Buckling behaviors and simplified design method for steel silos under locally distributed axial load

Buckling behaviors of steel silos subjected to locally distributed axial load (LDAL) were studied by a Finite Element Model (FEM), which was verified by available test and analytical results. Studied parameters included the internal pressure, the Local edge load Center Angle (LCA) and the radius-to-thickness ratio (R/t) of a silo. Buckling modes, distributions of reaction forces along the silo bottom edge and buckling stresses were presented. FEM simulations showed that a compression arch was formed on the silo wall to transfer the LDAL to boundaries; and between the feet of compression arch the reaction was in tension. The span and the height of the compression arch almost did not change with the varying of LCA for silos having the same internal pressure and R/t. However, the height of the compression arch decreased with the increase in internal pressure. A silo under LDAL was more likely failed by elastic buckling when the internal pressure was at low level; and at this circumstance the buckling stress increased with the increase in internal pressure. At high level of internal pressure, buckling failure modes of a silo under LDAL changed from elastic buckling to elastic-plastic buckling; and the buckling stress decreased with the increase in internal pressure. For silos with same internal pressure and R/t, the buckling stress decreased with the increase in LCA. Design equations in EC3-4-1 could overestimate the buckling stress of steel silos under combination of internal pressure and LDAL. Based on parameter study results, a practical design equation was proposed for calculating the buckling stress of a steel silo under combined internal pressure and LDAL. Buckling stresses predicted by the proposed equation agreed well with those obtained by FEM.