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The design of cylindrical nonprestressedcon crete storage structures does not appear to be governed by any building code in Canada. Consequently, design practices for farm tower silos vary from province to province, and indeed from builder to builder. This paper is concerned with the selection of the wall thickness and the hoop reinforcement for bottom-unloading silos. The major loads, lateral silage pressure, temperature, shrinkage and creep are discussed in detail. This is followed by recommendations on the internal hoop forces and stresses caused by these loads. For the lateral silage pres sure this includes recommendations for calculating the hoop tension and bending moments in the vicinity of the unloader where large over pressures occur. Temperature stresses are given in terms of the tem perature gradient in the wall and suggestions are made for estimating shrinkage and creep stresses. Wind, earthquake and self-weight of the silo and equipment are not considered in this paper. Three design criteria are presented. The first limits the circumferential tensile stress in the concrete wall from lateral pressure, shrinkage and temperature gradients. The second is concerned with the tension in the hoop rein forcement and guards against collapse. The third limits the crack width of the cracked concrete section. Reasonable load combination factors have been recommended for the tensile concrete stress design criteria which must be investigated for four different loads. Recommendations on the tensile strength of concrete and on appropriate strength factors have been made.
J.C. Jofriet 1989. BOTTOM-UNLOADING CONCRETE SILO WALL DESIGN. Canadian Agricultural Engineering 31(1):73-79.
Canadian Society for Bioengineering