Effects of patch loads on structural behavior of circular flat-bottomed steel silos

Abstract

The present paper investigates the structural behavior of circular steel silos subject to patch loads. For reference purposes, first the patch loads are assumed to be in two squares that are in generally accordance to silo loading codes [DIN 1055. Design loads for buildings. DIN 1055 Part 6, Deutsches Institute fur Normung, Berlin; May 1987; Bases for design of structures—loads due to bulk materials. ISO11697; 1995]. The investigations reveal that the patch loads have a great effect on the stress states in the silo from the linear elastic analysis (LA). Geometrical non-linearity and primary pressures have beneficial effect. Fourier decompositions of the two square-shaped patch loads show that the effect of the shape of patch loads depends not only on the harmonic index, but also on particular stress component. For a pressure with a lower harmonic index (e.g. cos θ, cos 2 θ), only limited effect was observed for all stress components. A pressure with medium-sized harmonic index (cos 4 θ, cos 6 θ) has a great effect on meridional compressive stress, while for higher harmonic index; the effect was significant for von Mises equivalent stress. Buckling analyses with geometrical non-linearity and material non-linearity taken into account show that the effect of patch loads could be covered by a certain percentage increase of the vertical frictions, if the patch load approach were adequate to represent the non-uniformity of wall pressures in circular flat-bottomed steel silos.