Failure Mechanism And Seismic Performance Of The Endplate Joints For Concrete Filled Thin-walled Steel Tubular Frames

Thin-walled concrete filled steel tube is mainly used in low-rise buildings because ofthe good performance of high capacity, good ductility and toughness, fabrication andconstruction, fire resistance, and economic characteristics. Intensive research has been doneabout thin-walled steel tube concrete column, but there is less previous work for thethin-walled concrete filled steel tubular column connections. It has been confirmed that theribbed thin-walled concrete filled steel tubular column connections static has a goodmechanical performance, so the research of failure mechanism and seismic performance ofthe endplate joints has great theoretical and practical value.The research of the seismic performance of framework of thin-walled concrete filled steeltubular beam-column end plate connection node has been done in this research, and themain word has been done as follow:1) The cyclic loading test has been done to four thin-walled concrete filled steel tubularframe beam end plate connections to research the type of end plate and steel pipe thicknessnode failure modes, the hysteresis curve, strength, stiffness, ductility and energy dissipationcapacity impact. The results have shown that the extended end plate connections belong tothe semi-rigid and part-strength node; pouring concrete in the pipe and selecting reasonableconnection measure could make thin-walled concrete filled steel tubular frame beam endplate connection node of good strength stiffness ductility and seismic performance, whichcan be safely and reliably used in multi-story composite frame.2) A nonlinear finite element model has been constructed using the finite element softwareABAQUS, and the accuracy of this model has been proved by the experimental results. Thestandard model of the end plate connections and the extended end plate connections hasbeen constructed and the nonlinear full seismic analysis has been done to the mechanism ofstandard model, the node stress distribution and the working mechanism have beenresearched as well.3) the nonlinear finite element model of endplate connected node and extended end-plateconnection has been constructed to research the related parameters which could affect thenode moment-rotation hysteresis curve, such as: axial compression ratio (n), the end platethickness (tep), the thickness of the steel pipe thicker area (tjc), steel pipe thicker areas Height (hjc), bolt diameter (db), the bolt pre-tension (P), bolt anchorage lengthcoefficient (αi), the strength of steel (fy), the concrete strength (fcu), beam and column yieldmoment (km), beams linear stiffness (ki), the slenderness ratio (λ), steel ratio (α) ofthin-walled concrete filled steel tube flush end plate connection node and the extended endplate connection node of the stiffness and moment-rotation relationship.4) Based on the experimental results and theoretical analysis, reasonable constructionmeasures have been proposed in this paper, such as increasing the thickness of steel tube,adopting welded reinforcement in bolt end and so on, which can improve the stiffness andstrength of the node effectively.