Elastic Buckling of Imperfect Cylinders Containing Granular Solids

Abstract

Metal silos are subject to both internal pressure and axial compressive stresses in their cylindrical-shell walls. Their design is often controlled by buckling. The buckling strength is greatly reduced by geometric imperfections in the wall, but increased by internal pressure. It is also increased by the stiffness of a granular bulk solid against the wall. This stiffness provides a restraint to the lower parts of funnel-flow-silo walls. This paper examines the elastic buckling strengths of imperfect cylindrical shells under axial compression, with imperfections in the form of a depression at a circumferential welded joint. The effects internal pressure and elastic restraint from the static stored solid are examined. A procedure by which the characteristics of the granular solid may be incorporated into the buckling calculation is proposed. The restraint stiffness is taken to be dependent on the stress level in the stored solid, the mode of buckling, and the level of internal pressure. The results may be used in planning experiments to verify the theory, or in any assessment of the probable strength of an existing structure.