Analyses On Dynamic And Static Responses Of Two-layer Composite Beams Using Higher Order Beam Theories

Composite beam, as an excellent member type of structure, may make better use of mechanical properties of each component in the composites, and has been extensively utilized in civil engineering and mechanical engineering. Due to the great deal of demands on the composite beams in various engineering practices, it is necessary to develop more reliable and accurate composite beam models, analyzing methods and numerical simulation programs. Therefore, this thesis seeks to develop several higher-order bending models of composite beam for its dynamic and static analysis, and the dynamic/static responses and the stability analysis of the composite beams are conducted with the finite element method.The Reddy composite beam model, which takes into account the condition of shear force continuity in the interface of composite beams, is estabilished, and the analytical solutions for static response of the composite beam are obtained within the linear elastic range of the materials, using a method of Laplace transformation. Considering the nonlinear material properties of the composite beams, the nonlinear finite element equations are formulated and solved by the displacement incremental method to perform the static analyses of the nonlinear composite beam. The shearing effects on the static reponses and stability analyses of composite beams are mainly investigated in the numerical analyses.The finite element equations and corresponding computer simulation programs for the long term behaviour prediction of the steel-concrete composite beams are, respectively, formulated and implemented. In these finite element equations, both the shrinkage and creep characteristics of the concrete have been took into account, and the concrete layer and steel layer of the composite beam are depicted by the Timoshenko and Kant beam kinematics, respectively. The accuracy and superiority of the proposed finite element model are verified through the result comparisons between the present fininte element modle and the 3D thick shell finite element model.Based on the Kant higher order beam theory and the constrained energy principle, the hybrid and displacement-based finite element equations for the static analyses of higher order composite beams are formulated, and then the corresponding finite element programs are implemented. Moreover, both the advantages and disadvantages of the two finite element models are discussed. Using the program developed, the effects steming from the interfacial friction and incompressibility on the mechanical behaviors of the composite are studied.Another dynamic finite element equations for the composites are formulated, in which each layer is depicted by the Kant higher order beam theory, and then the corresponding finite element program is developed, by which the dynamic characteristics and transient responses of the composite beams are studied. The model accuracy of the Kant composite beam is demonstrated through the result comparisons between model of the Kant composite beam and classical beam theories. Some dynamic phenomena are also observed in the dynamic response analyses of the composite beams subjected to the earthquake excitation and moving load.