ICE PRESSURES IN LIQUID MANURE TANKS

Cylindrical reinforced concrete tanks are the most common structure us ed for storing liquid manure during the period when land application i s not feasible. In most parts of Canada, ice forms in a liquid manure tank and the wall has to be designed for the radial pressure exerted b y the ice when it expands. The magnitude of the ice load is mainly a f unction of the ice thickness. Godbout and Marquis (1990) have recommen ded a design thickness of 0.5 m for the Quebec City region and an aver age design pressure of 50 kPa over the thickness of the ice layer. Thi s means a design ice load of 25 kN/m of circumference. A subsequent st udy by Carrier et al. (1995) indicates that an ice thickness of 0.16 m would be appropriate for design in southern Ontario. Twenty linear el astic finite element stress analyses of cylindrical tanks were perform ed to determine hoop stresses in the wall from a radial ice load appli ed near the top and at midheight. Design curves are provided for eight tank geometries to allow structural designers of liquid manure tanks to quickly calculate these hoop stresses. After combining these hoop s tresses with those from the manure and other loads, they can be used t o design the wall thickness and the hoop reinforcing steel. A sample c alculation of ice load hoop tension is provided in the Appendix.