1、 ANSI/ASAE EP545 MAR1995 (R2015) Loads Exerted by Free-Flowing Grain on Shallow Storage Structures 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 agricul
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6、s, Engineering 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 p
7、rocess, consensus, 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 m
8、ajority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. CAUTION NOTICE: ASABE and ANSI standards may be revised or withdrawn at any time. Additionally, procedures of ASABE require that action
9、 be taken periodically 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/ASAE EP545 MAR1995 (R2015) C
10、opyright American Society of Agricultural and Biological Engineers 1 ANSI/ASAE EP545 MAR1995 (R2015) Approved February 1996; reaffirmed January 2015 as an American National Standard Loads Exerted by Free-Flowing Grain on Shallow Storage Structures Developed by the ASAE Loads Due to Bulk Grains, Fert
11、ilizers and Silage Subcommittee of the Structures Group; approved by the Structures and Environment Division Standards Committee; adopted by ASAE March 1995; approved as an American National Standard February 1996; reaffirmed by ASAE December 1999; reaffirmed by ANSI June 2000; reaffirmed by ASAE Fe
12、bruary 2005; reaffirmed by ANSI March 2005; revised editorially March 2005; reaffirmed by ASABE January 2010; reaffirmed by ANSI February 2010; reaffirmed by ASABE January 2015; reaffirmed by ANSI January 2015. Keywords: Grain, Loads, Pressure, Structures 1 Purpose 1.1 This Engineering Practice pres
13、ents methods of estimating the grain pressures within shallow storage structures used to store free-flowing, agricultural whole grains. 2 Normative References The following standards contain provisions which, through reference in this text, constitute provisions of this Engineering Practice. At the
14、time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Engineering Practice are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Standards organizations mai
15、ntain registers of currently valid standards. ANSI/ASAE D241.4 FEB93, Density, Specific Gravity, and Mass-Moisture Relationships of Grain for Storage 3 Terminology 3.1 Terms used in this Engineering Practice are defined as follows: 3.1.1 shallow storage structure: Grain storage with a square or rect
16、angular floor plan used to store grain where the width of the building is greater than 2 times the height of the grain at the wall. 4 Nomenclature k is ratio of lateral to vertical pressure, dimensionless; z is equivalent grain depth at a discrete point, m (ft); G is gravity acceleration constant, 9
17、.8 10-3 kN/kg (1.0 lbf/lb); ANSI/ASAE EP545 MAR1995 (R2015) Copyright American Society of Agricultural and Biological Engineers 2 H is total equivalent grain height, used to calculate resultant shear vertical and lateral forces acting on the wall, and floor pressure at the base of the wall, m (ft);
18、L(z) is lateral pressure at equivalent grain depth z, kPa (lbf/ft2); PHis resultant lateral force acting on the wall, kN/m (lbf/ft); PSis resultant shear force acting on the wall, kN/m (lbf/ft); V(z) is vertical pressure at equivalent grain depth z, kPa (lbf/ft2); W is bulk density of stored grain,
19、kg/m3 (lb/ft3); Y is height of grain on the wall, m (ft); is factor used to calculate total equivalent grain height, dimensionless (equation 2 and Table 1); is angle of repose of the grain, deg; is coefficient of friction of grain on structural surfaces, dimensionless; is internal angle of friction
20、for grain, deg. Table 1 Coefficient, , to determine the total equivalent grain height, H, for storages with sloping backfill Internal Angle of Friction, , deg Angle of Repose, , deg 16 18 20 22 24 26 28 30 24 1.15 1.17 1.19 1.22 1.25 - - - 26 1.16 1.19 1.22 1.25 1.28 1.31 - - 28 1.18 1.21 1.24 1.27
21、1.31 1.35 1.39 - 30 1.20 1.23 1.27 1.30 1.35 1.39 1.44 1.50 5 General Design Information 5.1 Total equivalent grain height. For conditions in which the top grain surface is not horizontal (sloping backfill condition), use the total equivalent grain height, H (see Figure 1). The total equivalent grai
22、n height can be determined by multiplying the actual grain depth at the wall by the appropriate coefficient, , from Table 1 or by using equation 2. =YH (1)()+=cossinsinYYH (2) 5.2 Equivalent depth of grain. The equivalent depth of grain, z, is shown in Figure 1. ANSI/ASAE EP545 MAR1995 (R2015) Copyr
23、ight American Society of Agricultural and Biological Engineers 3 Figure 1 Flat storage geometry 5.3 Bulk density. For design purposes a bulk density of 834 kg/m3 (52 lb/ft3) is recommended. This corresponds with the bulk density of wheat modified by a packing factor. For pressures imposed by grains
24、other than wheat, use bulk densities determined by the Winchester Bushel Test (USDA, 1980) or those listed in ANSI/ASAE D241, increased by packing factor of 1.08. 5.4 Ratio of lateral to vertical pressure. The ratio of lateral to vertical pressure, k, is assumed to be 0.5. 5.5 Internal angle of fric
25、tion. Suggested values of the internal angle of friction are given in Table 2. Table 2 Internal angle of friction for selected grains Grain Internal Angle of Friction, , deg Corn 27Wheat 27 Soybeans 295.6 Angle of repose. For free-flowing grains with a narrow range of particle sizes, the angle of re
26、pose can be assumed to be equal to the angle of internal friction. 5.7 Coefficient of friction between grain and wall material. Use values of the static coefficient of friction as given in Table 3. Table 3 Static coefficient of friction for selected grains on various wall surfaces Grain Steel Concre
27、te Corrugated Steel PlywoodCorn 0.25 0.35 0.50 0.44 Wheat 0.25 0.35 0.50 0.50Soybeans 0.25 0.35 0.50 0.38 ANSI/ASAE EP545 MAR1995 (R2015) Copyright American Society of Agricultural and Biological Engineers 4 5.8 Static pressures and dynamic pressures on walls and floors. (See Figure 1 and Figure 2)
28、Figure 2 Stresses on the structure and within the grain 5.8.1 Static vertical pressures. At a discrete point, z, the static vertical pressures, V(z), as estimated by a modified Coulombs equation are () WGzzV = (3)5.8.2 Static lateral pressures. To estimate the static lateral wall pressures, L(z), at
29、 a discrete point () ()zkVzL = (4)5.8.3 Vertical pressures on floor. The floor pressure next to the wall, V(H) is estimated by ()WGHHV =(5) 5.9 Resultant lateral and shear forces on the walls 5.9.1 Resultant lateral force. The resultant lateral force per unit length of wall, PH, is estimated by ()2H
30、HLPH= (6)5.9.2 Resultant shear force. The resultant shear force per unit length of wall, PS, is estimated by HSPP = (7)5.9.3 Dynamic pressures. Dynamic pressures are not considered to act on shallow storage structures; therefore, the pressures during loading and unloading are considered to be equal
31、to static pressures. 5.10 Special load considerations. Increased loads are caused by unbalanced loading conditions, by moisture or hygroscopic pressures, and by vibration induced pressures. No reliable methods exist to predict the magnitudes of increased loads caused by these factors. Factors of saf
32、ety shall be increased if the possibility of these loading conditions exists. ANSI/ASAE EP545 MAR1995 (R2015) Copyright American Society of Agricultural and Biological Engineers 5 6 Design Example The following example is provided to illustrate the design concepts presented in this Engineering Pract
33、ice: Initial design conditions: stored material, wheat; wall height, 4 m (13.12 ft); wall material, smooth galvanized steel. Step 1. Determine material properties: from 5.3, Bulk density equals 834 kg/m3(52 lbf/ft3); from Table 2, Internal angle of friction equals 27 deg; from Table 3, Coefficient o
34、f friction equals 0.25. Step 2. Calculate total equivalent grain height: read, from Table 1 (equation 2) assuming the angle of repose equals the internal angle of friction. Interpolating between the values for 26 deg and 28 deg, gives a value of 1.35 for . calculate total equivalent grain height usi
35、ng equation 2: H = Y = 4 1.35 = 5.4 m Step 3. Calculate static pressures: calculate static vertical pressure using equation 3: V(z) = WGz = 834 9.8 10-3 z = 8.2 z kPa calculate lateral pressures using equation 4: L(z) = kV(z) = 0.5 8.2z = 4.1 z kPa calculate vertical pressure on the floor using equa
36、tion 5: V(H) = WGH = 834 9.8 10-3 5.4 = 44.1 kPa Step 4. Calculate resultant wall forces: calculate resultant lateral force using equation 6: PH= L(H) H/2 = 4.1 H H/2 = 4.1 5.4 5.4/2 = 59.8 kN/m calculate the resultant shear force using equation 7: PS= PH= 0.25 59.8 = 14.9 kN/m ANSI/ASAE EP545 MAR19
37、95 (R2015) Copyright American Society of Agricultural and Biological Engineers 6 Annex A (informative) Commentary A.1 Pressures. Pressures are estimated using a modified Coulomb approach. Vertical pressures are assumed to be geostatic and vary linearly with respect to the height of material at any g
38、iven point. Lateral pressures are estimated based on the assumption that the wall supports a wedge of material. The wedge is bounded by the wall and the plane defined by the angle of internal friction (see Figure 1). The basic assumptions of this technique are the stored material is isotropic and ho
39、mogeneous and possesses internal friction; failure occurs along a plane surface; the material surface is planar; friction forces occur along the failure plane; the failure wedge is a rigid body; wall friction exists between the stored material and the wall; it is assumed that the wall is infinitely
40、long such that a unit length can be considered; the stored material is semi-infinite such that no interaction occurs between opposite walls. A.2 Total equivalent grain height. For a sloping backfill condition, an equivalent grain depth, H, must be calculated. The equivalent grain depth, H, is based
41、on lateral earth pressure theory for a vertical wall as assumed by Coulomb (Bowles, 1977). The equivalent grain depth, H, can be calculated using ()+=bYYHcossinsin(2)A.3 Equivalent depth of grain. To estimate grain pressures at discrete points the equivalent depth of grain, z, as shown in Figure 1 m
42、ust be used. This takes into account the effects of a sloping backfill condition. A.4 Bulk density. If a bin is used to store a variety of grains over its lifetime, it is recommended that it be designed for the storage of wheat. For wheat a bulk density of 834 kg/m3 (52 lb/ft3) is recommended. Value
43、s of bulk density for other grains are given in ANSI/ASAE D241. These values are based on standard tests and should be multiplied by a factor of 1.08 to account for the effects of compaction in a structure. Bulk density values determined by the Winchester Bushel Test (USDA, 1980) can be used in lieu
44、 of the values listed in ANSI/ASAE D241. A.5 Ratio of lateral to vertical pressure. The ratio of lateral to vertical pressure is assumed to be a constant value of 0.5 for all loading conditions and grains. A.6 Internal angle of friction. The internal angle of friction has an effect on the total equi
45、valent depth of grain, H, and the pressures estimated to occur within the structure. Values shown in Table 2 are average values of those normally found in the literature for free-flowing grains. The range of values found in the literature varies from 25 deg to 30 deg. Internal angles of friction for
46、 some oilseeds such as flaxseed and vetch may fall outside of this range. A.7 Angle of repose. For a sloping backfill condition the grain is assumed to stack at the angle of repose. The angle of repose has an effect on the total equivalent depth of grain, H, and the pressures estimated to occur with
47、in the structure. Gaylord and Gaylord (1984) and Bowles (1977) suggest that for free-flowing grains the internal angle of friction and the angle of repose are approximately equal. Kalman et al., (1993) have indicated that the angle of repose is influenced by the floor surface on which the material i
48、s being stacked. Pierce and Bodman (1987) conducted a field study in which piling angles of corn and milo were measured in round piles and flat storage buildings. Average piling angles of 23 and 29 deg were measured for corn and ANSI/ASAE EP545 MAR1995 (R2015) Copyright American Society of Agricultu
49、ral and Biological Engineers 7 milo, respectively. Pierce and Bodman indicated that moisture content of the grain did not appear to influence the piling angle of repose. Their values are approximately 4 deg smaller than those normally shown in the literature. Other sources in the literature indicate a moisture content effect on angle of repose. If the structure is filled by some mechanical technique which affects the st
