Buckling Analysis And Optimization Design Of Thin-walled Stiffened Structures

Thin-walled structures are widely used in engineering and practice. With lessmaterial used, the structure has a larger carrying capacity. Thin-walled structures tendto be instability before strength failure when being loaded. Reinforce thin-walledstructure with ribs could improve structural buckling bearing capacity effectively.Based on linear buckling theory and nonlinear buckling theory, the buckling analysisand optimization design of stiffened plate and stiffened cylindrical shell are studiedthrough finite element method. The main contents are included as follows:(1) Based on the finite element analysis technology and Evolutionary StructuralOptimization method ideology, an optimization strategy for thin-walled plate whichcan be easily carried out is proposed and a ribs layout optimum model is built."Influence degree" of unit is created for replacing the sensitivity of units. Thecompute of "influence degree" of structural unit and the process of topology optimumwork are realized by the finite element analysis software. In the ribs layout study,stiffened plate subjected to in-plane loading is optimized for getting its largestbuckling bearing capacity. Ribs layout optimum solutions of stiffened plate under avariety of loads are obtained.(2) The optimization model of thin-walled stiffened cylindrical shell which hasa constant volume is developed and solved. The objective function ofthe optimizationmodel is the maximum buckling bearing capacity and the design variables include thenumber of stiffeners, the skin thickness and the section sizes of stiffeners. Thestructural optimization process is set up and solved by combination of ISIGHT MIGAand ANSYS APDL.(3) Considering geometric nonlinear and material nonlinear, nonlinear bucklinganalyses of different ribs’ number stiffened cylindrical shell which are subjected toaxial pressure with initial geometric imperfection are studied. Compared with linearand nonlinear buckling analyses, optimum solution with linear buckling analyses isnot the maximum buckling load value of the overall structure. Nonlinear bucklingbearing capacity of the stiffened cylindrical shell which has the largest linear bucklingcapacity is not the largest.