Buckling pressures for metal tanks using a reduced stiffness approach

L. A. GODOY; R. JACA

Lake Buena Vista, Florida

Congreso; ASME International Mechanical Engineering Congress and Exposition; 2009

American Society of Mechanical Engineers

The Reduced Stiffness approach to compute lower bounds to buckling loads in shells has been employed by a number of researchers during the last thirty years as a convenient way to evaluate unstable behavior in imperfection-sensitive shells using simple eigenvalue analysis and without having to perform incremental nonlinear analysis. Recent applications by the authors and other researchers have shown ways to compute lower bounds using finite element analysis, in which a modified eigenvalue analysis is constructed by neglecting the membrane contributions to the matrix containing the initial stresses. This paper illustrates the application of the methodology within the context of finite element analysis to cases of shells with thickness changes in the meridional direction. A special purpose semi-analytical finite element code has been employed for uniform pressures acting on aboveground steel tanks. The tanks are representative of those constructed for the oil industry, with radius to thickness ratios of the order of 1500, and height to radius ratios lower than one. The results illustrate that the membrane contribution should not be completely eliminated in order to obtain lower bounds to buckling pressures and good estimates of buckling modes.