The new techniques in the building of reinforced concrete structures developed in recent years have made it possible to envisage the design of silos for which the cross-section does not have to be constant. However, the design of such structures requires some knowledge of the stresses exerted by granular material on the side walls of the bin.

Among the new possible shapes, the truncated cone is particularly interesting, as its only difference with traditional structures lies in the slant of its side walls.

Using a group of six truncated-cone-shaped scale models, each having a different slanting angle, and the walls being instrumented with strain gauges, the normal stress was calculated, for a storage of granular material whose rheology is of the rigid-plastic type.

Moreover, the study of the bidimensional ultimate equilibrium of a horizontal layer of supposedly rigid-plastic granular material pressing against the sides, has made it possible to write the theoretical equation of the field of stresses in the walls of truncated-cone-shaped bins.

The study of experimental results shows the decrease of normal stress in truncated-cone-shaped bins, and allows the simple characterization of this decrease according to one parameter only: the conic shape of the silo.

Beside, this study allows future research to be made with bins of gentle conic shape, since a substantial reduction of normal stress can be observed even on gently slanting walls.

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