Study On Mechanical Performance And Application Of Outer-shell Connections For CFST And Steel Beam

With the higher design and the better seismic performance of buildings, concrete-filled steel tube structures are being increasingly used in structural engineering. Joints are the crucial part of building structure, they’re rather important for the study of concrete filled steel tubular column and the connections for steel beam. The subject of this essay is focused on the new type outer-shell end-plate connections for concrete filled steel tubular column and steel beam,and came to the following achievements by the stress analysis of joints and plane frames.Firstly, after studying the benefits and disadvantages of different joints, research of concrete filled steel tubular column and steel beam domestic and abroad, concluded a outer-shell connections for concrete filled steel tubular column and steel beam, gave the design method.Finite element modeling method was made to guarantee the credibility of the research, and use this method to compare with existing trial.Secondly, through the establishment of outer-shell and without outer shell concrete filled steel tubular columns and steel beam connections and analyze the bearing performance of new type joints under monotonic effect, concluded that how the outer shell concrete filled steel tubular columns and steel beam connections work in the process. Then analyze the plots changes of joint M-θr with different parameters, use the analysis results to establish a M-θr finite element model that fits outer-shell connections for concrete filled steel tubular column. And the results show that due to the restriction effect of outer-shell to the joints, the joints with outer-shell have greater initial stiffness and bearing capacity and better seismic performance. The main factors that affect initial stiffness and bearing capacity of joints are steel yield strength,end-plate thickness,steel ratio,linear stiffness ratio of beam to column and outer-shell thickness. The established M-θr finite element model fits the finite element calculation,provide theoretical basis for the design and engineering practice of outer-shell end-plate connections for concrete filled steel tubular column and steel beam.Thirdly, selecting specimen joints by end-plate thickness, steel ratio and axial compression ratio, and test them under cyclic loading. Analyze the damage characteristic, M-θr hysteretic curve and energy dissipation capacity under cyclic loading. Then study he tectonic reworking of joints and its effect. The results show that with the energy dissipation of end-plate thickness,steel ratio and joints, there has been an increase of equivalent viscous damping coefficients and accumulated hysteresis dissipated energy. The hysteretic curve of moment and rotation relationship is rather plum, it shows the promising seismic performance of end-plate connections for concrete filled steel tubular columns and steel beam with outer-shell. By weakening steel beam flange, flange level haunched, and increased end-plate stiffener as different structural measures for the study of the variable joints performance, found that increased end- plate stiffener would most enhance the ultimate flexural resistance and seismic performance of the joint.Fourthly, establish a concrete filled steel tubular frame of outer-shell connections for concrete filled steel tubular column, study its working mechanism and seismic performance.Systematically analyze the effect of different parameters to concrete filled steel tubular frame,and to its hysteretic behavior. The study shows that Frame specimen load- displacement hysteresis curve form similar, are relatively full, no pinch shrinkage phenomenon happens,indicates that outer-shell connections for concrete filled steel tubular column has relatively good energy dissipation capacity to concrete filled steel tubular frame. With the increase of axial compression ratio, steel ratio,linear stiffness ratio of beam to column and outer-shell thickness, the equivalent viscous damping coefficients and accumulated hysteresis dissipated energy of frame also increased. Respectively study the main parameters that effect outer-shell connections for concrete filled steel tubular column and concrete filled steel tubular frame loading-displacement relationship, obtained the law of how different parameters effect frame loading- displacement hysteresis curve.