SUMMARYIn general, shell structural problems can be identiÿed to fall into one of the categories of membranedominated, bending-dominated and mixed shell problems. The asymptotic behaviour with a well-deÿned load-scaling factor shows distinctly into which category a given shell problem falls. The objective of this paper is to present a shell problem and its solution for which there is no convergence to a well-deÿned load-scaling factor as the thickness of the shell decreases. Such shells are unduly sensitive in their behaviour because the ratio of membrane to bending energy stored changes signiÿcantly and indeed can uctuate with changes in shell thickness. We brie y review the di erent asymptotic behaviours that shell problems can display, and then present the speciÿc problem considered and its numerical solution using ÿnite element analysis.

SUMMARYThis paper presents a complete formulation for three-dimensional hydrodynamic analysis of floating flexible structures subjected to surface regular waves, as well as other excitation forces, by employing a direct tight coupling method. The continuum mechanics-based finite element method is employed to model floating structures with arbitrary geometries, which can account for the geometric nonlinearities and initial stress effects that result from the hydrostatic analysis, whereas the boundary element method is used for the fluid via total potential formulation. The simplicity and generality of the present formulation are revealed as compared with the conventional formulation. Numerical examples demonstrate the general capability of the formulation proposed.

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