51989151-DIN-1055-6-2005Silos
Transcript of 51989151-DIN-1055-6-2005Silos
-
DIN 1055-6:2005-03
CONTENTS Page
Foreword 7
1 scope 8
2 references to other standards 10
3 terms and symbols 11
3.1 terms 11
3.2 symbols 15
3.2.1 General 15
3.2.3 Latin letters, capital 15
3.2.3 Latin letters, small 17
3.2.4 Greek letters, capital 20
3.2.5 Greek letters, small 20
4 illustration and classification of actions 21
4.1 illustration of action in silos 21
5.6 principles of calculations for explosions 30
6 bulk material parameters 31
6.1 general 31
6.2 bulk material parameters 32
6.2.1 General 32
6.2.2 Determination of bulk material parameters 34
6.2.3 Simplified procedure 35
6.3 measurement of bulk material parameters in tests 35
6.3.1 Experimental determination 35
6.3.2 Bulk material density, 36 6.3.3 Coefficients of wall friction 36 6.3.4 Angle of inner friction, i 36 6.3.5 Horizontal load ration,K 37
1
-
DIN 1055-6:2005-03
6.3.6 Cohesiveness, 37 C
6.3.7 Bulk material correction value for the reference-surface load 37 opC
7 loads on vertical silo walls 38
7.1 general 38
7.2 slim silos 39
7.2.1 Fill loads on vertical silo walls 39
7.2.2 Discharge loads on vertical walls 44
7.2.3 Uniform increase of loads in place of reference-surface loads for fills and
discharges of the load-types for circular silos 49
7.2.4 Discharge loads for circular silos with large eccentricities during discharge 50
7.3 low silos and silos of medium slimness 55
7.3.1 Fill loads on the vertical walls
7.3.2 Discharge loads on the vertical walls 57
7.3.3 Large eccentricities for filling in of circular low silos and circular silos
of medium slimness 59
7.3.4 large discharge eccentricities for filling in of circular low silos and
Circular silos of medium slimness 60
7.4 silos with braced walls 61
7.4.1 Fill loads on vertical walls 61
7.4.2 Discharge loads on vertical walls 62
7.5 silos with fluidized bulk material 62
7.5.1 General 62
7.5.2 Loads in silos for storage of fluidized bulk material 62
7.6 temperature differences between bulk material and silo structure 63
7.6.1 general 63
7.6.2 loads due to a decrease in the surrounding atmospheric temperature 64
7.6.3 loads due to filling-in of hot bulk materials 64
7.7 loads in rectangular silos 65
7.7.1 Rectangular silos 65
7.7.2 Silos with internal braces 65
8 loads in silo hoppers and silo bottoms 65
2
-
DIN 1055-6:2005-03
8.1 general 65
8.1.1 Physical parameters 65
8.1.2 General rules 67
8.2 horizontal silo bottoms 69
8.2.1 Vertical loads on horizontal silo bottoms in slim silos 69
8.2.2 Vertical loads on level silo bottoms in low silos and silos of
Medium slimness 69
8.3 steep hoppers 71
8.3.1 Mobilized friction 71
8.3.2 Fill loads 71
8.3.3 Discharge loads 71
8.4 flat hoppers 72
8.4.1 Mobilized friction 72
8.4.2 Fill loads 73
8.4.3 Discharge loads 73
8.5 hopper loads in silos with air-injection equipment 73
9 loads on tanks 74
9.1 general 74
9.2 loads due to stored fluids 74
9.3 parameters for fluids 74
9.4 suction loads due to insufficient aeration 74
Annex A (informative) Basis for the Planning of Structures
Rules that complement DIN 1055-100 for silos and tanks 75
A.1 general 75
A.2 border limit for load capacity 75
A.2.1 part-safety correction value 75
A.2.2 Actions on structures - Actions in silos and tanks correction value
75
A.4 conditions for calculation and action-combinations for the
Requirement categories 2 and 3 76
3
-
DIN 1055-6:2005-03
A.5 action-combinations for the
Requirement category 1 77
Annex B (normative) Actions, Part-Safety Factors and Composite
Correction Values for the actions on tanks 78
B.1 general 78
B.2 actions 78
B.2.1 loads from stored fluids 78
B.2.2 loads from internal pressures 78
B.2.3 loads from temperature changes 78
B.2.4 intrinsic loads 78
B.2.5 loads from insulation 78
B.2.6 distributed working loads 79
B.2.7 concentric working loads 79
B.2.8 snow 79
B.2.9 wind 79
B.2.10 low pressure due to insufficient aeration 81
B.2.11 seismic loads 81
B.2.12 loads due to connecting structures 81
B.2.13 loads due to non-uniform settlement 81
B.2.14 catastrophic loads 81
B.3 part-safety correction values for actions 81
B.4 combination of actions 81
Annex C (normative) measurement of bulk material parameters for
Determination of silo loads 82
C.1 general 82
C.2 application 82
C.3 symbols 82
C.4 terms 83
C.5 taking of specimens and their preparation 83
4
-
DIN 1055-6:2005-03
C.6 determination of bulk material density 84 C.6.1 short description 84
C.6.2 test apparatus 84
C.6.3 process / procedure 85
C.7 wall friction 85
C.7.1 general 85
C.7.2 co-efficient of wall friction m for the determination of loads 86 C.7.3 angle of wall friction wh for examining the flow behaviour 87 C.8 horizontal load ratio K 88
C.8.1 direct measurement 88
C.8.2 indirect measurement 89
C.9 stability parameters: cohesiveness c and angle of internal friction i 89 C.9.1 direct measurement 89
C.9.2 indirect measurement 91
C.10 effective elasticity module Es 93
C.10.1 direct measurement 93
C.10.2 indirect measurement 95
C.11 determination of the upper and lower characteristic values for the bulk
Material parameters and the determination of the conversion factor a 96
C.11.1 testing principle 96
C.11.2 assessment methods 97
Annex D (normative) assessment of bulk material parameters for determination
Of silo loads 99
D.1 goal 99
D.2 assessment of the wall friction co-efficient for a corrugated wall 99
D.3 internal friction and wall friction of a coarse-grained bulk material
Without fine particles 100
Annex E (normative) details of bulk material parameters 101
5
-
DIN 1055-6:2005-03
Annex F (normative) determination of the flow profile, mass flow
And core flow 102
Annex G (normative) seismic actions 103
G.1 general 103
G.2 symbols 103
G.3 conditions for calculation 103
G.4 seismic actions 104
G.4.1 silo bottom and foundations 104
G.4.2 silo walls 104
Annex H (normative) alternative rules for determination of hopper loads 106
H.1 general 106
H.2 terms 106
H.3 symbols 106
H.4 conditions for calculation 106
H.5 loads on hopper walls 107
H.6 determination of connecting forces at the hopper junction 108
H.7 alternative equations for the hopper load correction values Fe for
The load discharge 108
Annex I (normative) action due to dust explosions 109
I.1 general 109
I.2 application 109
I.3 additional standards, guidelines and rules 109
I.4 dusts of explosive nature and their parameters 109
I.5 ignition sources 110
I.6 protective measures 110
I.7 calculation of components 111
I.8 calculation of explosive overpressure 111
I.9 calculation of negative pressure 111
6
-
DIN 1055-6:2005-03
I.10 securing the closing element of the discharge opening 111
I.11 recoil forces due to pressure release 111
Diagrams
Diagram 1 illustration of silo bins with nomenclature of geometric
Parameters and loads 9
Diagram 2 basic flow profile 26
Diagram 3 flow profile with pipe flow 27
Diagram 4 flow profile with mixed bulk material flows 28
Diagram 5 effects of slimness (height to diameter ratio) on the mixed bulk
material flows and the pipe flows 28
Diagram 6 customized arrangements for fill and discharge 29
Diagram 7 conditions under which pressures due to mass flow arise 32
Diagram 8 symmetric discharge loads around the vertical silo walls 40
Diagram 9 longitudinal and cross-sectional illustrations of the load diagrams of
reference-surface loads 42
Diagram 11 longitudinal and cross-sectional illustrations of the load
diagrams of reference-surface loads during discharge 47
Diagram 12 flow channels and pressure distribution during discharge
with large eccentricities 52
Diagram 13 loads in low silos or silos with medium slimness after the
fill (fill loads) 56
Diagram 14 fill pressures during eccentric filled low silos or silos with 59
medium slimness
Diagram 15 fill pressures in a braced-wall silo 62
Diagram 16 boundaries between steep and flat hoppers 66
Diagram 17 distribution of the fill pressures in a steep and flat hopper 67
Diagram 18 bottom loads in low silos and in silos with medium slimness 70
Diagram 19 discharge pressures in a hopper with a steep and a flat inclination 72
Diagram B.1 coefficients of pressure for wind loads in circular cylindrical tanks 80
7
-
DIN 1055-6:2005-03
Diagram C.1 equipment for determination of 85 Diagram C.2 test procedure for determination of the coefficients of wall friction 87
Diagram C.3 test procedure for determination of Ko 88
Diagram C.4 test procedure for determination of the angle of the internal
Friction i and c and the cohesiveness based upon the tension Created by pre-compression 90
Diagram C.5 test procedure for determination of the elasticity module during
loading and unloading 94
Diagram D.1 measurement of the profiling of the wall surface 100
Diagram F.1 demarcation of mass and core flow conditions in conical and
cuneiform hoppers 102
Diagram G.1 possible rearrangements oat the bulk material surface due to
Seismic actions 103
Diagram G.2 seismic actions on the substructure (e.g. braces) 104
Diagram G.3 cross-section through the vertical silo shaft with details of
the additional horizontal loads due to seismic actions 105
Diagram H.1 alternative rules for the hoppers 108 Tables
Table 1 classification of conditions for calculation 23
Table 2 relevant parameters for different load estimates 25
Table 3 categories of wall surfaces 34
Table A.1 composite correction values 77
Table C.1 test parameters 91
Table C.2 typical values for the coefficients of variation for the bulk
Material parameters 98
Table E.1 bulk material parameters 101
8
-
DIN 1055-6:2005-03
Foreword
This standard was compiled in the NABau-AA 00.20.00 Actions on Buildings
(Spiegelausschuss zu CEN/TC/ 250/SC 1).
This standard is part of the new series DIN 1055 Actions on Structures, which consists of
the following parts:
Part 1:
Part 2:
Part 3:
Part 4:
Part 5;
Part 6;
Part 7:
Part 8:
Part 9:
Part 10:
Part 100:
9
-
DIN 1055-6:2005-03
References to standards belonging to the series DIN 1055, contained in this standard,
refer exclusively to the above-mentioned new series DIN 1055.
This standard was developed by the Work Committee NABau 00.20.00 on the basis of
DIN V ENV 1991-4 and conforms largely to the draft manuscript prEN 1991-4.
Any deviations of this standard from the above-mentioned manuscript prEN 1991-4
conform by and large with possible commitments to the national safety standards so that,
in the case of an eventual ratification of EN 1991-4, this standard can be compatible in
the national context.
Revisions Vis--vis DIN 1055-6:1987-05 the following revisions have been made:
a) structural adaptation in line with the EN 1991-4
b) terminology adaptation in line with the EN 1991-4
c) adaptation of the calculation and safety concepts in line with the EN 1991-4
d) incorporation of regulations for actions due to dust-explosions
e) incorporation of regulations for actions due to earthquakes
f) incorporation of regulations for actions due to bulk material properties
Earlier Editions DIN 1055-6: 1964-11, 1987-05
10
-
DIN 1055-6:2005-03
1. Scope
1) This standard contains general principles and information relating to the influences
for the design and calculations of silos for storage of bulk materials and for tanks.
It is to be applied in association with the other parts of the series DIN 1055.
2) This standard also contains stipulations for actions on silos and tanks which
extend beyond the direct action caused by the stored bulk material or fluids (e.g.
effects of temperature differences).
3) While applying the rules for calculations made for silo bins and silo structures the
following geometric limitations should be kept in mind:
--- The cross-sections of the silo bins are limited to the instances shown in diagram 1d.
Smaller deviations are allowed under the condition that the possible effects on the silo
structures due to the pressure changes resulting from these deviations will be taken into
account.
--- The foll. Limits will apply for the geometric measurements:
10 2.0, or one which fulfills the additional
conditions given in 5.3
3.1.37 Slimness Ratio of the height to diameter hc / dc of the vertical portion of the silo
3.1.38 Low silo A silo with a height-diameter ratio of 0.4 < hc / dc < 1.0 or one in which the additional
conditions as per 5.3 are fulfilled.
NOTE In case of a height-diameter ratio of hc / dc < 0.4, and if the silo contains a hopper, the silo will fall into the category of a low silo. Otherwise in case of a flat silo bottom it falls into the braced-wall
silo category.
24
-
DIN 1055-6:2005-03
3.1.39 Steep hopper A hopper in which the full wall friction is mobilized after the filling
3.1.40 Stress in the bulk material Force per unit area within the stored bulk material
3.1.41 Tank A structure for storage of fluids
3.1.42 A thick-walled silo A silo with a diameter-to-wall thickness ratio which is less than dc /t = 200
3.1.43 A thin-walled silo A silo with a diameter-to-wall thickness ratio which is greater than dc /t = 200
3.1.44 Wall friction Force per unit area along the silo wall (vertical or inclined) on account of friction between
the bulk material and the silo wall.
3.1.45 Hopper junction The section between the hopper and the vertical silo wall, i.e. the transition from the
vertical part of the silo into the hopper
25
-
DIN 1055-6:2005-03
3.1.46 Vertical Silo shaft The part of the silo which comprises of the vertical walls
3.1.47 Wedge-shaped hopper A hopper in which the surfaces converge at a slit for ensuring an even flow of the bulk
material; the walls of each of the other two hoppers run vertically
3.2 Symbols 3.2.1 General A list of basic symbols (letter symbols) is given in DIN 1055-100. The additional letter
symbols for this part of the standard are given below. The symbols used are based on
the conventions of ISO 3898:1997.
3.2.2 Latin letters, capital
A cross-section of the vertical shaft
Ac cross-section of the flow channel in case of eccentric discharge (large
eccentricities)
B depth parameter in case of eccentrically filled low silos
C load augmentation factor
Co discharge factor (load augmentation factor during discharge) for the bulk material
Cop bulk material parameter for the reference surface load (load augmentation factor)
26
-
DIN 1055-6:2005-03
Cb load augmentation factor for the bottom loads
Ch load augmentation factor for the horizontal discharge loads
Cpe load augmentation factor for the reference surface loads during discharge
Cpf load augmentation factor for the reference surface loads in case of fill loads
CS correction value for slimness in a silo with medium slimness
CT load augmentation factor for making allowance for temperature differences or
changes
Cw correction value for discharge for the wall friction loads (load augmentation factor)
E ratio of eccentricity (during fill and discharge) to silo radius
Es effective elasticity modulus of the stored bulk material at the relevant stress level
Ew elasticity modulus of the silo wall
F relationship between the vertical loads on the silo wall and the mean vertical load
in the bulk material at this point
Fe load ratio in the hopper during the discharge (relationship between loads
perpendicular to the silo wall and mean vertical loads in the bulk material)
Ff load ratio in the hopper after the filling (relationship between loads perpendicular
to the silo wall and mean vertical loads in the bulk material)
27
-
DIN 1055-6:2005-03
Fpe integral of the horizontal reference surface load for thin walled circular silos in the
case of discharge loads
Fpf integral of the horizontal reference surface load for thin walled circular silos in the
case of filling loads
G ratio of the radius of the flow channel to the radius of the internal cross-section of a
circular silo
K characteristic value of the horizontal load ratio
Km mean value of the horizontal load ratio
Ko value of K when horizontal elongation as well as principal stresses that run or are
aligned horizontally and vertically are ruled out
Pwe characteristic value of the sum total of the wall friction loads for each running
meter in the circumferential direction of the vertical silo wall in the case of
discharge loads
Pwf characteristic value of the sum total of the wall friction loads for each running
meter in the circumferential direction of the vertical silo wall in the case of fill loads
PzSk characteristic value of the wall loads for each running meter in the circumferential
direction of the vertical silo wall for low silos and large filling eccentricities
S geometry factors for the hopper loads (= 2 in the case of cone shaped hoppers, =1
in the case of wedge shaped hoppers)
U inner circumference of the cross-section of the vertical silo shaft
28
-
DIN 1055-6:2005-03
Usc (inner) circumferential length of the flow channel in the contact zone up till the non
flow zone of the bulk material during discharge with large eccentricities
Uwc (inner) circumferential length of the flow channel in the contact area with the silo
wall during discharge with large eccentricities
Y depth variation function: function for the description of the increase in load with
increasing depth in the silo
YJ depth variation function of the theory acc. to Janssen
YR depth variation function for small silos
3.2.3 Latin letters, small a side length of a silo with a rectangular or a hexagonal cross-section (see figure 1d)
ax divergence-coefficient (-factor) or conversion factor for calculating the upper and
lower characteristic bulk material parameters from the mean values
aK divergence-coefficient or conversion factor for the horizontal load ratio
a divergence-coefficient or conversion factor for the bulk material specific gravity
a divergence-coefficient or conversion factor for the angle of the internal friction
a divergence-coefficient (-factor) or conversion factor for the coefficients of wall
friction
29
-
DIN 1055-6:2005-03
b width of a rectangular silo (see figure 1d)
b empirical coefficient for the hopper loads
c cohesion of the bulk material
dc characteristic dimensions for the inner cross-section of the silo (see diagram 1d)
e the larger value of the eccentricities ef and eo
ec eccentricities of the central axis of the flow channel during discharge with large
eccentricities (see figure 11)
ef largest eccentricity of the bulk cone at the bulk material surface during filling (see
figure 1b)
ef,cr largest fill eccentricity for which the simplified rules for the allowance for marginal
eccentricities can be used (ef,cr = 0.25dc )
eo eccentricities of the centre point of the outlet opening (see figure 1b)
eo,cr largest eccentricity of the outlet opening for which the simplified rules for the
allowance for eccentricities can be used (eo,cr = 0.25dc )
et eccentricities of the peak of the fill-up cone at the bulk material surface when the
silo is filled up (see figure 1b)
et,,cr largest eccentricity of the fill-up cone at the bulk material surface for which the
simplified rules for the allowance for eccentricities can be used (et,,cr = 0.25dc )
30
-
DIN 1055-6:2005-03
hb overall height of a silo with hopper, measured from the envisaged hopper peak, up
to the equivalent bulk material surface (see figure 1a)
hc height of the vertical silo shaft, measured from the hopper junction up to the
equivalent bulk material surface (see figure 1a)
hh height of the hopper measured from the envisaged hopper top up to the hopper
junction
ho distance between the equivalent bulk material surface and the lowest point at the
base of the bulk material cone (at the lowermost point of the silo wall which is not
in contact with the stored bulk material when the latter has been filled to the
specified extent)(see fig 1, 13 and 17)
htp total height of the back-filled cone at the bulk material surface (vertical distance
from the lowest point of the silo wall up to the tip of filled-up cone when the bulk
material, which is filled to the specified extent, is not in contact with the silo
wall)(see figures 1a and 17)
n parameters in the conditional equations of the hopper loads
p load as force per unit area
ph horizontal load from the stored bulk material (see figure 1c)
phae horizontal load in the area where the bulk material is at rest next to the flow
channel, during a discharge with large eccentricities
phce horizontal load in the flow channel during a discharge with large eccentricities
31
-
DIN 1055-6:2005-03
phco asymptomatic horizontal load at a great depth in the flow channel during a
discharge with large eccentricities
phe horizontal load during discharge
phe,u horizontal load during discharge and use of the simplified calculating method
phf horizontal load after the filling
phfb horizontal loads after the filling at the lower end of the vertical shaft
phf,u horizontal loads after the filling using the simplified calculating material
pho asymptomatic horizontal loads at a great depth from the stored bulk material
phse horizontal loads in the bulk material (which is in a state of rest) at a great distance
from the flow channel during a discharge with large eccentricities
phT increase of horizontal loads as a result of temperature differences or changes
pn loads from the stored bulk material, that are perpendicular to the hopper walls (see
figure 1c)
pne loads during discharge that are perpendicular l to the hopper walls
pnf loads after the fill that are perpendicular to the hopper walls
pp reference surface loads
ppe basic value of the reference surface loads during discharge
32
-
DIN 1055-6:2005-03
ppei complementary reference surface loads during discharge
ppe.nc strip shaped reference surface load for silos with non-circular cross-sections
during discharge
ppf basic value of the reference surface loads after the filling
ppfi complementary reference surface loads after the filling
ppe,nc strip shaped reference surface load for silos with non-circular cross-sections after
the filling
ppes reference surface load at the cylinder ordinate for thin walled circular silos during
discharge
ppfs reference surface load at the cylinder ordinate for thin walled circular silos after
the filling
pt friction load in the hopper (see figure 1c)
pte friction load in the hopper during discharge
ptf friction load in the hopper after the fill
pv vertical load in the bulk material (see figure 1c)
pvb vertical load at the bottom of a low silo
pvf vertical load in the bulk material after the filling
33
-
DIN 1055-6:2005-03
pvft vertical load at the hopper junction after the filling (foot of the vertical silo shaft)
pvho vertical load at the foot of the filled cone at the bulk material surface according to
equation (86) and with the bulk material depth being z = ho
pvsq vertical load on the horizontal bottom of a low silo or a silo of medium slimness
pvtp geostatic vertical load at the foot of the filled cone at the bulk material surface
pw wall friction load along the vertical wall (shear force per unit area due to friction)
(see figure 1c)
pwae wall friction loads in the bulk material which is in a state of rest right next to the
flow channel during the discharge with large eccentricities (at the transition from
stationary to flowing bulk material)
pwce wall friction loads in the flow channel during discharge with large eccentricities
pwe wall friction loads during discharge
pwe,u wall friction loads during discharge using the simplified calculation method
pwf wall friction loads after the filling
pwf,u wall friction loads after the filling using the simplified calculation method
pwse wall friction loads in the bulk material which is at rest at a large distance from the
flow channel during discharge with large eccentricities
r equivalent silo radius (r = 0.5dc)
34
-
DIN 1055-6:2005-03
rc radius of the eccentric flow channel during discharge with large eccentricities
s dimensions of the area subject to the reference surface load (s = dc /16 =
0.2dc)
t thickness of the silo wall
x vertical coordinate in the hopper with origin in the hopper peak (see figure 16)
z depth beneath the equivalent bulk material surface in the filled state (see figure
1a)
zo characteristic depth according to the theory of Janssen
zoc characteristic depth according to the theory of Janssen for the flow channel during
discharge with large eccentricities
zp depth of the mid-point of the reference surface load beneath the equivalent bulk
material surface in a thin-walled silo
zs depth beneath the highest point of contact between the bulk material and the silo
wall (see figures 13 and 14)
zV unit of measurement of the depth for determining the vertical loads in low silos
3.2.4 Greek letters, capital
Horizontal displacement of the upper part of a shear bin
Operator for incremental sizes (see symbols given below)
35
-
DIN 1055-6:2005-03
T Temperature differences between the stored bulk material and the silo walls
v Incremental vertical displacements measured during the material examination
Incremental stress placed upon a specimen during material examination
3.2.5 Greek letters, small
Mean angle of inclination of the hopper walls with reference to the horizontal
w Coefficient of thermal elongation of the silo wall
Angle of inclination of the hopper wall with ref. to the vertical (see figures 1a and
1b) or the angle of the steepest hopper walls in a quadratic or rectangular hopper
Characteristic value for the specific gravity of the stored fluid or the stored bulk
material
l Specific gravity of the bulk material in fluidized state
u Upper characteristic values of the specific gravity of the stored fluid or the stored
bulk material
Standard deviation of a parameter
Cylindrical coordinate: angle in direction of the circumference
c Angle at circumference of the flow channel during discharge with large
eccentricities (see figure 11) with ref to the central axis of the silo shaft
36
-
DIN 1055-6:2005-03
Wall contact angle of the eccentric flow channel with reference to the central axis
of the flow channel
Characteristic value of the wall friction angle at the vertical silo wall
heff Effective or mobilized wall friction coefficient in a flat hopper
h Wall friction coefficient in the hopper
m Mean value of the wall friction coefficients between bulk material and silo wall
Poissons number for the bulk material
c Characteristic value of the angle of internal friction of a precompressed bulk
material in case of relief (i.e. inclusive of the portion from cohesion)
i Characteristic value of the angle of internal friction of a bulk material in case of
equivalent load (i.e. without the portion from cohesion)
im Mean value of the angle of internal friction
r Angle of slope of a bulk material (conical bulk heap) (see figure 1a)
w Wall friction angle (arc tan ) between bulk material and hopper wall
wh Wall friction angle in the hopper (arc tan h) between bulk material and hopper wall
r Reference stress for the tests for determination of the bulk material parameters
37
-
DIN 1055-6:2005-03
4 DESCRIPTION AND CLASSIFICATION OF SILOS 4.1 Description of Actions in Silos
(1) The actions on silos are to be estimated with regard to the silo structure, the
properties of the stored bulk material and the flow profiles that arise during
emptying of the silo.
(2) Ambiguities related to the flow profiles, the influence of the fill and discharge
eccentricities on the fill and discharge processes, the influence of the silo
shape and size on the type of the flow profile and those that are related to the
time-dependant discharge and fill pressures are all to be taken into
consideration
NOTE 1 The magnitude and the distribution of the rated loads depend upon the silo structure, the
material parameters of the bulk materials and the flow profiles which build up during emptying. The
inherent differences in the properties of the different bulk materials that are stored and the
simplifications in the load models lead to variations between the silo loads that actually appear and the
design loads (calculated loads) according to sections 6 and 7. Thus, to quote an example, the
distribution of discharge pressures along the silo wall changes with time. An exact prediction of the
prevailing mean pressure, its divergence and its temporal variability is not possible, given the present
level of knowledge.
(3) Allowance should be made for loads on the vertical walls of the silo when it is
filled and while it is emptying, with fill- and discharge- eccentricities being
marginal; this is to be done using a symmetric load component and an
unsymmetric reference surface load. In case of large eccentricities the loads
are to be described using a pressure distribution curve.
38
-
DIN 1055-6:2005-03
(4) Should the chosen form of the silo structure show a sensitive reaction to
changes of the estimated load-guidelines, allowance has to be made for this
through appropriate investigations
(5) The symmetric loads on the silo walls are to be estimated as follows: a) by
means of horizontal load components ph upon the inner surface of the vertical
silo wall; b) by means of loads pn that act perpendicular to inclined walls; c) by
means of frictional loads pw and pt that act in the tangential direction of the
wall; and d) by means of vertical load components pv in the stored bulk material
(see figure 1c)
(6) The unsymmetric loads on the vertical silo walls in case of marginal
eccentricities during fill and discharge have to be taken into account by using a
reference surface load. These reference surface loads consist of horizontal
pressures ph that act upon the inner surface of the silo wall locally.
(7) The unsymmetric loads on the vertical silo walls in case of large eccentricities
during fill and discharge are to be additionally registered using a unsymmetric
distribution of horizontal pressures ph and friction loads pw
(8) Unplanned and unaccounted load influences are to be registered using the
load augmentation factor C.
(9) The load augmentation factors C for silo cells in categories 2 and 3 (see 4.5)
register unaccounted additional load influences alone, which arise due to the
bulk material flow during emptying of the silo.
(10) The load augmentation factors C for silo bins in category 1 (see 4.5) register
additional influences during emptying that are caused by the bulk material
movement as well as the influences due to the deviation of the bulk material
parameters.
39
-
DIN 1055-6:2005-03
NOTE 2 The load augmentation factors C are intended to cover the ambiguities related to the flow
profile, the influences of eccentricities during filling and emptying, the influence of the shape of the silo
on the manner of the flow profile and proximity influences which arise when allowance is not made for
the presence of fill and discharge pressures that are time dependant. For category 1 silos (see 4.5) the
load augmentation factor also takes into account the deviation of the material properties of the bulk
material. In silos of categories 2 and 3, allowance for the deviation of the material parameters
influenced by the loads is not made by a load augmentation factor C but by the formulation of the
appropriate characteristic calculation values for the bulk material parameters , , K and i.
(11) In silos of category 1 (see 4.5) the allowance for unsymmetric loads is made by
means of an increase of the symmetric loads by applying a load augmentation
factor for the discharge loads C.
(12) In silos of categories 2 and 3 (see 4.5) allowance for the unsymmetric
reference surface loads can be made alternatively by a substitute
augmentation of the symmetric loads.
4.2 Description of Action on Tanks
(1) Allowance for loads on tanks as a consequence of filling them up is made
by hydrostatic load formulations
4.3 Classification of actions on silo bins
(1) Loads due to bulk materials stored in the silo bins are to be classified as
variable actions in accordance with DIN 1055-100.
(2) Symmetric loads on silos are to be classified as variable stationary actions in
accordance with DIN 1055-100.
40
-
DIN 1055-6:2005-03
(3) Reference surface loads for making allowances for the filling and discharge
processes in silo bins are to be classified as variable free actions in
accordance with DIN 1055-100.
(4) Eccentric loads for making allowances for the eccentric filling and discharge
processes in silo bins are to be classified as variable stationary actions.
(5) Loads arising from air or gas pressures in connection with pneumatic conveyor
systems are to be regarded as variable stationary actions.
(6) Loads due to dust explosions are to be classified as extraordinary actions as
defined by DIN 1055-100.
4.4 CLASSIFICATION OF THE INFLUENCES ON TANKS
Loads on tanks that arise due to the filling up of the tanks can be classified as variable
stationary influences acc. to DIN 1055-100.
4.5 STANDARDISED CATEGORIES
(1) Based upon the design of the silo structure and its susceptibility to different types of
malfunctions, various accuracy standards are used in the process of determining the
influences on silo structures.
(2) The silo influences should be determined in accordance with one of the following
standardized categories specified in this standard (see Table 1).
41
-
DIN 1055-6:2005-03
TABLE 1 CLASSIFICATION OF THE DIMENSIONING CONDITIONS
STANDARDISED CATEGORIES
DESCRIPTION
standardized
category 3
Silos with a capacity of more than 10 000 tonnes
Silos with a capacity of more than 10 000 tonnes, in which one of the
foll. calculating conditions is present
a) eccentric discharge with 25.0>c
od
e (see fig 1b)
b) low silos with an eccentric filling of more than 25.0>t
od
e
standardized
category 2
all silos which are covered by this load standard and do not fall in the
other two categories
standardized
category 1 silos with a capacity of less than 100 tonnes
NOTE The differences amongst the categories listed in Table 1 have been determined
taking into account the shortfalls of an exact estimation of the influences. The rules for small silos
are simple and conservative on the safer side, as they have a robustness of their own and high
costs of an estimation of bulk material parameters for example, are not justified.
(3) A higher category for a silo than that which is required as per Table 1 can always be
chosen. For any part of the procedures (computation of loads) described in this standard,
a higher category than that in Table 1 can be taken as a basis, if required.
(4) In case several silos are connected to one another, the suitable category for each
bin should be individually determined, and not for the set of silos as a whole.
42
-
DIN 1055-6:2005-03
5. CALCULATING CONDITIONS 5.1 GENERAL (1) The influences on silos and tanks, for each of the relevant calculating conditions,
are to be determined in compliance with the general specifications contained in DIN
1055-100.
(2) It is important that the relevant calculating conditions be observed and the critical
load types are determined.
(3) The combination rules depend on each of the verifications and are to be chosen in
accordance with DIN 1055-100.
NOTE The relevant combination rules are given in Annex A.
(4) Influences on account of the adjacent building structures are to be taken into
account.
(5) Influences of transporting equipment and pouring equipment are to be taken into
account. Special care is requested in case of permanently installed transporting
equipment. They can transmit loads to the silo structure across the stored bulk materials.
(6) Depending on the circumstances, the following extraordinary influences and
situations are to be taken into account:
- Influences caused by explosions
- Influences caused by vehicular impact
- Influences caused by earthquakes
- Influences caused by fire-load
43
-
DIN 1055-6:2005-03
5.2 CALCULATING CONDITIONS CAUSED BY BULK MATERIAL STORED IN SILOS (1) Loads on silos caused by stored bulk materials are to be ascertained for the
maximum possible state of fullness.
(2) The loads estimates for filling and for discharge can be used as evidence for
supporting safety as well as performance capability.
(3) The dimensioning for filling and for discharge of bulk materials has to comply with
the principal load-types which can lead to differing boundary states for the structure:
- Max loads perpendicular to the vertical silo wall (horizontal loads)
- Max vertical wall friction loads on the vertical silo wall
- Max vertical loads on the silo bottom
- Max loads on the silo hoppers
(4) For determination of loads, the upper characteristic values of the bulk material
specific gravity are to be used always.
(5) The determination of the loads of a load type should always be made for a specific
combination of matching parameters , K and i , so that every boundary state is assigned a specific defined condition of the bulk material.
(6) For each of these load types its extreme value is attained when each of the bulk
material characteristic values , K and i acquires differing extreme values within the variance range of their characteristic bulk material parameters. In order to ensure
adequate safety for all boundary states during dimensioning, differing combinations of the
extreme values of these parameters have to be examined. Table 2 gives the extreme
values of the bulk material parameters which are to be used for each load types that are
to be examined.
44
-
DIN 1055-6:2005-03
TABLE 2 - VITAL PARAMETERS FOR THE DIFFERENT LOAD CALCULATIONS
CHARACTERISITC VALUE TO BE CALCULATED
TYPE OF LOAD EXAMINED COEFFICIENT OF
WALL FRICTION
HORIZONTAL LOAD
RATIO
K
ANGLE OF INTERNAL
FRICTION
i SECTION OF VERTICAL WALL Max. horizontal load ratio
perpendicular to the vertical wall Lower limit value Upper limit value Lower limit value
Max. wall friction loads on the
vertical walls Upper limit value Upper limit value Lower limit value
Max. vertical loads on the hopper
or the silo bottom Lower limit value Lower limit value Upper limit value
Type of load examined Coefficient of wall friction
Load ratio in the hopper
F Angle of internal friction i
HOPPER WALLS Maximum hopper loads in the
filled state
Lower limit value for the
hopper Lower limit value Lower limit value
Maximum hopper loads during
discharge Lower limit value for the
hopper upper limit value upper limit value
NOTE 1 It is to be noted that the wall friction angle is always smaller or same as the angle of internal friction of the
stored bulk material ( )iwhei .. . Otherwise, when transverse stresses recorded at the wall contact surface are larger than those due to the internal friction of the bulk material itself, a slide surface develops within the bulk material. This means
that in all cases the coefficient of wall friction should not be taken as larger than tan i ( )iw tantan =
NOTE 2 The loads that are perpendicular to the hopper walls are as a rule largest when the wall friction in the
hopper is small, because thereby a smaller portion of the loads in the hopper are take away are removed through friction. It
is to be observed which maximum parameters become decisive for the individual dimensioning exercises (i.e. it is the
malfunctioning that is being examined, which determines whether the wall friction loads or loads that are perpendicular to
the hopper wall are to be calculated as maximum)
np
45
-
DIN 1055-6:2005-03
(7) The above table notwithstanding, silos of category 1 can be dimensioned using the
mean values of the bulk material parameters, namely the mean value of the coefficient of
wall friction m , the mean value of the horizontal load ratio and the mean value of the angle of internal friction
mK
im .
(8) The fundamental equations for calculating the silo loads are given in sections 7
and 8. These are to be taken as the basis for the calculation of the following
characteristic loads:
- Filling loads on vertical wall sections (see section 7)
- Discharge loads on vertical wall sections (see section 7)
- fill and discharge loads on horizontal bottoms (see section 8)
- Fill loads on hoppers (see section 8)
- Discharge loads on hoppers (see section 8)
5.3 CALCULATING CONDITIONS CAUSED BY DIFFERING GEOMETRIC DESIGNS OF THE SILO GEOMETRY (1) Differences in slimness of silos (ratio of height to diameter), hopper geometries
and arrangements of vents lead to differences in calculating conditions and these
have to be observed.
(2) In a silo that has been filled-up, the trajectory of the filling stream of the filled up
bulk material may at times cause the build-up of an eccentric back-fill cone at the
bulk material surface (see fig 1b) and when this happens different storage
densities can arise in different parts of the silo which lead to un-symmetric loads.
While calculating the size of these loads, the largest possible eccentricity of the
filling stream is to be taken as a basis (see 7.2.1.2 and 7.3.1.2)
46
-
DIN 1055-6:2005-03
(3) While dimensioning, the effects of the flow profiles are to be observed which can
be divided into the following Categories (see fig. 2):
-- Mass flow
-- funnel flow
-- mixed flow
1
2
3
4 4
3
5
4 4
2 a) MASS FLOW b) CORE FLOW C)CORE FLOW
(FUNNEL FLOW) (MIXED FLOW) Legend 1 Entire bulk material in motion 4 Bulk material at rest
2 flow 5 Effective passages
3 Limits of flow channel 6 Effective hopper
Figure 2 BASIC FLOW PROFILES
47
-
DIN 1055-6:2005-03
(4) If it can be additionally ensured during funnel flow that the flow channel is always
located within the bulk material without coming into contact with the silo wall (see figures
3a and 3b), the emptying pressures can be ignored. Low silos with concentric discharge
aided by gravity and silos with a mechanical discharge system located at the bulk
material surface which ensures a build-up of funnel flow (see fig. 5a, 5b and 6a) fulfill
these conditions (see fig. 7.1 (9) and 7.3.2.1(2) and (4)).
NOTE A suitably designed central tube with lateral vents (anti dynamic tube) can
also ensure that this condition - i.e. building up an internal funnel flow - is fulfilled.
(5) In case of symmetric mass flow or a mixed flow (see fig. 2), the un-symmetric
loads that usually occur are to be taken into account during the dimensioning (see
7.2.2.2 and 7.3.2.2).
(6) In case of flow profiles with core flow (see fig 2) and partial contact of the moving
bulk material mass with the silo wall, other un-symmetric load components which
may arise specifically in this case are to be taken into account during
dimensioning (see fig 3c and 3d as well as fig 4b and 4c) (see 7.2.4).
(7) For silos with several vents and presuming a state of maximum fullness, one has
to take into account that during operation either all the vents may be opened
simultaneously or a single vent alone may be open.
(8) For silos with several vents, provisions of the combination of active vents for the
operation are to be regarded as normal calculating conditions. Other openings
which are not part of the planned operation are to be regarded as extraordinary
calculating conditions.
48
-
DIN 1055-6:2005-03
(9) In case of an eccentrically filled very slim silo
> 4..c
cd
hei , the effects of mixed
flow in different areas could lead to either differing packing densities or cohesion of
the bulk material. In such cases the asymmetric alignment of the bulk material
particles can set off a un- symmetric core flow (see fig. 5d). This creates zones in
the silo where the bulk material flows along the silo wall and thereby gives rise to
un-symmetric loads. For such cases special load computations are to be used
(see 7.2.4.1 (2)).
1
2
3
1
2
3
2
3 4
1
4
1
2
3
INTERNAL CONVERGENTINTERNAL PARALLEL ECCENTRIC CONVERGENT ECCENTRIC PARALLEL Funnel flow funnel flow funnel flow funnel flow Legend 1 flow
2 flow channel limits
3 flowing funnel
4 bulk material at rest
Figure 3 FLOW PROFILES WITH FUNNEL FLOW
49
-
DIN 1055-6:2005-03
1 3
6
31
6
2
1
3
4
5 5
(A) (B) (C) a) Concentric mixed flow b) Fully eccentric mixed flow c) Partially eccentric mixed flow Legend
1 At rest
2 Effective hopper
3 Limits of flow channel
4 Effective passage
5 Flow zone
6 Effective passage varies in the silos circumferential direction
Figure 4 FLOW PROFILE WITH MIXED FLOW OF BULK MATERIAL
50
-
DIN 1055-6:2005-03
]
2
1
2
1
5
4
5
3
1
4 5
1
2
a) Braced wall silo b) Low silo c) Slim silo d) Very slim silo Legend 1 Bulk material at rest
2 Flow channel limits
3 Effective hopper
4 Effective passage
5 Flow
Figure 5 EFFECTS OF THE SLIMNESS (RATIO OF HEIGHT TO DIAMETER) ON THE MIXED FLOW OF THE BULK MATERIAL AND THE FUNNEL FLOW
51
-
DIN 1055-6:2005-03
(10) For silos with pneumatically conveyed powdery bulk materials two calculating
conditions, both at maximum fullness, are to be considered:
- The bulk material filled in can develop a cone, as is the case with other bulk
materials.
- It is to be taken into account that the bulk material surface, independent of the
gradient of slope and the filling eccentricities, could possibly also be of even shape
(see fig 6c). In this case the eccentricities and can be fixed at zero. fe te
(11) In case of silos for storage of powdery bulk material where air-injection is used as
a discharge aid in the bottom area, (see fig 6b), the entire bulk material zone near
the bottom can become fluidized, which can generate an effective mass flow even
in low silos. Such silos are to be computed in accordance with the procedure for
slim silos, regardless of their actual slimnessc
cd
h .
(12) In case of silos for storage of powdery bulk material where air-injection is used as
a discharge aid in the bottom area, (see fig 6b), just a part of the bulk material
zone near the bottom can become fluidized. This can generate an eccentric mass
flow (see fig 4b), which is to be taken into account while dimensioning. The
eccentricity of the resultant flow channel and the resultant value of the eccentricity
that is to be computed are to be derived keeping in mind the fluidized zone, in
addition to the position of the vent.
0e
(13) The vertical silo walls with a discharge hopper which causes an expanded flow
(see fig 6d), can form the basis of the conditions for a mixed bulk material flow.
This can lead to un-symmetric discharge loads. In this type of silo the ratio
c
bd
h can be fixed for slimness instead of c
cd
h (see fig 1a).
52
-
DIN 1055-6:2005-03
(14) A silo with a slimness of c
cd
h smaller than 0.4 and with a funnel hopper is to be
graded as a low silo. In case of a horizontal silo bottom this silo is to be graded as
a braced wall silo.
a) Mechanically aided discharge e.g. with a rotating space arm b) Air injection and air vents generate mass flow c) Pneumatic filling of powdery bulk material generally results in a level bulk
material surface d) Expanded flow hoppers lead to mass flow at least in the lower hopper Figure 6 - SPECIAL FILLING AND SICHARGE ARRANGEMENTS
53
-
DIN 1055-6:2005-03
5.4 CALCULATING CONDITIONS CAUSED BY SPECIFIC STRUCTURAL SHAPES OF SILOS
(1) In case of dimensioning of silos fro usability, the size of fissures is to be limited to
suitable dimensions. The inspection of fissure size has to comply with the fissure
size limitation specified in DIN 1045-1 subject to the exposition categories based
on the ambient conditions of the silo.
(2) For metal silos which mainly consist of nuts and bolts, the specifications for un-
symmetric load values (reference surface loads) are to be complied with.
(3) For metal silos with rectangular cross-sections that contain beam ties within the
silo shaft for reducing the walls bending moment, the specifications in 7.7 are to
be followed.
(4) The effects of fatigue in silos and tanks are to be taken into account if they are
exposed to a load cycle more than once a day on an average. A load cycle is
equivalent to a complete filling and emptying cycle of a silo or, in the case of a air-
injection silo, a complete process conclusion (rotation) of the sectors subjected to
air-injection. Fatigue effects are also to be taken into consideration in silos which
are exposed to the influence of vibrating machines/equipment components.
(5) Prefabricated silos are to be dimensioned for the influences related to
manufacture, transport and assembly.
(6) In case of slip openings or observation holes in the silo or hopper walls, the loads
on the stopper covers are to be taken into account using double the value of the
maximum load-values upon the adjacent wall sections. These loads are to be
computed only for the dimensioning of the stopper cover and its support or
attachment structures.
54
-
DIN 1055-6:2005-03
(7) If the silo roof has to bear loads imposed by dust filtering equipment, cyclones or
mechanical transporting equipment, then these loads are to be treated as live
loads.
(8) If pneumatic transport systems are used for filling and emptying of silos, then
loads resulting from differences in air-pressure are to be taken into account.
NOTE These loads normally amount to
-
DIN 1055-6:2005-03
5.6 PRINCIPLES OF DIMENSIONING FOR EXPLOSIONS
(1) As the liquids or bulk material stored in tanks or silos respectively may have a
tendency to explode, the potential damage could be limited or avoided by means
of the following measures:
-- Arrangement of adequate pressure relief areas
-- Arrangement of adequate explosion suppression systems
-- designing/dimensioning the structure for absorbing the explosive pressures
(2) A few bulk materials which are prone to explosions are listed in Annex I.
(3) The instructions given in Annex I for the explosion loads are to be followed.
Further instructions including rules for dimensioning for dust explosions can be
taken from DIN-Fachbericht 140.
(4) The effects of silo structure dust explosions upon the surrounding structures or
structural parts are to be taken into account.
6 BULK MATERIAL PARAMETERS 6.1 General
(1) For the estimation of silo loads the following influences have to be taken into
account:
the divergences from the bulk material parameters the fluctuations of the wall friction at the silo wall the silo geometry the filling and emptying processes
56
-
DIN 1055-6:2005-03
(2) Influences which have a favourable impact upon the bulk material stiffness may
not be taken into account while determining the loads and examining the
stability of the wall. A positive impact of a wall deformation upon the pressures
which develop in the bulk material may not be estimated, except if a
reasonable and verified method of calculation can be proved.
(3) If required, the manner of the flow profile (mass or core flow) is to be
determined from figure 7. Figure 7 may be used on the grounds of simplifying
hypotheses that have been taken as a basis - for example, the influence of
internal friction is ignored but may not be used for technical layout of silos.
NOTE The layout of the silo geometry for a mass flow is beyond the scope of this standard. The methods and procedures specific to bulk material technology have to be used for this purpose.
(a) conical hopper
0
0.2
0.4
0.6
0.8
1
1.2
0 20 24 40 60
Series1
1
2
Co-
effic
ient
of w
all f
rictio
n in
the
hopp
er
h
Angle of inclination of hopper
57
-
DIN 1055-6:2005-03
(b) cuneiform hopper
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 8
0
Series1
Co-
effic
ient
of w
all f
rictio
n in
the
hopp
er h
1
2
Angle of inclination of hopper
Legend 1 area with core flow
2 areas with the possibility of mass flow
Figure 7 CONDITIONS UNDER WHICH PRESSURES CAUSED BY MASS FLOW ARISE
6.2 Bulk Material Parameters 6.2.1 General
(1) The material properties of the bulk material stored in the silos, which are to be
quantified for calculating the loads, are to be derived or obtained either as test results or
as data in any other suitable form.
(2) While using values from test results and other sources of data, the same are to be
evaluated in a suitable manner keeping in mind the type of load in question in each case.
58
-
DIN 1055-6:2005-03
(3) It should be kept in mind that there may be significant differences between the
material parameters measured in tests and the parameters that are determined by the
actual behaviour of the bulk material in the silo.
(4) While evaluating the differences in bulk material parameters mentioned in (3), the
following are some of the factors that must be kept in mind:
a lot of parameters are not constant, and may be dependant upon the stress level and the background of load application
Influences on account of particle shape, sizes and distribution of grain size can have a strong impact on the test and the silo in a variety of ways.
temporal influences
fluctuations of the moisture content
influences of dynamic actions
brittleness or ductility of the tested bulk material
the manner of putting-in the bulk material in the silo and in the testing apparatus
(5) While evaluating the differences in bulk material parameters mentioned in (3) with
ref. to the coefficients of wall friction, the following factors must be kept in mind:
corrosion and chemical reaction of the bulk material particles, dampness and the wall
abrasion and wear which can roughen or smoothen the wall of the silo
59
-
DIN 1055-6:2005-03
polishing of the wall surface
accumulation of fat deposits on the wall
particles which get impressed in the wall surface (usually an influence which leads to the roughening of the wall surface)
(6) While determining the values for the material parameters the following is to be
kept in mind:
the facts regarding the application of the relevant tests should be well-publicised and common knowledge
a comparison of the values of the individual parameters which have been measured in the tests with the corresponding published parameters, taking
into account the experimental values
the deviation of the parameters relevant to the calculations
the results obtained from the large scale measurements on silos of similar styles
correlation of results from different types of tests
perceptible changes in the material parameters during the period when the silo is in use
(7) The choice of the characteristic material parameters has to be made on the basis
of values the have been determined through laboratory tests, with due regard for
know-how acquired through experience.
60
-
DIN 1055-6:2005-03
(8) The characteristic value of a material is to be chosen after a careful evaluation of
the value which has influenced the occurrence of the load.
CATEGORY DESCRIPTION OF WALL-
SURFACE TYPES OF MATERIAL
D1 Polished
Cold-rolled stainless steel
Scarred stainless steel
Polished stainless steel
Galvanized carbon steel
Aluminium
Extruded high-density polyethylene
D2 Smooth
Carbon steel with slight surface corrosion
Coated carbon steel
Cast high-density polyethylene
Smooth ceramic plates
Concrete surface manufactured with steel shell
D3 Rough
Rough shell concrete
Scarred carbon steel
Steel silos with bolts on the inside surface of the
wall
Roughly polished ceramic plates
D4 Corrugated
Horizontal corrugated wall
Contoured sheet metal with horizontal notches
Non-standardised walls with large deviations
The effect of wrinkling in these surfaces has to be very carefully examined by means of the
particles embedded in the wall surface.
NOTE The classification and description given in Table 3 refers to the friction
rather than the roughness. The main reason for this is that there is only a small
correlation between the degree of roughness and the measured amount of wall friction
caused by the bulk material that slides along the wall surface.
61
-
DIN 1055-6:2005-03
6.2.2 Determination of the Bulk Material Parameter (1) The material parameters to be used for the design calculation may have deviations
due to the changes in the structure, the production procedure, the grain size
distribution, moisture content, age and electrical charging during handling; these
need to be taken into account.
(2) The bulk material parameters are to be determined either according to the
simplified procedure laid down in 6.2.3 or by means of test measurements in
accordance with 6.3.
(3) Bulk materials parameters which are not contained in Table E.1 are to be obtained
by means of test measurements in accordance with 6.3.
(4) The calculated correction values for the coefficient of wall friction of the bulk
materials should take into account the roughness of the wall surface along which
they glide. In Table 3 the different classes of wall surfaces are defined for use in
this standard.
(5) For silos with wall surfaces belonging to the class (category) D4 according to
Table 3, the effective wall friction coefficients should be determined according to
the procedure described in D.2.
(6) The bulk material correction value Cop for the reference surface loads is to be
taken from Table E.1 or calculated according to the equation (8).
6.2.3 Simplified Procedure
(1) The parameters of commonly known bulk materials are to be taken from the Table
E.1. The values given there for the specific gravity correspond to the upper
62
-
DIN 1055-6:2005-03
characteristic value, while the parameters for the wall friction m, for the horizontal
load ratio Km and for the angle of the internal friction im represent mean values of
these characteristic quantities.
(2) If individual bulk materials cannot be clearly classified under the bulk material
categories listed in Table E.1, then their parameters are to be determined
experimentally in accordance with the procedure described under 6.3
(3) For determining the characteristic parameters of , K and i, the listed values of
m, Km and im are to be multiplied or divided by the so called conversion factor.
The conversion factors ax are given in the table E.1 for the bulk materials listed
therein. For calculating the maximum loads, the following combinations are to be
used:
Upper characteristic value of mk KaK = (1)
Lower characteristic value of k
ma
KK = (2)
Upper characteristic value of ma = (3) Lower characteristic value of
am= (4)
Upper characteristic value of imi a = (5) Lower characteristic value of
aimi = (6)
(4) For determining the effect of action on silos of the requirement category 1, the
mean values m, Km and im may be used instead of the upper and lower characteristic
values.
63
-
DIN 1055-6:2005-03
6.3 Measurement of Bulk Material Parameters in Tests 6.3.1 Experimental Determination (Measuring System)
(1) The experimental determination of the parameters is to be executed with
representative bulk material specimens. For every bulk material property a mean value of
the relevant parameter is to be determined keeping in mind the deviation of its relevant
so-called secondary influence parameter such as bulk material structure, filtering curve,
moisture content, temperature, age and the possibility of electrical charging during
operation or manufacture.
(2) The characteristic values are derived from the experimentally determined mean
values with the aid of equations (1) to (6) and the corresponding conversion factors ax.
(3) Each conversion factor ax is to be carefully determined. While determining the
same one should take into account the fact that the bulk material parameters can
undergo a change during the service life of the silo. Likewise, the possible consequences
of the sedimentation phenomena in the silo and the inaccuracies during processing of the
material specimens are to be taken into account.
(4) If the test data is there, the conversion factors ax are to be ascertained acc. to
C.11 in order to determine the standard deviation of the parameters.
(5) The span between the mean value and the characteristic value of the bulk material
parameter is expressed by the conversion factor ax. If a secondary influence parameter is
by itself responsible for more than 75% of the conversion factor ax, it has to be raised by
a factor of 1.10.
NOTE The above-mentioned specifications serve to ensure that the values of xx adequately represent the probability of occurrence for the derived loads.
64
-
DIN 1055-6:2005-03
6.3.2 Specific Gravity of the Bulk Material (1) The specific gravity of the bulk material is to be determined for such a packing
density of the bulk material particles and at such a pressure-level, which corresponds to
the packing density or the pressure level that is present in the zone of maximum vertical
fill-pressure bzw in the silo. The vertical pressure Pvft can be determined from the
equations (11) or (86) for the depth of the bulk material at the lower end of the silo shaft.
(2) For measuring the specific gravity the test procedures acc. to C.6 should be used.
(3) The conversion factor for deriving the characteristic value from the measured
value is to be determined in accordance with the procedure described in C.11. The
conversion factor a may not be less than a = 1.10, except when a smaller value can be
separately established through tests or a suitable estimation (see C.11).
6.3.3 Coefficient of Wall Friction
(1) The experimental determination of the coefficients of wall friction for the estimation of loads is to be determined for such a packing density of the bulk material
particles and at such a pressure-level, which corresponds to the packing density or the
pressure level that is present in the zone of maximum horizontal fill-pressure Phfb in the
silo. The pressure level Phfb can be determined from the equations (9) or (78) for the
depth of the bulk material at the lower end of the zone with vertical walls. (2) For measuring the coefficients of wall friction the test procedures acc. to C.7 should be used.
(3) The mean value m of the coefficients of wall friction and its standard deviation are to be determined and derived through tests. If only one mean value can be ascertained
from the data material, the standard deviation is to be estimated in accordance with the
method described in C.11.
65
-
DIN 1055-6:2005-03
(4) The conversion factor for deriving the characteristic value from the measured
value is to be determined in accordance with the procedure described in C.11. The
conversion factor may not be less than a = 1.10, except when a smaller value can be
separately established through tests or a suitable estimation (see C.11).
6.3.4 Angle of Internal Friction i (1) The angle of internal friction i for the calculation of loads is to be determined as arc tangents from the ratio of the shear force to the normal force at the break under
equivalent load - for such a packing density of the bulk material particles and at such a
pressure-level, which corresponds to the packing density or the pressure level that is
present in the zone of maximum vertical fill-pressure Pvf. The pressure level Pvf can be
determined from the equations (11) or (86) for the depth of the bulk material at the lower
end of the zone with vertical walls.
(2) For measuring the angle of internal friction i the test procedures acc. to C.9 should be used.
(3) The mean value im of the angle of internal friction and its standard deviation are to be determined and derived through tests. If only one mean value can be ascertained
from the data material, the standard deviation is to be estimated in accordance with the
method described in C.11.
(4) The conversion factor for deriving the characteristic value from the measured
value is to be determined in accordance with the procedure described in C.11. The
conversion factor a may not be less than a = 1.10, except when a smaller value can be
separately established through tests or a suitable estimation (see C.11).
66
-
DIN 1055-6:2005-03
6.3.5 Horizontal Load Ratio K
(1) The horizontal load ratio K for the estimation of loads (the ratio of mean horizontal
pressure to mean vertical pressure) is to be determined for such a packing density of the
bulk material particles and at such a pressure-level, which corresponds to the packing
density or the pressure level that is present in the zone of maximum vertical fill-pressure.
The pressure level pvft can be determined from the equations (11) or (86) for the depth of
the bulk material at the lower end of the zone with vertical walls.
(2) For measuring the horizontal load ratio K the test procedures acc. to C.8 should be
used.
(3) The mean value Km of the horizontal load ratio and its standard deviation are to be
determined and derived through tests. If only one mean value can be ascertained from
the data material, the standard deviation is to be estimated in accordance with the
method described in C.11.
(4) An approximate value for Km can be alternatively calculated according to the foll.
Equation (7) from the mean value of the angle of internal friction for first load application
im determined through tests (see 6.3.4)
Km = 1.1 (1- sin im) (7)
NOTE The factor 1.1 in equation (7) is used in order to ensure an appropriate derivative unit of measure for making allowance for the difference between a value of K (= Ko ) that was
measured under virtually absent wall-friction influences and a value of K that was measured in
the presence of wall friction influences (see also 6.2.2 (5)).
67
-
DIN 1055-6:2005-03
(5) The conversion factor for deriving the characteristic value from the measured
value is to be determined in accordance with the procedure described in C.11. The
conversion factor aK may not be less than aK = 1.10, except when a smaller value can be
separately established through tests or a suitable estimation (see C.11).
6.3.6 Cohesion c
(1) The cohesion of bulk material varies with the consolidation stress to which the
specimen is subjected. It is to be determined for such a packing density of the bulk
material particles and at such a pressure-level, which corresponds to the packing density
or the pressure level that is present in the zone of maximum vertical fill-pressure Pvf. The
pressure level Pvf can be determined from the equations (11) or (86) for the bulk material
depth at the lower end of the zone with vertical walls.
(2) For measuring the cohesion c the test procedures acc. to C.9 should be used.
NOTE Alternatively the cohesion can be estimated by means of results of tests in the shear cells of Janike. A method for calculating the cohesion from test results is to be taken from C.9.
6.3.7 Bulk material Correction Value for the Reference Surface Load Cop (1) The bulk material correction value for the reference surface load Cop is to be
estimated on the basis of suitable test data.
NOTE 1 The discharge factors C make allowances for a host of phenomena which arise during the
emptying of silos. The symmetric increase of pressures is relatively independent of the stored bulk material,
yet the unsymmetric components are greatly dependant upon the material. The material-dependency of the
unsymmetric components is represented by the bulk material correction value Cop . This parameter is not
easy to determine with the help of experimental test procedures.
68
-
DIN 1055-6:2005-03
NOTE 2 A suitable experimental test procedure for the parameter Cop has not so far been
developed. This factor is therefore based on evaluations of tests on silos and on experimental values of
silos with conventional filling and discharge systems, which were established within the usual structural
tolerances.
(2) Values for the bulk material correction values for the reference surface load Cop of
commonly known bulk materials are to be taken from Table E.1.
(3) For materials which are not listed in Table E.1, the bulk material correction value
for the reference surface load can be estimated from the divergence factors for the
horizontal load ratio aK and the wall friction correction value a acc. to equation (8):
Cop = 3.5 a = 2.5 aK 6.2
Where
a divergence factor for the coefficients of wall friction ;
aK divergence factor for the horizontal load ratio K of the bulk
Material.
(4) For special silos or special bulk materials (in the individual case) the suitable bulk
material correction value for the reference surface load Cop can be estimated by means of
large scale experimental investigations in silos with designs that are comparable.
7 LOADS ON VERTICAL SILO WALLS 7.1 General (1) For the filling and the emptying types of loads, the characteristic values of the
loads described in this section have to be fixed. For this purpose the loads are
differentiated as follows:
69
-
DIN 1055-6:2005-03
slim silos silos of medium slimness low silos braced walls silos (silos consisting of braced walls) silos for the storage of bulk materials air pockets between the bulk material
particles (for example, due to pneumatic discharge aids and homogenizing
silos)
silo hoppers and silo bottoms
(2) The loads on the vertical silo walls are to be determined in accordance with the
following criteria pertaining to the slimness of the silos:
slim silos, with 2.0 < hc / dc (with exceptions acc. to 5.3) silos with medium slimness, with 1.0 < hc / dc < 2.0 (with exceptions acc. to
5.3)
low silos, with, 0.4 < hc / dc < 1.0 (with exceptions acc. to 5.3) braced wall silos (silos consisting of braced walls) with horizontal bottoms
and hc / dc < 0.4
silos for bulk materials with air pockets between the bulk material particles
(3) A silo with an aerated bottom is to be handled independent of its actual slimness
hc/ dc -- like a slim silo.
(4) The loads on the vertical walls are made up of a stationary load component, the
symmetrical loads and a free load component, the reference surface loads. Both the
components are to be assessed as acting simultaneously.
(5) Special types of loads are to be taken into account for large fill and discharge
eccentricities. These are not to be placed simultaneously with the symmetrical and
reference surface loads; each represents a separate and clearly defined load category.
70
-
DIN 1055-6:2005-03
(6) Detailed guidelines for the calculation of fill and discharge loads are given within
the context of silo slimness in sections 7.2, 7.3 and 7.4.
(7) Rules for the additional types of loads for special types of silos and special design
conditions are given in 7.5 till 7.7:
see 7.5 for silos with air injection equipment for complete or partial fluidization of bulk material
see 7.6 for loads due to hot-filled bulk materials see 7.7 for loads in rectangular silos
(8) For circular silos with large fill and discharge eccentricities, load estimates are
given in 7.2.4. For non-circular silo bins corresponding load estimates should be derived
from these load estimates, if they are found to be suitable for design calculations.
(9) If funnel flow can be ensured within the bulk material without contact points
between the flow zone and the silo walls (see 5.3 (4)), the calculations can be limited to
the estimates of the filling loads, in which case the reference surface loads are to be
taken into account along with these, if required.
7.2 Slim Silos 7.2.1 Fill Loads on Vertical Walls 7.2.1.1 Symmetric Fill Loads
(1) The symmetric fill loads (see figure 8) are to be calculated acc. to the equations
(9) to (14).
71
-
DIN 1055-6:2005-03
(2) After the filling is done and during the storage of the bulk material, the horizontal loads
Phf, the wall friction loads Pwf and the vertical loads Pvf are to be estimated as follows:
(9) ( ) ( )zYPzP jhohf =
( ) ( )zYPzP jhowf = (10)
( ) ( )zYKPzP jhovf = (11)
With
oho KzP = (12)
UA
Kzo
1= (13)
( ) ozzj ezY =1 (14) Where
The characteristic value of the bulk material specific gravity
The characteristic value for the coefficients of wall friction for the bulk material at the vertical silo walls
72
-
DIN 1055-6:2005-03
K The characteristic value of the horizontal load ratio
z The depth of the silo material beneath the equivalent surface of the bulk
material
A The inner cross-sectional area of the silo
U The circumference of the inner cross-sectional area of the silo
(3) For the status after the filling is done, the resultant characteristic value of the wall
friction loads Pwf that have been added-up up till depth z with the force per unit of length
in the direction of the circumference e.g. [kN/M] is calculated using:
(15) ( ) ( )[ ]zYzzPdzzPP johoz wfwf == 0
(4) For determining the characteristic values for the required bulk material parameters
(specific gravity (), correction value for wall friction and horizontal load ratio K), the values given in 6.2 and 6.3 are to be used.
7.2.1.2 Reference Surface Load for Filling Loads: General Requirements
(1) For making an allowance for unplanned unsymmetrical loads due to eccentricities
and imperfections during the filling of the silos, reference surface loads or other suitable
load arrangements are to be placed.
(2) For silos of category 1 the reference surface load can be ignored for the filling
loads.
73
-
DIN 1055-6:2005-03
Legend 1 equivalent bulk material surface
1
vfPwfP
wfP
z
hchfP
z1
hfP Figure 8 SYMMETRIC FILLING LOADS NEAR THE VERTICAL SILO WALLS
3) For silos in which powdery bulk material is stored and which are filled with the help
of air injection equipment, the placing of reference surface loads for the filling loads can,
as a rule, be done away with.
(4) The amount of reference surface load to be placed for the filling loads Ppf is to be
estimated on the basis of the maximum possible eccentricity ef the filled cone that
appears at the surface of the bulk material (see fig. 1b).
(5) The fundamental value of the reference surface load for the filling load Ppf is to be
fixed with:
hfpfpf PCP = (16)
74
-
DIN 1055-6:2005-03
With:
( )
+=
15.1
2 12121.0 cc
dh
oppf eECC (17)
c
f
de
E2= (18)
But pfC > 0 (19)
Where
fe Is the maximum eccentricity of the filled cone which appears at the
Bulk material surface during filling;
hfP Is the local value of the horizontal fill pressure acc. to equation (9) at
the position at which the reference surface load is placed
opC Is the correction value of the bulk material for the reference surface
load (see table E.1).
(6) The height of the zone at which the reference surface load is to be placed (see
figures 9 and 10) amounts to:
cc dds 2.0
16= (20)
(7) The reference surface load consists of only a horizontally acting load component.
There are no frictional forces to be taken into account as a result of these
horizontal load components.
75
-
DIN 1055-6:2005-03
(8) The form of the reference surface load for the filling loads depends upon the
structural design of the silo. The following structural designs of silos can be
distinguished with respect to the reference surface load to be placed:
-- Thick walled silos with circular cross-section see figure7.2.1.3 (e.g.
reinforced concrete silos);
-- thin walled silos with circular cross sections, see figure 7.2.14 (e.g. metal
silos without braces);
-- Silos with non-circular cross-sections, see 7.2.1.5
a) Thin walled circular silo b) other circular silo
S
Ppf1
Ppf
PpfPpf
S S
S
z php
a
hc
Ppfs
Ppf
h
Ppf
Figure 9 - Longitudinal Section and Transverse SectionDiagrams of the Reference Surface Loads b
s
Showing the Load
76
-
DIN 1055-6:2005-03
Ppe,ncPpf,nc
P pe,
nc
P pf,n
c
P pe,
nc
] p
pf,n
c
S
a
h c
S a
h c
Legend
a smaller value of zo and hc/2
b as per choice
Figure 10 LONGITUDNAL SECTION AND TRANSVERSE SECTION SHOWING THE LOAD DIAGRAMS OF THE REFERENCE SURFACE LOADS FOR NON-CIRCULAR SILOS
77
-
DIN 1055-6:2005-03
7.2.1.3 Reference Surface Load for Filling Loads: Thick-Walled Circular Silos
(1) For thick-walled circular silos of the categories 2 and 3, the fundamental value of
The reference surface load for the filling load is to be estimated as it acts outwards pfP
Along the opposite sides of a quadratic reference surface with the side length s (see
equation (20)). The unit of measurement for the side length s should be applied to
the curved surface in a suitable manner.
2) In addition to the reference surface load that acts outwards, a complementary pfP
Reference surface load that is directed inwards is to be placed in the remaining
portion of the silo circumference above the same wall-height (see fig. 9b):
pfiP
pfiP = 7pfP (21)
Where
pfP is the fundamental value of the reference surface load acting outwards
for the filling loads acc. to equation (16)
NOTE The amount and the impact area of the load which is directed inwards are chosen
such that the resultants of both the load components counterbalance each other in the
middle at the position at which these are to be placed.
pfiP
(3) The reference surface load for the filling loads is to be placed at any
position on the silo wall. However it may be placed in accordance with the manner
described in 7.2.1.3(4).
(4) In thick-walled circular silos of category 2, a simplified proof may be furnished.
Half the height of the vertical bin shaft may be regarded as the most unfavourable
Position for placing the reference surface load. The largest percentage increase of the
dimensioning sections which result from the placing of reference surface loads at this
78
-
DIN 1055-6:2005-03
position can be carried over to the other areas of the wall by multiplying over there the
design sectional sizes with the value of the ratio between the horizontal fill pressure at
the observed position and the horizontal fill pressure at the position where the reference
surface load was placed.
7.2.1.4 Reference Surface Load for the Filling loads: Thin-Walled Circular Silos
(1) For thin-walled circular silos (dc/t > 200)