| Thin-walled column-shell structure is a relatively common type of structure in practical engineering,to meet various engineering situations often by different shell strips in different combinations of forms,such as thin-walled flat shell(folded plate)structure and thin-walled cylindrical shell,etc..These complex structures have a wide range of applications in various fields such as aerospace,ships and automobiles,buildings and bridges.The research on the dynamical behavior of thin-walled column-shell structures is often limited to classical boundary conditions,and the solution methods are not uniform;at the same time,the vibration response problem between shell strips is not sufficiently studied,and the use of slender shell strip structures can easily cause a large amount of computational resources to be wasted,and the use of combined structures is not flexible enough.In this paper,the vibration characteristics and response of the thin-walled column-shell structure combined with multiple shell strips are studied more systematically to address the above-mentioned research deficiencies.The main work is as follows:1.The definition of thin-walled column-shell and related assumptions of thin-walled shell vibration theory are introduced,followed by the study of the deformation problem of thin-walled cylindrical shell based on Donnell’s simplified theory of elastic thin shells from the problem of deformation of meshed surfaces,and the general vibration differential control equations of elastic thin shells are established through the shell stress-strain relationship.It lays a theoretical foundation for the subsequent study of the vibration of thin-walled cylindrical shell structures with the improved finite strip method.2.The improved Fourier series method is introduced into the semi-analytic element method to establish the improved finite strip method for solving the vibration analysis calculations of thin-walled column-shell structures.The improved Fourier series reduces the dependence on boundary conditions,and will not produce singular matrix in the process of programming numerical calculation,which will seriously affect the accuracy of calculation results;The semi analytical method is especially suitable for slender shell strip structures,which solves the problem of waste of resources caused by other calculation methods.The improved finite strip method still takes the displacement of the surface in the structure as the reference,and the displacement tolerance function contains the Chebyshev polynomials of the first type in the circumferential discrete direction and the improved Fourier series in the axial continuous direction,and the kinetic energy,the deformation energy and the spring potential energy stored in the boundary spring exist in the system are expressed by the displacement tolerance function through the Hamilton energy principle,and the partial derivatives of the unknown Fourier coefficients are obtained by extracting the unknown The Fourier coefficients are biased,the stiffness and mass matrices of the structure are extracted,and the inherent frequency and velocity response of the thin-walled column-shell structure under different elastic boundary conditions are obtained by solving the eigenvalues and eigenvectors of the combined matrix.Finally,the calculation results are compared with the simulation results of commercial finite element software ABAQUS,which verifies the accuracy of the method in this paper.3.A more systematic study of the dynamic properties of thin-walled column-shell structures is carried out based on the modified finite strip method.The order frequencies of the structure are calculated under different classical and elastic boundary conditions;the effects of various parameters(including the opening angle of the structure,the number of shell bars used to form the structure,the length-to-diameter ratio(l/R)and the thickness-to-diameter ratio(R/h)of the structure,etc.)on the order frequencies and vibration response of the structure are investigated. |
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