DETERMINATION OF CRITICAL BUCKLING LOADS OF METAL SILOS

The paper investigates the determination of critical buckling loads in metal silos used for storing bulk materials. Ensuring the stability of thin-walled cylindrical silo structures is essential for the safe operation and reliability of such facilities. Despite the existence of Eurocode design guidelines, practical issues arise due to significant deviations between calculated and actual critical loads, as well as structural imperfections and manufacturing defects that often go unaccounted for in traditional analysis. The study highlights the influence of geometrical parameters such as shell height, diameter, wall thickness, and corrugation depth on the buckling behavior of steel silos. Through the analysis of recent international research, including work by Polish, British, Chinese, and Ukrainian researchers, various destabilizing factors are examined. These include asymmetric material flow during discharge, wind loads on empty or partially filled silos, and defects such as circumferential or meridional cracks. Particular emphasis is placed on eccentric unloading, which can trigger local instabilities in tall, slender silos. To address these issues, the paper applies both numerical and analytical methods, including nonlinear shell theory and variational approaches. The research introduces a model of a silo shell with variable thickness, accounting for stress redistributions and the effects of internal pressure and wind load. Special attention is given to the axial symmetry of deformation and the role of internal structural elements such as stiffeners and ring supports in preventing failure. A significant part of the analysis employs a sixth-order differential equation derived from shell deformation theory, incorporating geometric and material characteristics such as Young’s modulus, Poisson’s ratio, and the structural stiffness of stiffeners. Numerical simulations were used to identify critical stress values under different loading conditions and deformation modes. The results reveal that the presence of internal pressure significantly increases the stability margin by shifting deformation from local dimpling to global axisymmetric buckling modes. The paper concludes that accurate prediction of critical loads requires a comprehensive approach integrating imperfections, load asymmetry, and nonlinear effects. This approach enables more reliable assessment of silo safety, supports the development of improved design standards, and contributes to reducing the risk of structural failures. The findings are relevant for engineers involved in the design, analysis, and maintenance of steel silo structures in industrial and agricultural contexts.