In Fig. 3, the cause for this peak is the wedge shown in
black, which is acting on the passive reacting bulk within the
conical part of the hopper. For mass flow silos, the stress peak
is supposed to remain at the junction, while for semi mass
flow silos it is believed to move further upward. The
uncertainty of its magnitude and distribution is also reflected
in the different handling in the international codes. As an
example, the patch pressures according to DIN 1055 part 6 [3],
Euro Code (EC) 1 part 4 [4]; While the German and the EC1
code recommend “switch” patch pressures only for mass flow
silos at the junction of the vertical and inclined wall, the
Australian guidelines also include a force varying in height
for the cylindrical part of the silo corresponding to the
pressures occurring in semi-mass flow situations, [5].
From the mentioned before it can be clearly seen that more
accurate methods to determine the relevant loads due to bulk
materials are urgently needed. A numerical simulation seems
to be an appropriate method to get a better understanding of
granular flow and the relevant phenomena. Experiments are
very time consuming, difficult to conduct and only the
reaction and not the behavior of the bulk material within the
bin can be studied.
Finite Element simulations of granular flow in silos based
on a continuum approach are becoming more and more
popular due to the increasing computer power and the
capacity of the available program in the last decades.
Nevertheless it must be recognized, that the simulation of
granular flow in silos is still a demanding task. Some aspects
will be discussed in the following.