Study Of Interface Nonlinear Effects On The Overall Mechanical Properties Of Steel-Concrete Composite Beams

Steel-concrete composite beam is a new type of structure which is developed on the basis of concrete and steel structure. It combines the steel girder and concrete wings together into a whole by using shear connector or opening steel boards. Composite beams give full play to their respective advantages of the two materials, forming the structure with big stiffness, ductility and high load bearing capacity. Composite beams have been made more widely used in the field of building and bridge structure. The biggest difference between composite beam and ordinary beam is the presence of shear connectors, which will cause relative slip between two materials at the interface under loading. It will have a great influence on the mechanical properties of composite structures. In the study of existing interface behavior, for the force behavior of shear connectors and load-slip consider nonlinear relationship also were not very deep. Additionally, nonlinear behavior of theoretical analysis and calculation of the interfacial slip are also not perfectly considered yet. Therefore to carry out the study of nonlinear behavior of the interface and its effect on the overall mechanical behavior of the beam is necessary. The main contents are as follows:Based on the National Natural Science Foundation of Youth "nonlinear analysis on the steel-concrete composited beams coupled with creep", push-out teset of steel-concrete composite structure has been carried out to get load-slip relationship of shear connectors. And through summary to the related literatures, some load-slip curves for different types of shear connectors were selected and characteristics of nonlinear load-slip relationships for different types of shear connectors were analyzed.Secondly, the thesis reviews the basic theory of the composite beams’interface behavior and mechanical behavior. Additionally, the thesis classifies the calculated deformation of ultimate bearing capacity and modification of composite beams including consideration of each slip and not consider the case when the slip. In addition, the thesis analysis the interfacial working mechanism of composite beams and two shear connectors’mechanical properties and load-slip relationship.Thirdly, the thesis uses ANSYS which is a finite element analysis software to model steel-concrete composite beams and analysis the nonlinear constitutive relation of each unit with selecting reasonable simulation methods of the interface and unit connection. On the basis of these, it will establish a more accurately finite element model of the interface behavior.Finally, through analyzing difference of various shear keys’constitutive relation, the thesis will get the characteristics of the shear-slip relationship, including elastic stage, plastic stage and decline stage. Then it will include the shear-slip relationship of different shear keys into the finite element model, and it will analyze the calculation results of the composite beams including the ultimate bearing capacity, deflection, slippage and strain distribution. In final, the thesis will discuss the different constitutive relation of the shear key how to influence the mechanical properties of the composite beams.