Optimization Design And Mechanical Behaviors Of Concrete-filled Flat Tubular Column-steel Beam Joint

Concrete-filled steel tubular structures have been widely used in building construction because of their eccellent mechanical behavior.The length-width ratio of concrete-filled flat tubular columns is between 2~4,and its width is only 200 mm,which is same as the building wall.So it is easy to meet the requirements of the architectural plane as well as the needs of mainstream household.In addition,this kind of column can be hidden by the wall,so it is beautiful and convenient for users.but the biggest drawback are the constraining force of steel tube to concrete is small,and the lateral stiffness of weak-axis column is low.When the steel beam is connected with the long side of column,the steel tube would buckling under the bending moment of the beam.In view of this situation,a new node connection mode is proposed in this paper.The specific contents are as follows:(1)A new way of concrete-filled flat tubular column-steel beam connection is proposed in this paper based on the research.Because the joint is bolted by through high-strength bolts,so it can be installed on site.Then the nonlinear finite element software of ABAQUS is used to optimize the connection mode.The column-end loading method is adopted,and the inner clapboard is not welded inside the column.The stiffness of the short side direction of the column is large enough,and the beam can meet the design requirements when it is just welded on the column.Additionally,the influence of various parameters on the load-displacement curve is analysed,such as axial compression ratio,concrete strength,bolt pretension,coat plate thickness,beam end plate thickness,stiffener thickness and column tube thickness.It is known that the axial compression ratio,beam end plate thickness and stiffener thickness have significant influence.Moreover,The mechanical performance of the joint is related to the location of the beam.For the middle node,the bearing capacity of the node is the highest when the beam deflection is arranged,and it is the worst when the beam is in the middle.(2)Based on the proposed node connection pattern,3 middle joints and 2 edge joints are designed for the experiment.The production process and test program of the specimen are introduced in detail.The seismic performance of 5 specimen in terms of failure mechanism,hysteresis curve,strength,stiffness,ductility,energy dissipation and strain are studied through the pseudo static test.According to the test results,these joints show obvious characteristics of "strong joints and weak components".With the increase of displacement,the flange and web plate of the beam all buckle,and the beam ends form plastic hinge,showing good bearing capacity and ductility.Besides,the different layout modes of beams have great influence on the bearing capacity,ductility and energy dissipation capacity.The bearing capacity and ductility of the joints which the beams are on the side are significantly higher than those which the beams are on the middle,while the latter has better energy dissipation capacity than the former ones.(3)In the end of this paper,based on the experiment and simulation result,further optimization and analysis of the proposed joint form and the corresponding suggestions for the joint construction are presented.