Research On Seismic Performance Of Internal Partition Plate Joints In Flat Steel Tube Concrete Columns And H-shaped Steel Beams

Flat steel tube concrete columns refer to rectangular steel tube concrete columns with a crosssectional aspect ratio between 2-4.They have excellent seismic performance,are easy to standardize and scale production,and are an important structural form of prefabricated steel structure buildings.Compared to traditional steel tube concrete columns,flat steel tube concrete column structures can solve the problem of column edges protruding indoors.However,the existing connections between flat steel tube concrete columns and steel beams have problems such as occupying the outer space of the column,affecting the indoor appearance,complex force transmission paths,and being prone to column end failure.In response to the above issues,this article proposes a flat steel tube concrete column H-shaped steel beam internal partition connection node with reinforced short beams that is easy to quickly assemble.The seismic performance of this new type of beam column node was studied through a combination of theoretical analysis,experimental research,and finite element numerical simulation.The main contents include:(1)9 seismic performance tests were conducted on the interior partition joints of flat steel tube concrete columns and H-shaped steel beams.A reciprocating cyclic loading test was conducted on three types of node specimens of steel beams with strong axis centered,weak axis centered,and weak axis eccentric using beam end loading.The hysteresis curve,skeleton curve,stiffness,ductility,energy dissipation capacity,failure process and mode,as well as the strain distribution of each component in the core were analyzed,and the influence of different connection positions of steel beams on the seismic performance of nodes in flat steel pipe columns was studied.The results show that all three types of nodes have high bearing capacity and good ductility,and the hysteresis curves are all in a full shuttle shape,with good energy dissipation capacity.The main failure modes of nodes are steel beam base material tearing failure and beam end plastic hinge failure,achieving the goal of beam end plastic hinge displacement.(2)A refined finite element model was established for the internal partition plate joint of flat steel tube concrete columns and H-shaped steel beams,considering both material and geometric nonlinearity.The stress development process and reasons for stress concentration of each component of the joint during loading and unloading were analyzed.The geometric parameters(beam flange thickness,internal partition plate thickness,and steel tube column wall thickness),physical parameters(steel strength,concrete strength),and The influence of load parameters(axial compression ratio)and different node forms on the bending bearing capacity and initial stiffness of nodes.The results show that the hysteresis curve,skeleton curve,load-bearing capacity,and failure mode of the specimen calculated by the finite element software are basically consistent with the experimental results,verifying the authenticity and reliability of the model.There is a phenomenon of stress concentration at the connection between the steel beam and the reinforced short beam flange.The thickness of the reinforced short beam flange and the yield strength of the steel have a significant impact on the bearing capacity of the node.The thickness of the inner partition,the thickness of the steel pipe column wall,the axial compression ratio,and the concrete strength have almost no effect on the bearing capacity and stiffness of the node.The stiffness of the outer ring plate,through partition,and inner partition are basically the same,However,the ultimate bearing capacity of the outer ring plate joint has increased by about 10% compared to the other two types of joints.(3)A study was conducted on the mechanical mechanism of the internal partition joints of flat steel tube concrete columns and H-shaped steel beams,clarifying the force transmission path and bearing mechanism of the specimen nodes and core areas.Based on the yield line theory,a formula for calculating the bending bearing capacity of this type of joint was proposed.And the theoretical value calculated by the formula was compared and verified with the actual value of the experiment.The error between the theoretical value of the proposed node bearing capacity calculation formula and the experimental and numerical simulation results is within 10%,which is in good agreement.