Finite element analysis of wall pressure in imperfect silos

It is generally accepted that the pressures exerted by stored bulk solid on silo walls after filling are closely predicted by the Janssen theory. However, recent experimental observations of silo wall pressure have shown significant deviations from Janssen pressures even after careful symmetrical filling. Both meridional and circumferential variations from the Janssen values have been found, which induce bending of the wall in reinforced concrete silos and high membrane stresses in steel silos. It has been suggested that the presence of geometric imperfections in the silo wall is a likely cause of these pressure variations. However, no rigorous investigation of the effects of uneven surface profile on wall pressures appears to have been performed, though some simple calculations have been produced. This paper presents a finite element study of the effects of a local axisymmetric wall imperfection on pressures acting on the wall of a circular silo. The effects of imperfection height and imperfection geometry on wall pressures are also investigated. (C) 1997 Elsevier Science Ltd.