A simplified analytical procedure for assessing the worst patch load location on circular steel silos with corrugated walls

Silos are widely used in the food and chemical industries for the storage of granular materials. The calculation of their wall dimensions is complicated since the interaction between the stored material and that from which the silo is made is complex, a consequence of their very different mechanical behaviours. The loads exerted on the silo walls by stored materials must be taken into account in silo design, and the means for calculating them is contemplated in Eurocode EN 1991-4. The complexity of the phenomena that occur within silos often leads to the appearance of unexpected and asymmetrically distributed pressures. This is taken into account in the above Eurocode via the concept of the patch load, which is asymmetric and can be exerted at any point on the silo wall. A finite element model has been developed in order to check that the stress resultants derived from the patch load on steel silos with corrugated walls may be predicted by using the well-known expressions of shell theory. Then, a simplified analytical procedure has been developed for predicting the worst location of patch loads for all metal silos, but with special application to corrugated steel silos in Action Assessment Class 3. It has been found that significant differences may be found for most cases with the worst location for the patch load defined in Eurocode for welded silos in Action Assessment Class 2. On the other hand, the values obtained for the maximum meridional membrane stress resultant do not significantly differ, except for high slenderness values in intermediate slenderness silos.