In Lieu of an Introduction

Thin shells are often the best and only choice for designers of flying vehicles, naval vehicles and civil engineering structures. Shell behaviour under a growing load demonstrates its essential nonlinearity, manifesting itself in buckling, in a variety of postbuckling shapes, and in rapid transitions from one shape to another. Nonuniformity of shell structure and loading appeared to be the key factors influencing shell instability (that is the possibility for rapid change of deformed shape, for development of large deflections). The classical Euler approach to stability analysis presumes an ideal undeformed initial state and considers possibility of the solution non-uniqueness in its small vicinity, narrowing the scope of analysis and often delivering improper critical loads. Full nonlinear analysis and its efficient numerical implementation are needed for an investigation of shell behaviour. Typical shell behaviour patterns are studied and the complicated branching of the respective nonlinear boundary problems (including primary, secondary, and tertiary bifurcation paths) are revealed and analyzed. Such important factors as nonuniformity of load and structure (non-symmetric load pattern, structural defects and imperfections, anisotropy, etc.) are to be studied as the causes of initially nonlinear behaviour, transformations of stress-strain state during shell uploading, and a variety of postbuckling forms. Such analysis is performed on the basis of wide-scale numerical analysis. The technical progress of recent decades has placed before designers the paramount task of perceiving complicated loads for structures with minimal structural weight. For aerospace and naval vehicles, as well as civil engineering structures, thin shells, mostly cylindrical and spherical, have been accepted as the best solutions.