Abstract: In order to consider effects of longitudinal slip and vertical uplift of composite beam connection surface, the governing equations of composite beam bending deformation are established with fundamental unknowns of the longitudinal slip and vertical deflections of sub beams under assumption of sub-beams satisfying Euler-Bernoulli bending theory. By using Laplace transform and its inverse Laplace transform, the analytical solutions of deflection, slip displacement, axial force and bending moment of simply-supported composite beam under uniform load are obtained. Assuming that the material and geometric parameters of the two sub-beams are the same, the effects of the loading mode and the longitudinal slip and vertical uplift stiffnesses of the connection surface on the bending deformation and internal forces of the simply supported composite beam are analyzed. The results show that with the increase of interface longitudinal stiffness, the deflection, slip displacement and bending moment of composite beams decrease first and then tend to be constant, while the axial force of composite beams increases first and then remains constant; And when the composite beam is loaded from the top sub-beam, with the increase of the vertical stiffness of the interface, the deflection and bending moment of the upper beam first decrease and then tend to be constant, while the deflection and bending moment of the lower beam first increase and then tend to be constant; When the composite beam is loaded at the bottom sub-beam, it is opposite to that at the top; The deformation and internal force of composite beams have nothing to do with the vertical stiffness when the upper and lower loads are the same.

Key words: composite beams, longitudinal slip, vertical lift, analytical solutions, parametric study, loading mode