National Farm Building Code, Useful Calculations
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Bulk Densities of Agricultural Materials and Other Useful Equations
These tables and equations are all copied from the National Farm Building Code of Canada. The Code can be purchased online from the
Part 2 Structural Design
Table184.108.40.206. Minimum Specified Live Loads due to Use
|Type of Load||Minimum Specified Load|
|kPa||Load between Adjacent Aisles kN/m length of aisle|
|Cattle Tie Stall||Cow platforms, feed alleys||3.5||–|
|Cow traffic alleys (e.g. Litter alleys)||5.0||–|
|Milking Rooms and Milk Houses||2.5 (* the floor under a bulk milk tank shall be designed to support the load from the tank plus its contents)||–|
|Turkeys||2.0 (*Spaces under wire floors, slotted floors or cages shall have a minimum specified live load of not less than 1 kPa for each 100mm depth of manure)||–|
|Chickens||Housed without cages (including manure)||2.0||–|
|Housed in cages||2 levels of cage equipment with dropping boards||Chicken cage manufacturers should be consulted for information on the type and spacing of supports (floor stand or suspended type)
Bird mass is based on eight 1.8 kg birds for each 300mm length of deck. On this basis a 3-deck cage row has 24 birds in 300mm of cage row length.
Dropping boards used to prevent soiling on the lower level cages are assumed to accumulate 50mm of wet manure between cleaning operations.
|2 levels of cage equipment without dropping boards||1.4|
|3 levels of cage equipment with dropping boards||2.7|
|3 levels of cage equipment
without dropping boards
|4 levels of cage equipment with dropping boards||3.0|
Equipment Used for Manure Cleanout in a Poultry Barn
Where equipment up to 700kg including operator is used for manure cleanout in a poultry barn, the floor shall be designed for a two-wheel live load of 4.0 kN in addition to the distributed load of 1 kPa representing 100mm of wet litter.
Table 220.127.116.11. Floor Loads for Groups of Animals on Slotted Floors
|Livestock||Live Loads for Design of a Floor Slat, kN/m of slat||Distributed Live Loads for Design of Slotted floors and Their Supports,
|Dairy and Beef Cattle||4.5||5.0|
|Dairy and beef calves up to 150kg||2.2||2.5|
|Swine||Weaners up to 25kg||0.7||1.7|
|Feeders up to 100kg||1.5||2.5|
|Sows up to 225kg||2.5||3.5|
- Except as provided in sentence (2) the uniformly distributed live load on an area of floor used for farm machinery traffic shall not be less than 7.0 kPa
- Where it is anticipated that the area will be occupied by either loaded farm trailers and trucks or farm tractors having a mass in excess of 6 000kg, including the mass of mounted equipment, the live load shall be not less than 10 kPa.
- Concentrated love loads due to tractors and farm machinery shall not be less than 23kN per wheel, applied over an area of 750mm by 750mm, located to cause maximum effects.
- Where an area serves as a place for processing or for loading or unloading of vehicles, the minimum live loads for such areas shall be increased by 50% to allow for impact or vibration of the machinery or equipment.
Table A-18.104.22.168.B. Coefficients of friction for Grain and Silage
|Type of grain||Moisture Content % (wet basis)(1)||Smooth Steel µ||Corrugated Steel µ||Plywood µ||Concrete (2) µ||Internal Friction within the Grain, tan (3)|
|Wheat and Barley||11.0||0.1||0.35||0.3||0.35||0.5|
|High moisture ensiled grains, including ground shelled and ground ear corn||0.25-0.35(4)||0.35-0.45(4)|
(1) The moisture content of grain is the weight of water in the grain divided by the weight of the wet grain. For higher moisture contents, the friction coefficients will be appreciably higher, resulting in greater wall vertical loads, but maximum lateral pressures will occur with clean, dry grain.
(2) Values are for rough textured concrete. Where concrete is placed against smooth forms and polished by the repeated flow of grain, values will be approximately two-thirds of those shown.
(3) For horizontally corrugated or very rough surfaces, sliding my occur within the grain mass rather than on the surface, in which case the internal friction within the grain applies, if less than µ.
(4) For conservative design to resist lateral pressures, select the lower value of the range; for vertical friction force, select the higher value.
Table A-22.214.171.124.c. Ratio of horizontal to vertical pressure for grains and silages, k
|Type of Grain||Smooth Wall||Rough Wall|
|Flaxseed and canary seed||0.55||0.8|
|Whole -plant silages||0.4||0.4|
|High-moisture ensiled grains, including ground shelled and ground ear corn||0.5||0.5|
Storage for Dry Grains
- Pressures and loads for the design of storage for dry grains shall be determined by the analyses given in this article.
- In this article
F = maximum vertical load per unit of wall perimeter due to friction, kN/m
L = horizontal pressure against the bin wall, kPa,
Lb = horizontal pressure at the bottom of the vertical section of a bin wall
V = L/K = vertical pressure on the bin floor or within the grain mass, kPa
= coefficient of friction between the fill material and the bin wall (see table A-126.96.36.199.B.)
k = ratio of horizontal to vertical pressure (see table A-188.8.131.52.C.)
H = depth below surface of fill or where surface would be if fill was levelled, m
D = bin diameter, m
a = length of short side, m
b = length of long side, m
R = hydraulic radius
= D/4 for circular bins
= (2ab-a2)/4b for rectangular bins (long side)
= a/4 for rectangular bins (short side)
C = Reimbert coefficient
= bin wall slope measured from horizontal (see figure A-184.108.40.206.A.)
= bulk density kg/m3 (see Table A-220.127.116.11.A.)
g = acceleration due to gravity, 9.81m/s2
= 1.06g)/1000 = unit weight of material, kN/m3
= angle of internal friction
= angle of friction of fill material on bin wall = arc tan
e = natural log base = 2.71828
= hopper slope from horizontal
- In this Article a deep bin is defined as having a depth greater than 0.75 times the width and a shallow bin is defined as having a depth not greater than 0.75 times the width.
- Except as provided in sentences (7) and (8), the horizontal wall pressure in deep bins and in shallow bins with vertical walls shall be determined using the following Janssen formula:
- For shallow bins which have walls sloping at angles between 50o and 120o to the horizontal, the pressure normal to the wall surface shall be determined by multiplying the horizontal wall pressure calculated in Sentence (4) by the following Rembert coefficient
- The vertical friction load of the bin contents on the bin wall shall be determined from the following formula:
F = R (H-)
- For bins which empty through a central discharge opening, the horizontal wall pressure during emptying shall be that determined in Sentence (4) multiplied by an over pressure factor as given in Table 18.104.22.168 with values of C corresponding to H/4R between 2.5and 5 determined by linear interpolation. (See Appendix A.)
Overpressure Factors for Stored Grain
Forming Part of Sentence 22.214.171.124. (7)
|Grain Stored||Overpressure Factor|
|Cereal grains, shelled corn, soybeans and canola||1.0||1.4|
|Flaxseed and canary seed||1.0||1.6|
- For a bin which discharges through an opening which is eccentric by R/6 or more, the horizontal wall pressure during emptying shall be the pressure double on a strip of wall of width R extending from the discharge opening to the surface of the grain.
- The design vertical pressure for shallow bins with floors sloped 0o to 20o to the horizontal shall be V =
- The design vertical pressure for deep bins with floors sloped 0o to 20o to the horizontal shall be determined from the following Janssen equation:
- For bin bottoms sloped between 20o and 60o to the horizontal, the normal pressure which varies linearly from a maximum at the wall-hopper junction to a minimum at the projected apex of the hopper, shall be determined from the following equations.
P2 = Lb [sin2 +
Where P2 is the normal pressure at the top edge of the hopper, and P3 is the normal pressure at the apex of the projected hopper bottom.
- Bin bottoms sloped at 60o or greater shall be designed for mass flow. (See Appendix A.)
Table A-126.96.36.199 Bulk Densities of Agricultural Materials
|Grains and Seeds(1)||Alfalfa||750|
|Birds foot Trefoil||740|
|Turnip o Polish Rape||640|
|Husked Ear Corn||450|
|Rapeseed (see Canola)|
|Reed Canary Grass||380|
|Russian Wild Rye||250|
|Concentrated Feeds||Alfalfa Meal||250-350|
|Barley Ground Meal||380-450|
|Beet Pulp Dried||180-250|
|Brewers Grain Dry||220-290|
|Brewers Grain Wet||880-960|
|Corn Cobs Ground||270|
|Corn Cobs Whole||190-240|
|Corn Oil Cake||400|
|Flaxseed Oil Cake (Linseed Oil Cake)||770-800|
|Flaxseed Oil Meal (Linseed Oil Meal)||400-720|
|Malt Dry Ground||320-480|
|Soya Bean Meal||550-650|
|Roughage Feeds and Bedding||Hay(air-dried) Baled||160|
|Silage 70% moisture wet basis(2) tractor-packed in horizontal silo||700|
|Silage 70% moisture wet basis(2) unpacked in horizontal silo||500|
|Silage in tower silos see table (A-188.8.131.52.A.)|
|Straw Field Baled||130|
|Wood Shavings, Baled||320|
|Fruits and Vegetables||Apples, Bulk||600|
|Miscellaneous Products||Eggs in cases||200|
|Wool Compressed Bale||775|
|Wool Uncompressed Bale||200|
|Fresh Manure (feces and urine mixed)||1000|
Notes to Table A-184.108.40.206
- Bulk Densities for Grain given in Table A-220.127.116.11 are test weights determined by filling a small container. When grain is dropped some distance into a bin, a 5% increase in bulk density may occur. If a grain spreader is used during filling, the bulk density will be increased further, but wall pressures will be more uniform and slightly less than if filling from a central spout. This increase has been dealt with by the 1.06 factor in the definition of
- Bulk density at a moisture content other than 70% can be calculated as follows:
M= 30(70) / (100 – M)
M = bulk density at moisture content M%, kg/m3
70 = bulk density at 70% (wet basis), kg/m3
M = moisture content, per cent (wet basis)
Table A-18.104.22.168.A. Average Silage Density in Tower Silos (av) at typical Moisture Percentage (M), kg/m3
|Silo Diameter, m||Alfalfa M (%)||Corn Silage M (%)||Ground Shelled Corn, M(%)||Barley Silage, M(%)|