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Design loads on the walls of horizontal (bunker) silos are affected by wall slope, silage-wall friction, the way in which the silage is piled up above the top of the wall and the compaction method. Most of these factors are not accounted for in the present Canadian Farm Building Code. Structural problems have been experienced with some very high walls. Based on a three-year study of horizontal silo wall loads, this paper presents simple design formulae which take into account the various factors mentioned earlier. Design wall loading from silage is proposed as an equivalent liquid pressure using a pressure ratio K that is closely related to the "at rest" pressure ratio. For corn silage it is recommended that the value of K be taken as 1.65Ka, where Ka, the active pressure ratio, is based on an internal angle of friction of 29?. The dry matter density, in kg/m , is recom mendedto be 200 plus 4 times the mass, in tonnes, of the vehicle used for compactionof the silage. Based on a six year study carried out by Messer and Hawkins in England it is believed that the same design recommendation is valid for grass. It is also proposed that the design load from a tracked compaction vehicle is a line load equal to Kf times the line load representing one track. This design load is applied anywhere at right angles to the wall surface, 0.5 m below the silage surface, in the most unfavourable location. Similarly, the design load from a wheeled tractor is a point load equal to Kf times the wheel load. For all design loads Kf can be taken as 1.65Ka where Ka is based, for cornsilage, on an internal angleof friction of 29?.
J.C. Jofriet,Q. Zhao and S.C. Negi 1992. DESIGN RECOMMENDATIONS FOR STRUCTURAL LOADS ON HORIZONTAL SILO WALLS. Canadian Agricultural Engineering 34(1):95-104.
Canadian Society for Bioengineering