Advances of thin shell finite elements and some applications—version I

: This report provides an evaluation of dynamic sloshing loads in slack LNG cargo tanks. A comprehensive review of worldwide scale model sloshing data is presented. The data are reduced to a common format for the purposes of defining design load coefficients. LNG tank structural details are reviewed with emphasis placed on defining unique design features which must be considered in designing LNG tanks to withstand dynamic sloshing loads. Additional scale model laboratory experiments are conducted to supplement the available model sloshing data. Experiments are conducted in combined degrees of freedom to establish the potential for multi-degree of freedom excitation for augmenting dynamic sloshing loads. Experiments are also conducted to establish the sloshing dynamic pressure-time histories which are necessary for structural response analysis. Experiments are also conducted on representative segments of a full-scale LNG ship tank structure which is loaded with a typical full-scale dynamic sloshing pressure as predicted from the model results. Analytical studies are undertaken to provide techniques for determining wall structural response to dynamic slosh loads. Finally, design methodology is presented for membrane and semi-membrane tanks, gravity tanks, and pressure tanks whereby the design procedures sequences from comparing resonant sloshing periods to ship periods, defining the design loads, and designing the tank structures affected by dynamic slosh loads by delineated procedures which vary with tank type.

Evaluation of liquid dynamic loads in slack lng cargo tanks

Postbuckling analysis of elastic shells of revolution considering mode switching and interaction

The imperfection sensitivity of thin shells of revolution has been a topic of great interest to researchers and designers. With the gradual emergence of the new approach of structural design based on advanced numerical simulation, the efficient and accurate prediction of the behaviour of imperfect shells has recently assumed new significance. This paper first presents an efficient semi-analytical finite element formulation for the nonlinear analysis of imperfect shells of revolution subject to general nonsymmetric loads. Both the applied loads and the initial geometric imperfections may take any form and are approximated by Fourier series expansions. Application of the analysis to study the effects of geometric imperfections on the behaviour of shells of revolution is then presented to demonstrate the accuracy and capability of the present method and the imperfection sensitivity of shell structures. As a special case of the present formulation, two different approaches are also presented for the postbuckling analysis of perfect thin shells of revolution under axisymmetric loads. The accuracy and capability of both methods are demonstrated using a number of numerical examples, which also allows some new insight to be gained into the postbuckling behaviour of perfect shells of revolution.

V.M. Trbojevic

Papers

Thin shell finite element by the mixed method formulation — Parts 2 and 3

Thin shell finite element by the mixed method formulation — part 1