Vertical Loads Due to Wheat on Obstructions Located on the Floor of a Model Bin

Abstract

Tests were conducted in a model grain bin to evaluate the vertical loads acting on differently shaped obstructions embedded in wheat during filling, detention, and discharge. The bin had corrugated galvanized steel walls with a 1.83 m diameter and a flat bottom. All tests were conducted in a bin that was centrically loaded and unloaded. Three differently shaped obstructions (disc, cone, and cylinder) were tested; each had a circular base equivalent to 6% of the bin floor area. The obstructions were supported in the bin using a three-legged support structure. Each leg of the support structure rested on a load cell attached to the bin floor. Tests were conducted with the obstructions located in the bin at three different eccentricity ratios (ratio of the centerline of the obstruction to the bin radius, ER = 0, 0.5, and 0.67) and at two different grain heights (height of grain depth to bin diameter ratio, H/D = 0.4 and 0.75). The radial distribution of vertical pressures in the bin varied, with the highest pressure in the center of the bin and the lowest at the bin wall. The largest vertical load on the disc and cone obstructions was measured at the end of filling. The largest load on the cylindrical obstruction was observed immediately after the initiation of bin discharge. At the end of filling and detention, the vertical loads on the disc, cone, and cylinder were 4.8, 3.7, and 4.9 kN, respectively, for obstructions located at ER = 0 and H/D = 0.4. At a location closest to the bin wall (ER = 0.67), the vertical loading on the disc, cone, and cylinder were 4.4, 3.4, and 4.4 kN, respectively. The greatest difference in vertical loading between the location and type of obstruction was on the order of 50%. Bending moments were also observed to act on these obstructions. Bending moments at ER = 0.67 were much larger than those determined at ER = 0.5. For the disc and cone, moments at ER = 0.67 were three times as large as those determined for tests conducted at ER = 0.0. At the onset of discharge, the vertical loading on both the disc and cone decreased significantly, while the vertical loading on the cylinder increased significantly. Recommendations based on Eurocode I were used to predict the vertical loading on the disc and cylinder embedded in grain. This technique did an adequate job of predicting the maximum loading on both obstructions within the bin; however, it did not take into account the effect of unloading on the obstruction forces.