Buckling of Cylindrical Shells with a Granular Core Under Global Bending: Strength Gains and Imperfection Sensitivity

Abstract

Thin cylindrical shells are commonly employed in civil and structural applications in which the dominant loading condition is global bending. In applications such as wind turbine towers and offshore piles, the design of the structure is commonly limited by buckling. The traditional approach to improving buckling strength pursuant of greater design economy is to use steel ring and/or axial stiffeners. However, the total steel tonnage may be reduced with stiffeners, but the additional fabrication costs can limit the cost advantage.Meanwhile, it has long been observed in the silo industry that granular filled cylinders exhibit strength gains due to the internal pressure and stiffness of the granular bulk solid against the shell wall. For large diameter fabricated steel tubes in bending, an elastic granular fill may be useful in replacing ring stiffeners, increasing critical buckling moments, and reducing risk by providing more stable postbuckling behaviour. However, the strength gains related to the elastic stiffness of a granular core has received very little attention and has been limited to the axial loading condition.In the project work, the candidate uses theoretical and computational methods to investigate the effects of an elastic granular fill on the buckling strength of cylindrical shells subject to global bending. In particular, cylinders in the elastic-plastic range will be considered in order to represent applications such as wind turbine towers and offshore piles. Effects of an elastic bulk fill on strength gains and imperfection sensitivity are considered with interest in improving design economy.