1、 ANSI/ASABE EP433 JUN00 (R2015) W/Corr. 1 Loads Exerted by Free-Flowing Grain on Bins American Society of Agricultural and Biological Engineers ASABE is a professional and technical organization, of members worldwide, who are dedicated to advancement of engineering applicable to agricultural, food,
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6、g Practices and Data approved after July of 2005 are designated as “ASABE“. Standards designated as “ANSI“ are American National Standards as are all ISO adoptions published by ASABE. Adoption as an American National Standard requires verification by ANSI that the requirements for due process, conse
7、nsus, and other criteria for approval have been met by ASABE. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but
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9、iodically to reaffirm, revise, or withdraw each standard. Copyright American Society of Agricultural and Biological Engineers. All rights reserved. ASABE, 2950 Niles Road, St. Joseph, Ml 49085-9659, USA, phone 269-429-0300, fax 269-429-3852, hqasabe.org ANSI/ASABE EP433 JUN00 (R2015) W/Corr. 1 Copyr
10、ight American Society of Agricultural and Biological Engineers 1 ANSI/ASAE EP433 JUN00 (R2015) W/Corr. 1 Approved September 1991; reaffirmed December 2015 as an American National Standard Loads Exerted by Free-Flowing Grain on Bins Developed by the ASAE Loads Due to Bulk Grains and Fertilizers Subco
11、mmittee of the Structures Group; approved by the Structures and Environment Division Standards Committee; adopted by ASAE December 1988; revised editorially February 1991, June 1991; approved as an American National Standard September 1991; reaffirmed December 1993, December 1994, December 1995, Dec
12、ember 1996, December 1997, December 1999; revised editorially March 2000; reaffirmed by ANSI June 2000; reaffirmed December 2001, March 2006, February 2011, December 2015; Corrigenda 1 added March 2016. Corrigenda 1 corrected publication error in equation 1 (4.1.1). Keywords: Bins, Grain, Grain bin,
13、 Loads, Pressure 1 Purpose 1.1 This Engineering Practice presents methods of estimating the grain pressures within centrally loaded and unloaded bins used to store free-flowing, agricultural whole grain. 2 Terminology 2.1 Terms used in this Engineering Practice are defined as follows: 2.1.1 antidyna
14、mic tube: A vertical conduit, generally at the center of a bin, with the bottom of the tube placed directly over an orifice through which grain can be unloaded from the bin. 2.1.2 bin: A container with a height to diameter (or shortest side) ratio greater than 0.5. 2.1.3 flume: A vertical tube attac
15、hed to the wall of a bin through which grain can flow. Discharge outlets may be placed in the bin wall at any location along the vertical rise of the conduit. 2.1.4 funnel flow: Flow from a bin in which all grain movement occurs through a central core with no movement occurring along the bin wall (s
16、ee Figure 1). 2.1.5 funnel flow hopper: A hopper in which a flow channel is formed within the stagnant grain (see Figure 2). 2.1.6 hopper: The sloped portion of a bin which is used to aid gravity discharge through an orifice. 2.1.7 mass flow hopper: A hopper in which all of the grain in the hopper i
17、s in motion whenever any grain is withdrawn through the hopper outlet (see Figure 2). 2.1.8 moisture induced or hygroscopic pressures: Pressures induced by expansion of grain resulting from increases in moisture content. 2.1.9 plug flow: Flow from a bin in which the grain moves out of the bin in a m
18、anner such that movement occurs along all or part of the bin wall (see Figure 1). ANSI/ASABE EP433 JUN00 (R2015) W/Corr. 1 Copyright American Society of Agricultural and Biological Engineers 2 2.1.10 thermally induced pressures: Pressures induced in a filled bin when subjected to a decline in ambien
19、t temperature. 2.1.11 vibration induced pressures: Pressures induced by ground or machinery vibrations. Figure 1 Bin flow patterns Figure 2 Hopper flow types ANSI/ASABE EP433 JUN00 (R2015) W/Corr. 1 Copyright American Society of Agricultural and Biological Engineers 3 3 Nomenclature a = length of th
20、e short side of a rectangular bin, m (ft) b = length of the long side of a rectangular bin, m (ft) c = equivalent bin wall length, m (ft) k = ratio of lateral to vertical pressure, dimensionless u = integration variable for equivalent material depth, m (ft); see Figure 3 D = bin diameter, m (ft); se
21、e Figure 3 F = overpressure factor, dimensionless G = gravity constant, 9.8 103kN/kg (1.0 lbf/lb) H = height of material from the lowest point of discharge to 1/3 of the height of the surcharge, if present, m (ft); see Figure 3 R = hydraulic radius of the bin (cross section area divided by perimeter
22、), m (ft) S = maximum shear stress between inclined surface and grain, kPa (lbf/ft2); see Figure 4 W = bulk density of stored grain, kg/m3(lb/ft3) Y = equivalent grain depth, m (ft); see Figure 3 Pv = vertical wall load per unit length of bin wall, kN/m (lbf/ft) Sv = shear stress between vertical wa
23、ll and grain, kPa (lbf/ft2) Vn = normal pressure on a surface inclined at an angle, , to horizontal, kPa (lbf/ft2); see Figure 4 L(Y) = lateral pressure of grain at depth, Y, kPa (lbf/ft2) V(Y) = vertical pressure of grain at depth, Y, kPa (lbf/ft2) = angle from horizontal to inclined surface, degre
24、es; see Figure 4 = coefficient of friction of grain on structural surfaces, dimensionless 4 General Design Information 4.1 Static pressures and dynamic pressures on bin walls and flat floors. 4.1.1 Static pressures. Estimate static pressures at depth, Y, by Janssens equation: ()=RkYekWRGYV 1(1) () (
25、)YkVYL = (2)4.1.1.1 Estimate the shear stress between the vertical wall and grain using equation 3: ANSI/ASABE EP433 JUN00 (R2015) W/Corr. 1 Copyright American Society of Agricultural and Biological Engineers 4 ()YLSv= (3) 4.1.1.2 Rectangular bins. To estimate the pressure next to the short side of
26、rectangular bins, use R = a/4 and for pressures next to the long side use R = c/4 where: baabc+=2(4)4.1.1.3 Conical surcharge. If a conical surcharge of grain is present at the top of the material mass, increase the grain depth, Y, by 1/3 of the conical surcharge height. 4.1.1.4 Bulk density. A maxi
27、mum of 834 kg/m3(52 lb/ft3) is recommended for the bulk density of any free-flowing grain. For pressures imposed by a specific commodity other than wheat, use bulk densities determined by the Winchester Bushel Test (USDA, 1980) or those listed in ASAE Data D241, Density, Specific Gravity and Weight-
28、Moisture Relationships of Grain for Storage, increased by a compaction factor of 1.08. Other material properties are those listed in Table 1. Table 1 Overpressure factors and material properties Wall Material k FSteel 0.30 0.5 1.4 Concrete 0.40 0.5 1.4Corrugated steel 0.37 0.5 1.4 4.1.2 Dynamic pres
29、sures 4.1.2.1 Funnel flow. Funnel flow bins have lateral wall pressures predictable by equation 2. Funnel flow will normally occur in bins which have H/D ratios less than 2.0. H is measured from the lowest point of discharge to the top of the grain surface, or if a surcharge is present, to 1/3 of th
30、e surcharge height (see Figure 3). Figure 3 Bin dimensions 4.1.2.2 Plug flow. Dynamic lateral wall pressures during plug flow are larger than those predicted by equation 2. Bins with an H/D ratio greater than 2.0 may unload by plug flow. Estimate lateral wall pressure in bins which ANSI/ASABE EP433
31、JUN00 (R2015) W/Corr. 1 Copyright American Society of Agricultural and Biological Engineers 5 unload by plug flow by the static pressure determined using equation 2 multiplied by an overpressure factor. Values of the overpressure factor, F, are given in Table 1. For flat bottom plug flow bins apply
32、this factor from the grain surface to within a distance of D/4 from the bottom. 4.1.2.3 Reductions in overpressure factor in bins which unload by plug flow. A reduction in the overpressure factor is allowed within a distance of D/4 from the base of flat bottom bins. Interpolate the overpressure fact
33、or between the value obtained from Table 1 at a height of D/4 to 1.0 at the bottom of the bin. 4.1.3 Calculation of vertical wall loads. Calculate vertical wall loads at depth, Y, from the following expression. ()RYVWGYPv= (5)4.1.4 Pressures on floors of flat bottom bins. Estimate vertical floor pre
34、ssures on flat bottom bins using equation 1. 4.2 Hopper pressures 4.2.1 Exclusions. This Engineering Practice does not apply to pressures in mass flow hoppers. 4.2.2 Load estimation techniques 4.2.2.1 Normal pressures. For pressure normal to an inclined hopper surface (see Figure 4). () () sincos22Y
35、LYVVn+= (6) To determine Vn at a discrete location within a hopper, determine V(Y) and L(Y) using equations 1 and 2 with equivalent grain depth, Y. Use the bin geometry at the intersection of the hopper and the bin wall to calculate hydraulic radius. Apply overpressure factors at the top of the hopp
36、er. Overpressure factors may be linearly reduced from F at the top of the hopper to 1.0 at the point of hopper discharge. Figure 4 Hopper stresses 4.2.2.2 Tangential stresses. For frictional stresses tangential to inclined hopper surface (see Figure 4). nVS =(7)ANSI/ASABE EP433 JUN00 (R2015) W/Corr.
37、 1 Copyright American Society of Agricultural and Biological Engineers 6 4.3 Pressures on antidynamic tubes and flumes 4.3.1 Lateral pressures on antidynamic tubes and flumes. Lateral pressures are exerted both internally and externally in a direction normal to the wall surface on an antidynamic tub
38、e or a flume. 4.3.1.1 External lateral pressures. The pressure at any given level on an antidynamic tube or flume is estimated as equal to the lateral pressure at the wall at the same level using the techniques described in Section 4.1. 4.3.1.2 Internal lateral pressure. The pressures on the wall at
39、 any given level in an antidynamic tube or a flume may be neglected or estimated using the techniques described in Section 4.1 with a bin diameter equal to the equivalent internal diameter of the antidynamic tube or the flume. 4.3.2 Vertical stresses on antidynamic tubes or flumes. Vertical stresses
40、 act on both internal and external surfaces of antidynamic tubes and flumes. 4.3.2.1 External vertical stresses. Estimate external stresses by multiplying the external lateral pressure at a given level on the antidynamic tubes and flume as estimated by the method described in Section 4.3.1.1 by an a
41、ppropriate coefficient of friction presented in Table 1. 4.3.2.2 Internal vertical stresses. Estimate internal stresses by multiplying the internal lateral pressure by the appropriate coefficient of friction from Table 1. 4.4 Special load considerations 4.4.1 Thermally induced pressures. Estimate th
42、ermal pressures for circular steel bins as 8% of the static load for temperature declines of 10C per hour and as 15% of the static load for temperature declines of 20C per hour. 4.4.2 Moisture induced or hydroscopic pressures 4.4.2.1 Magnitude. Moisture content increases during storage of 4% or more
43、 can cause lateral pressures to increase several times static load conditions. 4.4.2.2 Precautions. Precautions should be taken in the design, location and management of bins to prevent the occurrence of grain moisture content increases. 4.4.3 Vibration induced pressures. There are insufficient data
44、 available to predict the magnitude or significance of vibration induced pressures. 5 Commentary 5.1 This section includes the basis for the design methods suggested in Section 1 Purpose, Section 2 Terminology, Section 3 Nomenclature, and Section 4 General Design Information. Further discussion of t
45、he provisions of the Engineering Practice may be found in Bokhoven et al. (1986), Britton and Moysey (1986), Bucklin et al. (1986), Manbeck et al. (1986), and Ross et al. (1986). The methods described in this Engineering Practice apply only to bins which are centrally loaded and emptied. 5.1.1 Stati
46、c pressures. An accepted method of predicting static loads on bin walls and floors is that proposed by Janssen (1895). Janssen assumed that the bulk density, lateral to vertical pressure ratio, and coefficient of friction between the grain and bin wall were constants for any given configuration. Jan
47、ssens technique assumes that the grain pressure does not vary across the bin cross section. Values of k and listed in Table 1 and values of W listed in ASAE Data D241, Density, Specific Gravity, and Weight-Moisture Relationships of Grain for Storage, are values that will produce estimates of the upp
48、er bound grain pressures. 5.1.2 Dynamic pressures. Janssens equation was derived for static conditions. Under dynamic or plug flow conditions, forces are generated which are larger than those predicted using Janssens technique. ANSI/ASABE EP433 JUN00 (R2015) W/Corr. 1 Copyright American Society of A
49、gricultural and Biological Engineers 7 5.1.2.1 Funnel flow. Pressures can be predicted by Janssens equation in bins which empty by funnel flow. Material movement occurs in a center core of the mass, and overpressures are not generated. Studies of flow patterns in bins under 3 m (10 ft) in diameter indicate that the transition between funnel and plug flow may be at a point as low as H/D equal to 1.3 for small bins (Nguyen, 1980). However, field observation of bins over 3 m (10 ft) in diameter indicate that the t
