Analysis On Shear Performance Of Frame Joints With Concrete-Filled Square Steel Tube Column And Unequal Depth Steel Beam

Due to the constraints of the building space and the requirements of the use of function,conventional concrete-filled steel tubular column joints cannot meet the specific needs well,the form of abnormal joints with concrete-filled steel tubular column and unequal depth steel beam can play an important role.At present,many scholars have extensively studied the conventional joints of concrete-filled steel tubular column,but there are few studies on the frame joints with concrete-filled steel tubular column and unequal depth steel beam,especially the failure mechanism analysis involving such abnormal joints.In this paper,based on the existing tests,by means of finite element simulation and theoretical analysis,the shear mechanical properties of the frame joints with concrete-filled steel tubular column and unequal depth steel beam are studied,and reasonable suggestions for joints design are put forward.The main research works are as follows:1.The finite element model of the frame joints with concrete-filled square steel tubular column and unequal depth steel beam was established.The finite element software ABAQUS 6.14 was used to numerically simulate the seismic performance of the joints under low cyclic horizontal load.By comparing the simulated hysteresis curves,skeleton curves and stress clouds,it was found that the simulated calculation results matched well with the experimental test results,and its failure mode was basically the same as the experimental description,which verified the reliability of the finite element model.Based on the test and finite element simulation,the force transferring mechanism and failure mechanism of joints were deeply analyzed,and the influence laws of four key parameters on the seismic performance of the joints were studied,including the height ratio of the left and right beam,the axial compression ratio,the yield strength of the steel tube and the strength of the core concrete,which provided an important basis for subsequent theoretical analysis.2.The formula for calculating the shear bearing capacity of joints with concrete-filled square steel tubular column and unequal depth steel beam was derived.On the basis of experimental research,combined with finite element analysis,it is found that the typical failure mode of panel zone is shear diagonal compression damage in the top core region,and then the theoretical model of shear resistance in the panel zone of joints with concrete-filled square steel tubular column and unequal depth steel beam is established.A method for calculating the shear capacity of the joint core area is put forward,which is composed of the steel tube web,the main compression strut and the confined compression strut in the concrete core.Compared the difference between the calculated values of shear bearing capacity established based on different shear models,the test values and finite element simulation values,which verified the correctness of the force transferring mechanism and bearing capacity calculation formula.3.The design and construction suggestions of the joints with concrete-filled square steel tubular column and unequal depth steel beam were put forward.Based on the experimental phenomena and finite element analysis results,and referring to the relevant research and the design requirements of the current codes and regulations for conventional joints,the design of abnormal joints with unequal beam depth on both sides is improved,and the reasonable seismic design and construction measures are proposed,so as to provide reference basis for practical application in subsequent projects.