long-span buildings.Based on the advantages of the joint,such as good ductility,High bearing capacity,etc.,the derived arc end plate single side bolt joint has become one of the important topics of domestic and foreign researchers.However,under the repeated earthquake load,the type of joint is prone to bolt relaxation deformation,brittle fracture,and structural instability failure.How to design new joints with good seismic performance and study their mechanical properties are of great significance.In view of this problem,this paper puts forward a new type of welded joints of strengthened by outer arc plat of concrete-filled circular steel tube columns and steel beams.The seismic performance of the joint specimen is discussed by the method of test and simulation.This study increases the richness of this kind of joint,and provides more possibilities for engineers to choose the joint.The main content and research result of this paper:1.This paper presents a new type of welded joints of strengthened by outer arc plat of concrete-filled circular steel tube columns and steel beams.According to the scale of 1:2,two new joint specimens and one arc end plate single side bolt joint specimens are designed.Except for the different stiffness of steel beam,the other parameters of the two new joint specimens are the same.The energy consumption and ductility of three joints are studied by the reciprocating load test.The results show that the new joint has good energy consumption and ductility and is superior to the curved end plate-single-sided bolt joint;the ultimate bearing capacity and initial stiffness of the new joint are higher than that of the arc end plate single side bolt joint;the increase of the steel beam stiffness has a significant effect on the improvement of the ultimate bearing capacity of the new joint;the strength degradation and stiffness degradation of the three joint specimens are not obvious;The effect of weld defects on joint ductility is significant.2.On the basis of the experiment,the three-dimensional model of the new joint is established,and the hysteretic and skeleton curves of the joint are obtained through the finite element method.At the same time,the parameters affecting the seismic resistance of the joint are analyzed.The research shows that the new node hysteresis curve calculated by the finite element method is fuller than the test curve,but the two agree well with each other.At the same time,the final failure form of the model is the failure of the plastic hinge at the end of the beam,which is consistent with the failure mode of the test;With the increase of axial compression ratio,the ultimate load and the initial stiffness of the new type of arc plate reinforced circular concrete filled steel tubular column steel beam welded joint are significantly reduced.The change of axial compression ratio will affect the failure mode of the new type of arc plate reinforced circular concrete filled steel tubular column steel beam welded joint;the change in the strength of the concrete in the steel tube will have no significant effect on the ultimate bearing capacity of the joint.The influence of beam-column stiffness ratio and steel yield strength on the ultimate bearing capacity of new joints are significant.3.On the premise that the model is reliable,according to the results of finite element analysis,the formulas for calculating the horizontal ultimate bearing capacity of the column top and the ultimate bending bearing capacity of the joint of circular concrete-filled steel tubular column and steel beam welded joint with multiple parameters are fitted.The formula takes into account some important and commonly used parameters,and the formula is simple,which can provide quick help for estimating the bearing capacity of such joints.