Buckling of shells - Pitfall for designers

Abstract

Purpose I order to produce efficient, reliable designs and to avoid unexpected catastrophic failure of structures of which thin shells are important components, the engineer must understand the physics of shell buckling. The objective of this survey is to convey to the reader a feel for shell buckling, whether it be due to nonlinear collapse, bifurcation buckling, or a combination of these modes. This intuitive understanding of instability is communicated by a large number of examples involving practical shell structures which may be stiffened, segmented, or branched and which have complex wall constructions. With such intuitive knowledge the engineer will have an improved ability to foresee situations in which buckling might occur and to modify a design to avoid it. He will be able to set up more appropriate models for tests and analytical predictions. The emphasis here is not on the development of equations for the prediction of instability. For such material the reader is referred to the book by Brush and Almroth. n Emphasis is given here to nonlinear behavior caused by a combination of large deflections and plasticity. Also illustrated are stress redistribution effects, stiffener and loadpath eccentricity effects, local vs general instability, imperfection sensitivity, and modal interaction in optimized structures. Scattered throughout the text are tips on modeling for computerized analysis. The survey is divided into nine major sections describing: 1) several examples of catastrophic failure of expensive shell structures; 2) the basics of buckling behavior; 3) classical buckling and imperfection sensitivity; 4) nonlinear collapse and the appropriateness of linear bifurcation buckling analyses for general shells; 5) bifurcation buckling with significant nonlinear prebuckling behavior; 6) effects of boundary conditions, load eccentricity, transverse shear deformation, and stable postbuckling behavior; 7) optimization of buckling-critical structures with consequent modal interaction; 8) a suggested design method for axially compressed cylinders with stiffeners, internal pressure, or other special characteristics; and 9) two examples in which sophisticated buckling analyses are required in order to derive improved designs. The paper focuses on static buckling problems.