Finite Element Analysis On Shear Capacity Of Concrete-filled Rectangular Steel Tube Connection With Through Diaphragm

Concrete filled steel tube structure has the advantages of high bearing capacity, high stiffness and excellent seismic performances, quick construction. Besides with the above advantages, the concrete-filled rectangular steel tube structure with through diaphragm also has the advantages of convenient weld processing,delight, avoiding convex corner and space saving. Based on part of the existing test data, this paper studied the shear performance of concrete-filled rectangular steel tube connection with through diaphragm through analysis and finite element numerical simulation. In this paper, the main work is as follows:(1) The part of the existing theoretical model and design formula proposed by domestic and foreign standards or researchers were organized,the advantages and limitations of each calculation method were analyzed.The accuracy and applicability were studied through the analysis and comparison of partial test;(2) The finite element model of through diaphragm connection was established using ANSYS. The validation showed the finite element model could accurately simulation the response of through diaphragm connection under low cyclic loading, so it could replace part of experiment to study the mechanical behavior of through diaphragm connection.(3) Based on the finite element model of through diaphragm connection established in the third chapter, the force transfer mechanism and the effect of the components geometry size in panel zone and the slab effect on the connection shear capacity were studied. Result showed that under shear failure mode the shear capacity is mainly provided by the web of the steel tube and core concrete, the contribution of the steel tube flange and diaphragm is to transfer the load from the beam, and the core concretedevelops diagonal strut mechanism to resist shear. The thickness of diaphragm and steel tube in panel zone have great influence on the shear capacity, while the influence of steel beam flange thickness and width is relatively small. The concrete slab can improve the shear capacity and has effect on the failure mode of connection; larger axial load ratio can significantly reduce the shear bearing capacity and ductility of through-diaphragm connection, while the axial load ratio less than 0.4 can enlarge the shear bearing capacity and the axial load ratio less than 0.35 can improve the ductility of connection. Therefore it is suggested to limit the axial load ratio at values less than 0.4 and its influence should be considered in the analysis and design of through-diaphragm connections. Hereby, the suggestion about considering the influence of axial compression ratio was proposed for the formula 2-1, and confirmed by the experiment data, its calculation values would be more close to the test value.(4) The optimized design of through diaphragm connection structure details was completed using the numerical analysis of finite element. The result suggest that the structure details of extending diaphragm with chamfer could be used to design the connection, the air holes on the diaphragm should be set up along the orthogonal spindle; “tcx=14.2mm,td=9.5mm,bbf=138.8mm” could be taken as reference to design the connection specimen by changing the material thickness and geometry dimension of component in the panel zone.This paper based on the project of National Natural Science Foundation“Seismic performance of the panel zone of diaphragm-through connection on concrete-filled rectangular steel tubular column”(51268054). The project aims to study the seismic performance of the panel zone of diaphragm-through connection on concrete-filled rectangular steel tubularcolumn through the low cyclic loading experiment and research on calculation methods of shear capacity of connection panel zone. The content of this paper belongs to early stage of the project, mainly to provide a reference for the connection experiment scheme design.