Research On Bearing Capacity Of Fabricated Square Steel Tubular Column-Truss Beam-Inclmed Support Joints

The prefabricated building steel structure has the advantages of good seismic performance,easy installation after disassembly,high construction efficiency,etc.It is one of the green structural systems that best meet the requirements of sustainable development and comprehensive benefits.The square steel tube column-truss beam frame structure with braces is a new type of layer-assembled steel structure,where the column is a square steel tube column with flange plates and diagonal braces,and the beam is an open-web truss beam,which uses high strength Bolt for connection.Oblique braces are provided at the upper and lower 1/3 of the square steel tube column to strengthen the connection of the connections and resist the horizontal and vertical loads together with the frame.The processing and installation process of the connection is simple and easy to implement,which means it can be quickly assembled and has broad development prospects.Therefore,in this paper,the square steel tube column-truss beam connections with and without braces are taken as the research objects,and their bearing capacity,stiffness,ductility,energy dissipation capacity,and failure mechanism are studied.First,monotonic loading and cyclic loading tests on two full-scale specimens,which are square steel pipe columns and truss beam joints with braces,were carried out.By observing the whole loading process,the failure mode and force transmission mechanism of the specimen are analyzed.By whether the connections with or without braces,as well as their loading method,the failure modes of the connections,the force transmission path,the F-Δ curve,the difference between the east and west sides,the ductility performance,the consumption,and other anti-seismic performance indicators,are compared between the specimens.It can evaluate the connections and provide a valid basis for the later establishment of the finite element model.Then based on ABAQUS software,considering the nonlinearity of material and geometry,the finite element model of the square steel tube column-truss beam connections with and without braces under monotonic load is established.The basic parameters of the model and the simplified processing of special positions are introduced respectively.By comparing the results of finite element analysis and specimens J2-4-m and J2b-4-m,the effectiveness of the model is verified.Based on the verified finite element model,parameter analysis was carried out.The influence of the axial compression ratio and column thickness on the failure mode of the square steel tube column-truss beam connections without braces is proposed,and the limit values of the axial compression ratio of column failure and beam failure are proposed;The connections without bracing were optimized by a reasonable combination of square steel tubular columns and truss beam sections;the influence mechanism of the thickness of braces plate and the cross-section of braces on the connections of braced square steel tube-truss beam connections were analyzed,and an optimization scheme for braces was given.Finally,the research in this paper was summarized and further study directions were pointed out.