Asymmetry of model bin wall loads and lateral pressure induced from two- and three-dimensional obstructions attached to the wall

An obstruction attached to the wall of a bin produced by cohesive, moldy grain has been reported as a source of failure in steel bins. A study was conducted to estimate the effect of two-dimensional (plane) and three-dimensional (block) obstructions attached to the corrugated wall in a flat-floor model bin where the lateral wall pressure and vertical wall loads were measured. The model bin was 1.83 m in diameter, 5.75 m high, and filled with soft red winter wheat to a depth of 5.0 m (height-to-diameter ratio h/d of 2.75). The plane obstruction had the form of an annulus segment spanning 60° of the bin wall and a width of 0.154 m (surface area of 7.2% of the bin floor area). A three-dimensional obstruction was shaped as a block with two bases identical to the plane obstruction and a height of 0.5 m. The plane obstruction and the upper base of the block obstruction were attached to the wall at h/d ratios of 1.26, 0.81, and 0.38. Even in conditions of near symmetry during centric loading, wall overturning moments of approximately 1 kNm were observed. The highest wall moment measured was 2.7 kNm at the end of filling with the block attached at h/d of 0.38; the moment with a plane obstruction in the same position was 2.1 kNm. Without an obstruction attached to the wall, the maximum lateral pressure increased 2.5 times relative to the static pressuer compared to an increase of 4 times with an obstruction. The data collected indicated that there are considerable additional loads imposed on a bin due to obstructions that may form during storage that are not considered in the design codes and could approach levels observed during eccentric discharge.