Theoretical Analysis On Mechanical Performance Of Joint Between Concrete-filled Square Steel Tubular Column And Composite Beam With U Shape Steel Plate Encased Concrete

Composite beam with U shape steel plate encased concrete is a new type of composite beam with effective combination of steel and concrete material. This new type of composite beam with U shape steel plate encased concrete consists of three aspects, U shaped-steel is cold bended by thin steel plate, or welded by cold-formed steel,U shaped-steel is filled with concrete to form the rib of T shape beam, and the flange of T shape beam is cast-in-situ concrete plates. Concrete and U shaped-steel work together by applying adequate shear connectors. The composite beam has such adventages that it is a reasonable structure,has a good fire resistance performance, and has a high bearing capacity and large stiffness. So far joints composed of this composite beam and Concrete-filled square steel tube are not widely resaearched, which confined its'spread and application.According to the characteristic of composite beam structure, this paper propose a new kind of joint composed of this composite beam and Concrete-filled square steel tube. by using finite element analysis, failure mechanism and earthquake resistant behaviour is discussed.This paper mainly researchs failure mechanism and mechanical characteristic of the composite structure joint. Flexural capacity formula is rasied under negative bending moment, together with flexural capacity formula under positive bending moment. The area of negitive bending rebar is calculated. According to the calculation stipulation from Code for design of steel structures, shear capacity calculation formulas of composite beam are raised. By contrasting shear capacity and bending capcaity of the composite beam,results indicates that bending capcaity is the major factor that determine the capcaity load of composite beam.By utilizing finite element analysis software ANSYS, analysis of two joint in ultimate loads is made, meanwhile, bond-slip between U shaped-steel and concrete is considered, and resonable constitutive relation and failure criterion are choosen. By contrasting the yield load and displacement of two joints in monotonic loading, the results show that the yield load and yield displacement of two joints differs little.Nonlinear finite element analyses of joint of the composite structure are conducted under low-reversed cyclic loading. Stress distribution in the joint panel zone and the failure mechanism is accurately simulated. The results such as the stress distribution and ultimate bearing capacity of the structure are obtained. Finally, the entire force-displacement curves are obtained by the whole nonlinear analysis of composite frames subjected to cyclically loads. Feasibility of this new joint is verified by contrast bearing capcaity,ductility and Dissipation characteristics. By establishing different models,the impact on Hysteretic performance of axial-load ratio and concrete compression strength is analysed.