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FROM:
Medhanye B. Tekleab, “Buckling of thin-walled cylindrical and conical metal tanks: Analysis, test evaluation and design”, Ph.D. dissertation, Civil Engineering Sciences, Graz University of Technology, 2009
ABSTRACT: This work researches the stability of cylindrical and conical thin-walled tank shells from the basic level in view of both analysis and previous test results. Detailed discussions on failure modes, numerical simulations and re-investigation of test results have been made. The axisymmetric elastic-plastic buckling phenomena, buckling modes and strengths of meridionally compressed and internally pressurized perfect and imperfect cylindrical and conical shells have been investigated in detail. The effects of imperfection wavelength, location along the meridian, orientation, and amplitude of sinusoidal & local imperfections have been thoroughly studied. The worst possible combined effect of an edge restraint and an imperfection in destabilizing such shells has also been discussed. All results are represented and interpreted in such a way that they can easily be understood and used for design purposes. Simplified expressions are obtained for the prediction of axisymmetric elastic-plastic buckling strength of general thin-walled cylindrical and conical shells under the mentioned loading situations. Design recommendations have been proposed. Comparisons with and critical review of few previous research works have as well been thoroughly carried out.
Detailed investigation of the numerous Gent laboratory test results (obtained about 30 years ago at the Laboratory of Model Testing at Gent University, Belgium) on liquid-filled conical shells, shortly called LFC, that have been made in response to a structural disaster in Belgium along with detailed discussions, explanations, and conclusions have been done. Previous LFC-related research works on nonlinear simulation of liquid-filled conical shells with and without geometric imperfections have as well been discussed and few cases have been re-examined for confirmation and further studying purposes. Relevant explanations and conclusions have been given to the outcomes of those works. Moreover, the Belgium (1972) and Canada (1990) steel water tower failure cases have been carefully examined to check and compare their elastic buckling strengths with the applied loads during failure; and to check for any possible roles played by plasticity effects during the collapse. Previous research works related to the collapse of the water towers have also been discussed. The notion of a “corresponding cylinder” of a liquid-filled conical shell has been introduced which behaves in exactly the same way as the LFC. Detailed and comprehensive investigation of this “corresponding cylinder” was then made with the simple outcome that the liquid-filled cone behaves like a “wet cylinder”, i.e. with respect to its axisymmetric deformation and buckling behavior.
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