Structural loads on bunker silo walls: Numerical study

Abstract

The finite element method (FEM) of analysis was used to investigate wall pressures exerted by silage on bunker silo walls. Normal wall pressures determined by FEM analysis were in very good agreement with experimental values obtained in a field experiment on a large bunker silo. Both experimental and numerical results show that silage pressure increases linearly with depth and that an equivalent liquid pressure formula can be used for prediction. The density of the equivalent liquid can be calculated as the product of the silage bulk density and the pressure ratio (the ratio of the normal to vertical pressure). The pressure ratio is dependent on wall slope, silage surcharge angle and friction angle between wall surface and silage material. The pressure ratio increases by about 45% when the wall slope changes from 90 to 75 °, and by as much as 70% when the surcharge angle changes from 0 to 20 °. It is recommended that both the surcharge angle and the wall slope be taken into account in the design of bunker silos. Wall-silage friction reduces the pressure ratio by about 10% when the coefficient of friction increases from zero to 0·4. The effect of wall-silage friction is therefore of less importance in design calculations.