Pseudo-static Experimental Study Of H-shaped Beams To Cold-formed Square Steel Tube Columns Connections With Different Outer Diaphragm

Nowadays, with the rapid development of economy, more and more energy beingconsumed, development of green steel is able to build resource-saving society andenvironment-friendly society. In recent years, more and more steel residential buildingsis being building, and the complex and large-span steel space structures buildings arebecoming increasingly popular with the isotropic of the square steel tube columnreflecting nicely.In the environment of society needs, a new connection of the outer diaphragmconnections between cold-formed square steel tube columns and steel beams ispresented. Its column using cold-formed square steel tube column and the beam-columnconnections using traditional flange plate type and beam flange welded with cove (outerdiaphragm) to strengthen the beam flange of the connection. The purpose of the outerdiaphragm is to protect beams connecting welds and force plastic hinge to move to thenormal segment beam flanges.In this paper, by the way of experimental study and FEM analysis, the changes ofthe failure mechanism, node capacity, deformation capacity, energy dissipation capacity,stiffness degradation and stress changes is systematically studied, to provide referencefor design and engineering applications and lay the theoretical foundation for futureresearch of the outer diaphragm connections between cold-formed square steel tubecolumns and steel beams. The main objectives of the research are as follows:(1) Through pseudo-static experimental study, describing the experimentalphenomena and plastic hinge formation process of the four new outer diaphragmreinforced connections with a reduced scale ratio of1/2and drawing the curves of theshear–displacement of column end, the moment-rotation (M-θ), the skeleton curveand the stiffness degradation and also combining with the strain changes of the outerdiaphragm, the beam flange and the panel of the connections to comparative analyzedthe seismic performance comprehensively of the connections. The experimental resultsshow that the plastic hinges formed at the beam flanges nearby the connections, andthere are no obvious deformation of the column, panel and outer diaphragm. The arc-type outer diaphragm reinforced type connection’s force transferred smoothly.Therefore, the arc-type outer diaphragm reinforced type connection should bepreferentially adopted in engineering.(2) By FEM software ABAQUS, four new outer diaphragm reinforced connectionsare numerical simulated. The FEM results and the experimental results of the failuremodes, carrying capacity changes, stress transfer and equivalent viscous damping factorEtc. by the way of comparative law. Results showed that there was consistencycompletely among the FEM results and the experimental results.(3) On this basis, by the way of changing axial compression ratio of the arc-typeouter diaphragm reinforced type connection, additional analysis was done. Resultsshowed that the failure modes of connections were changed. With axial compressionratio increases, the failure modes of connections were the beam hinge failuremechanism, the panel failure mechanism and the column hinge failure mechanism. Thecolumn flange stress increases with axial compression ratio increases, and the P-△effects on the connections increase with the column loading point displacement increase.So, in engineering applications, axial compression ratio should be strictly controlled.