Shear Behavior Of External-diaphragm Connection Between Rectangular Tubular Column And H-shaped Steel Beam

Rectangular concrete-filled steel tube frame structure has been widely used in high-rise buildings at home and abroad due to excellent mechanical properties and geometric advantages.As one of the three connection modes of square steel tube column and steel beam recommended in the Technical Specification for Structures with Concrete-filled Rectangular Steel Tube Members(CECS159:2004)in China,the external-diaphragm connection has its unique advantages.At present,at home and abroad,the research on the shear performance of external diaphragm connection under the shear failure mode in panel zone is insufficient.In this paper,the combination of experimental,finite element simulation and theoretical analysis is used to study the shear capacity of the panel zone of the external-diaphragm connection.On the basis of consulting a large number of relevant literatures at home and abroad,this paper summarizes the current research status of the external diaphragm connection,and clarifies the problems existing in the existing research,and determines the research direction of this paper.In order to study the shear capacity in panel zone of external diaphragm connection,four rectangular steel tube columns and H-shaped steel beam external diaphragm crossshaped joint specimens were designed and the low-cycle repeated load tests were carried out.The failure characteristics of specimens and the shear deformation curve of the panel zone are obtained.According to the experimental phenomenon,the influence of the thickness of steel tube,the width and thickness of external diaphragm on the shear bearing capacity in the panel zone of the joint is analyzed.The ANSYS software was used to simulate the low-cycle repeated tests of rectangular steel tube columns and H-shaped steel beam external diaphragm connection,and a full-scale three-dimensional finite element solid model considering material nonlinearity and geometric nonlinearity is established.The failure modes,deformation characteristics and shear-shear deformation curves of the panel zone of the joints are compared.Based on the proved finite element model,the influence of different parameters on the shear capacity of the panel zone of the external diaphragm is analyzed.The calculation method of the shear capacity of the core area of the existing external diaphragm connection is summarized,and its advantages,disadvantages and applicability are expounded.Based on the experimental results and finite element simulation,the force transfer mechanism is clarified,the force mechanism of the panel zone of the external diaphragm is analyzed.The calculation model of the shear resistance of the panel zone is established.Based on the superposition theory,the calculation formula of the shear capacity of the panel zone is derived.The experimental result is used to verify the theoretical results,which proves the accuracy of the theoretical calculation results.