Research On Mechanical Behavior Of The Connection With External Stiffening Ring Under The Static Tension Load

Connection with external stiffening ring;Diaphragm-through connection and Inner diaphragm connection between CFST column and steel beam has been recommended in technical specification for structures with concrete-filled rectangular steel tube members(CECS159:2004).At present,domestic and foreign scholars have done a lot of research on the mechanical properties and design methods of the diaphragm-through connection and inner diaphragm connection.The design formulas for the flexural and shear bearing capacity of the diaphragm-through connection and inner diaphragm connection have been given in technical specification for structures with concrete-filled rectangular steel tube members(CECS159:2004).Although some research work has been carried out by domestic and foreign scholars and some achievements have been made,there is no unified and definite calculation model for the calculation of the bending capacity of connection with external stiffening ring,and the error between the existing theoretical results and the experimental results is quite large.The lag of the design method of bearing capacity seriously restricts the application and popularization of the connection with external stiffening ring in practical engineering.On the basis of summing up the research on the connections between CFST column and H-shaped steel beam and combining with domestic and foreign research experience,the existing problems in the study of the connection with external stiffening ring are clarified,and the problems are studied.In order to investigate the bending capacity of the connection with external stiffening ring,the static tensile tests were carried out on 8 connections with external stiffening ring and the failure mode and the load transfer mechanism of the connection are analyzed.The stress transfer mechanism of the core region of the connection with external stiffening ring is analyzed by measuring the strain distribution and variation of the column flange and web as well as the external stiffening ring during loading process.The failure mechanism of concrete in the core area of steel tube is studied by splitting test of the connection with external stiffening ring.The nonlinear finite element analysis of the test connections is carried out by using the finite element software ANSYS,and the feasibility of the finite element simulation of the static tensile test of the connections with external stiffening ring is verified.The influence of the parameters such as the size of external stiffening ring plate and the thickness of steel tube on the mechanical behavior of the connection is studied based on the parametric analysis of connections with external stiffening ring is carried out.On the basis of experimental results,according to the stress distribution nephogram obtained by finite element analysis,the force transfer mechanism and yield mechanism of the connections with external stiffening ring under tension are analyzed.A method for calculating the static tensile capacity of the connections with external stiffening ring of hollow steel tube and the connections with external stiffening ring of the concrete filled steel tube is proposed,and the accuracy and applicability of the method are verified.The results show that the calculated values of the connections with external stiffening ring of hollow steel tube and the connections with external stiffening ring of the concrete filled steel tube are in good agreement with the experimental values and It can meet the requirement of engineering precision,and can provide reference for the design of the connections with external stiffening ring.