Analysis Of Steel-concrete Composite Beams With Interface Slip By Finite Element Method

Although steel-concrete composite beams (hereinafter referred to as composite beams) possesses many advantages, such as high strength, high stiffness and good ductility, interface slip exists always in composite beams, which will reduce composite effect and stiffness of composite beams and increase deflection. In this way, it is imperative to investigate interface slip and its effect on the behavior of composite beams is necessary. If interface slip and deflection are to be calculated, closed solutions can be only obtained for simple cases, such as for simply supported beams with simple load cases. For continuous beam it's difficult to obtain closed solution. Moreover the closed solutions are often too long and too complicate for application. With finite element method it is efficient to calculate interface slip and deflection and there is no restriction of loads and supports. The key step for finite element method is establishing element stiffness matrix, which is derived in this paper by using three methods, which are the total potential energy, the principle of virtual work and the direct stiffness method. In addition the interface slip and deflection of a simple supported composite beam is calculated by using own finite element program and the results are compared with those of the closed solutions. It shows a good agreement and the difference of both results is small and within1%. Thus the element stiffness matrix derived in the paper is correct and can be used in finite element program for solving a large number of practical engineering problems.In this paper, using own finite element program to calculate and analyze the interface slip of composite beams under various loads which decreases with increasing shear connector stiffness. And analyzed according to the form of the distribution of the cross-section shear force to arrange the shear connector can effectively reduce the interface slip. In addition, the distribution of the interface slip of cantilever is different from simply supported beam; and then analyzes the effect of interfacial slip on interface shear flow, steel beam axial force, deflection and the redistribution of internal forces. The distribution of interface shear force is more close to the ordinary beam with decreasing interface slip. In simply supported case, the maximum point of axial force of steel beam of composite beams will be more near to the loading point with the decrease of interface slip. The deflection also decreases with the decrease of interface slip, and the influence of interface slip for the redistribution of internal force will be smaller with decreasing interface slip.