Simplified method for filling and discharge

1) For silos, where dc is less than 5m a simplified method for considering filling and discharge processes may be applied. In this procedure, the patch loads according to 5.2.1 and 5.2.2 may be adjusted by increasing the horizontal pressures.

2) For concrete silos, silos with stiffeners and silos with non circular cross-sections shapes the increased horizontal pressures for filling (Phf,s) and discharge (Phe,s) are:

where:

Phf is calculated from expression (5.3) Phe is calculated from expression (5.21) b is calcuated from expressions (5.9) or (5.25)

3) For thin walled circular silos, the increased horizontal pressures for filling Phf,s and discharge Phe,s and the increased vertical pressure for fillingpwf,s and discharge pwes are:

where:

phf,s

Phe pwf,s pwe b is calculated from expression (5.3) is calculated from expression (5.21) is calculated from expression (5.2) is calculated from expression (5.20) is calculated from expressions (5.9) or (5.25)

5.3 Squat silos

1) Wall loads in squat silos should be calculated as for slender silos (see 5.2) with the modifications for the load magnifiers, the patch pressure, the horizontal pressures, and the bottom loads.

2) The modifications concerning the load magnifiers Ch and Cw and the patch pressure are: For silos where:

p,sq

where:

3) The modifications shown for lateral pressure is shown in Figure 5.4. The lateral pressure Ph at the point at which the upper surface of the stored material meets the silo wall may be reduced to zero. Below this point, a linear pressure variation may be assumed (Figure 4.4), calculated using in Ks = 1.0, until this linear pressure meets the pressure determined from equation 5.3 or equation 5.21 as appropriate.

4) The vertical pressures Pvf,sq during filling and discharge acting on the flat bottom is:

Pvf, sq = Cb (Pv1 + (Pv2 -Pv3) (1,5 D - h)/(1,5 D - h1) (5.37)

where: Pv1 Pv2

Cb is obtained from expression (5.4) with z = h is obtained from pv2 = g h2

is obtained from expression (5.4) and z = h^see Figure 5.4)

lowest point of the wall not in contact with the stored material (Figure 5.4).

is calculated from expression (5.14)

5) Hopper loads during filling shall be calculated using expression (5.15)

6) Hopper loads during discharge shall be calculated using the guidance given in 5.2.2.2 for flatt bottoms and hoppers.

5.4 Homogenizing silos and silos with a high filling velocity

1)P Homogenizing silos and silos with a high filling velocity shall be designed for the following load cases:

— The stored material fluidised.

— The stored material not fluidised.

— The stored material not fluidised.

2)P In silos storing powders where the velocity of the rising surface of the stored material exceeds 10 m/h it is assumed that the stored material is fluidised.

3)P The pressure on the silo walls p from fiuidised materials shall be calculated as follows:

where:

g1 is the fluidised density.

4) The fluidised density of powders gi may be taken as equal to:

where:

g is the bulk weight density of the powder determined from section 7.

5)P Design loads when the stored material is not fluidised shall be calculated for for slender silos according to section 5.2 and for squat silos according to section 5.3.

Bulk Material Density Method
Figure 5.4 — Wall loads and flat bottom loads in squat silos
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