Numerical Study On Composite Sandwich Thin-walled Bar With Closed Section

Owing to the characteristics of high intensity ratio,high modulus ratio and light weight,composite structures have been applied abroad in many fields such as aerospace, chemical and civil engineering.Thin-walled bar is an important structure form when they are applied and has more and more wider applications.Furthermore,it will be one main form of composite bridge component in future.In this thesis,a general theoretical analysis method of composite thin-walled bar is presented to aim at the computation of composite sandwich box girder with application to bridge structure.On the basis,the thesis establishes a numerical calculation method of composite sandwich thin-walled bar,Namely,numerical solution of the theoretic equation is accomplish by MATLAB which is a big electro-computer assistant designed software.Firstly,the dissertation makes some supplements and perfections for the calculation theory of composite thin-walled bar(composite thin-walled box girder) which documents[1～4]had put forward.Cylindrical shell theory with no bending moment is employed to analyze their mechanical behavior;the general constituitive equations are presented.Based on the principal minimum potential energy,the governing equations of equilibrium as well as all boundary conditions concerned have been deduced.In addition,a solution to this issue is discussed.Secondly,a combination model of inner,outer surface and core which is in the accordance with the composite thin-walled theory has been set up.The deformations of these three layers are described;the constitutive relationships are introduced;then the general potential energy function is determinate.Based on the principal minimum potential energy,the composite sandwich thin-walled bar's governing equations of equilibrium as well as all boundary conditions concerned have been deduced from the equivalent constitutive equations and general potential energy function.Moreover,the stiffness matrix of equivalent constitutive equations of composite sandwich thin-walled box girder is calculated particularly in need of engineering.The decoupling and solution to the governing equations are discussed comprehensively.The theoretical results of specific issue are obtained at large.Thirdly,the numerical methods of balance governing equation have been studied using Thin-walled bar theory,Composite thin-walled bar theory and Composite sandwich thin-walled bar theory so you say.This solution of equation is accomplished by Matlab which is a high performance numerical calculation and visible software in order to find numerical solutions of the extent and bend of composite sandwich box girder.Furthermore those have been applied in actual engineering.At last,the layer stress analyses of rectangular composite sandwich thin-walled box girder analyzed under the deformations of axial tension and bending by use of the user-defined Matlab programme,what's more,the own programme is debugged and corrected with comparatively analyses of calculation result of the own program.