Buckling of Stiffened Thin Walled Cylindrical Shells due to Global Shear

Thin walled cylindrical shells are important components of industrial structures such as liquid storage tanks, silos, etc. Shell buckling is usually a major failure mode of thin walled shells under extreme loads such as earthquakes. Longitudinal and radial stiffeners are generally used in order to increase buckling capacity of thin walled shells. During an earthquake, cylindrical shells may experience global shear and suffer shear buckling. Buckling of thin walled shells is highly dependent to imperfections. In this study buckling of imperfect cylindrical stiffened tanks due to global shear and seismic loads are studied. To this end nonlinear FE static analyses have been performed in order to estimate buckling capacity of imperfect cylindrical stiffened tanks due to global shear. Herein cylindrical tanks of a constant height and different height to diameter (H/D) ratios were considered. Different arrangements of stiffeners were considered for each tank. Random patterns of imperfection with moderate imperfection amplitude were considered in all tanks. Design relations have been presented based on the results of numerical analyses. Finally, time history analyses were performed in order to evaluate the validity of suggested design relations for buckling of cylindrical stiffened tanks due to seismic loads.