Grain Storage Systems Design

This chapter focuses on the various factors that influence the design of grain storage systems. Agricultural grains are free flowing bulk materials and cohesion is usually not taken into account in structural designs. Grains can develop cohesion when improperly stored or handled, particularly under high moisture conditions when mold develops. Storage and handling facilities for agricultural grains are designed based on the assumption that grain will be free flowing. Agricultural grains are free flowing if they have been dried to safe storage moisture contents. The proper operation of harvesting, cleaning, and drying processes is essential to maintain grain in a free flowing condition. The dust produced by agricultural grains consists of starch particles, which when suspended in air under low humidity conditions, are explosive. Wheat, corn, and soybean dust are dangerously explosive under dry conditions. Proper wiring to avoid sparks and in some cases the use of brass tools to avoid sparks are some of important factors considered during the design of grain storage facilities. Loads caused by external environmental effects include loads caused by wind, snow, rain, and earthquake. The normal design factors dictated by the design codes and standards that take into account these environmental load effects also apply to grain bins and grain storage buildings. Many grain bins have conical roofs with roof slopes only slightly larger than the 28°, the angle of repose of the storage grain. The bins are unheated and are normally made from galvanized steel, which can be considered as a slippery surface. Using these general criteria, the roof snow loads for these types of structures can be approximately 75 to 80% of the ground snow load.