Document 1Qv0x5JqbQZLMG9076Q1m0pvq

AWWA C401-77 (Revision of AWWA C401-64) AWWA STANDARD PRACTICE for THE SELECTION OF ASBESTOS-CEMENT DISTRIBUTION PIPE, 4 IN. THROUGH 16 IN.. FOR WATER AND OTHER LIQUIDS First edition approved by AWWA Board of Directors Jan. 17, 1964. This edition approved May S, 1977. Q AMERICAN WATER WORKS ASSOCIATION 6666 West Quincy Avenue, Denver, Colorado 80235 CTD000228 Committee Personnel The Standards Committee on Asbestos-Cement Pressure Pipe, which reviewed and approved this standard, had the following personnel at the time of approval: R. S. Bryant, Chairman J. L. Warden, Vice-Chairman T. R. Gillen, Secretary Consumer Members S. C. Baker, Naval Facilities Engineering Command, Alexandria, VA* (NAVFAC) L. C. Bradley, Water Department. Fort Worth, TX (AWWA) P. J. Brady, Portsmouth Water Department, Portsmouth, VA (AWWA) R. S. Bryant, Department of Water and Power, Los Angeles, CA (ASCE) F. G. Denson, Works & Operations Department, Winnepeg, Manitoba (AWWA) R. Graff, Water Utilities, San Diego, CA ' (AWWA) J. E. Johnson,* U.S. Bureau of Reclamation, Denver, CO (BUREC) R. A. March and, Water Department, Warren, OH (AWWA) J. L. Warden, U.S. Bureau of Reclamation, Denver. CO (BUREC) General Interest Members G. C. Anderson, Insurance Services Office, New York, NY R. A. Barrows, C.E. Maguire, Inc., Waltham, MA V. R. Bickel, Department of Environmental Health, Albuquerque, NM S. L. Bishop,* Metcalf & Eddy, Boston, MA C. L. Frick,* Insurance Services Office, New York, NY R. S. Holmgren Jr., James M. Montgomery, La Jolla, CA F. A. Obert, Metcalf & Eddy, Boston, MA J. S. Slicer, Factory Mutual Research, Norwood, MA M. R. Suchomel, Underwriters Laboratories, Northbrook, IL W. Taggart, Wright-McLaughlin Engineering, Denver, CO (ISO) (NEWWA) (APWA) (NEWWA) (ISO) (AWWA) (WPCF) (FMR) (UL) (ASCE) Producer Members A. E. Alpine, Cement Asbestos Products Co., Birmingham, AL T. R. Gillen, Johns-Manville Sales Corp., Denver, CO J. C. Jackson, Asbestos-Cement Pipe Producers Association. Washington, D.C. A. I. Leff,* CertainTeed Products Corp., Valley Forge, PA W. R. Seipt, CertainTeed Products Corp., Valley Forge, PA D. W. Sullivan, Carlon, An Indian Head Co., Cleveland, OH * Alternate Copyright 1977 by American Water Works Assn. Printed in US ii (AWV A j (AW W A) (ACPPAj (AWW Aj (AWW A ) (AWW \) CTD000229 Table of Contents SEC. Foreword PAGE I. History of Standard ...................... iv II. Major Revisions.............................. iv Standard 1 General ..................................... 1.1 Scope .................................................. 1.2 References ......................................... 1 1 1 2 Pipe Design and Selection........ 2.1 Strength and Design Factors........ 2.2 Combined-Loading Theory ............ 2.3 Three-Edge Bearing Load Factors 2.4 Hydrostatic Pressures ................... 2.5 External Loads ................................. 2.6 Selection Curves ............................... 2 2 2 3 3 4 7 A ppendix A1 General ............................................. A2 Tables ............................................... 17 17 Tables 1 Typical Field Installation Conditions ..................................... 2 2 Correlation of Bedding Conditions, Pipe Size, and Load Factors ... 3 3 Impact Factors Caused by Moving Vehicles ......................... 7 4 Values of Load Coefficients for Concentrated and Distributed Superimposed Loads Centered Vertically Over Conduit ............ 8 SEC. PAGE 5 Values of Load Coefficients C. for Concentrated Superimposed Loads Centered Vertically Over Conduit ............................... 8 A1 Determination of Design Load w Applied in 3-Edge Bearing ........ 18 A2 Design Internal Pressure and Design Earth Load Intercepts for Use With Selection Curves .. 20 Figures 1 Load Pressure Curve ..................... 2 Crushing Test Assembly ............... 3 Graph for Determining Load Coefficient Values ....................... 4 Graph for Determining Ca Coefficients .................................... 5 Concentrated Superimposed Load .. 6 Distributed SuperimposedLoad ... 7 Selection Curves for 4-in. Asbestos-Cement Pipe .......... 8 Selection Curves for 6-in. Asbestos-Cement Pipe ......... 9 Selection Curves for 8-in. Asbestos-Cement Pipe .......... 10 Selection Curves for 10-in. Asbestos-Cement Pipe .......... 11 Selection Curves for 12-in. Asbestos-Cement Pipe .......... 12 Selection Curves for 14-in. Asbestos-Cement Pipe .......... 13 Selection Curves for 16-in. Asbestos-Cement Pipe .......... A1 Earth Load Conditions ................... A2 Bedding Conditions Illustrated.... 3 3 5 6 7 7 10 11 12 13 14 15 16 17 17 iii CTD000206 Foreword This forcioord is for information only and is not a part of .1IVIVA C401. I. History of Standard The information contained in this standard was first published as, "AWWA Handbook H2." with AWWA Board of Directors approval on Jan. 27. 1964. The designation was changed later to. "AWWA C401-64." Originally, it covered sizes 4--36 in. although the design was primarily based on service conditions generally related with smaller (4-16 in.) distri bution sizes. In the smaller diameters the effect of water hammer generated by the opening and closing of fire hy drants can be of significant magnitude because of the high velocities gener ated by open hydrant flow conditions on small diameter lines in distribution systems. It is difficult to evaluate ac curately the magnitude of surges, and if calculated, it would be impractical to attempt to control the surge by the use of surge tanks or other devices. Rather than employ a rule-of-thumb surge allowance based upon an as sumed velocity change, a large factor of safety is applied to the class pres sure rating of the pipe to take into account the undetermined surges. AWWA C403, "Standard Practice for the Selection of Asbestos-Cement Transmission and Feeder Main Pipe. 18 in. Through 42 in.,'' is a standard containing information similar to that contained herein but dealing with larger diameter pipes. In AWWA C403 the design is based on evaluation of all design conditions including surge pressures. Also, adequate factors of safety are applied to the combination of pressures to which the pipe line will be subjected. The primary difference between AWWA C401 and AWWA C403 is one of differing methods for designing pipelines to account for surge pres sures. In the small sizes where surges can be of great magnitude and are im practical to control, a large factor of safety is employed to compensate for the unknown. In the large sizes the design is based upon a more detailed evaluation of the magnitude of surge pressures, and a factor of safety based upon a more precise knowledge of ac tual operating conditions is employed. II. Major Revisions Major changes to the 1964 edition of this standard made in this revision are: 1. The title has been changed to in dicate that the pipe is intended for use in distribution systems. 2. The size range has been changed to limit the maximum size covered by this standard to 16-in. diameter pipe. 3. Figure 2. Crushing Test Assem bly, has been changed to show the C dimension to be approximately 1 in./ft of internal pipe diameter but in no case less than 1 in. IV CTD000207 American Water Works Association AWWA C401-77 (Revision of AWWA C401-64) AWWA Standard Practice for The Selection oi Asbestos-Cement Distribution Pipe, 4 in. Through 16 in., for Water and Other Liquids Section 1--General Sec. 1.1--Scope Sec. 1.2--References This standard has been prepared so that design engineers can quickly de termine the correct class of asbestoscement pipe to use under various com binations of internal pressure and ex ternal loading. Curves are included to expedite the selection of the correct class of pipe. Detailed analyses of the various structural factors affecting pipe design and selection are treated under separate headings. 1.1.1 Pressure classes. Pipe pres sure class designations of 100, 150, and 200 refer to the similarly numbered classes specified in AWWA C400, "Standard for Asbestos-Cement Dis tribution Pipe, 4 in. Through 16 in., for Water and Other Liquids." 1.1.2 Installation. Detailed coverage of the installation of asbestos-cement pipe can be found in AWWA C603, "Standard for the Installation of As bestos-Cement Pressure Pipe." This standard references the follow ing documents. They form a part of this standard to the extent specified herein. In any case of conflict, the re quirements of this standard shall pre vail. 1. Schlick, W.J. Supporting Strengths for Cast-Iron Pipe for Wa ter and Gas Service, Iowa State Col. Eng. Sta. Bull., No. 146 (Jun. 1940). 2. ASCE. Design and Construction of Sanitary and Storm Sewers, Man ual of Engineering Practice No. 37, Am. Soc. Civ. Engrs., New York (1967). 3. Kerr, S.L. Practical Aspects of Water Hammer, Jour. AWWA, 40: 699 (Jun. 1948). 4. Marston, Anson. The Theory of External Loads on Closed Conduits in the Light of Latest Experiments, Iowa State Coll. Eng. Exp. Sta. Bull.. No. 96 (1930). l CTD000208 2 A-C DISTRIBUTION' PIPE Section 2--Pipe Design and Selection Sec. 2.1--Strength and Design Factors The strength of asbestos-cement water pipe must be sufficient to with stand the combined forces of internal hydrostatic pressure and external loads. Furthermore, the conditions under which the pipe is installed will have a direct relationship to its ability to re sist these forces. Therefore, satisfac tory pipe performance in field service requires that the bedding conditions, as well as the internal and external forces acting on the pipe, be taken into consideration when selecting a class of pipe for any given installation. Finally, sound engineering practice requires that adequate safety factors be applied to strength requirements to ensure per formance under less than ideal condi tions. 2.1.1 Bedding conditions. The bed ding conditions described in Table 1 have been selected as representative of typical installation conditions encoun tered in the field. They are illustrated in Fig. A2 in the appendix. TABLE 1 Typical Field Installation Conditions 2.1.2 Safety factors. In the selec tion curves, a safety factor of 4.0 is applied to the operating pressure and a safety factor of 2.5 is applied to earth loads. Furthermore, pipe selected from the curves will have a safety factor of at least 2.5 for the operating pressure when combined with a safety factor of 2.5 for resisting an earth load consist ing of the total equivalent earth load plus a 10 000-lb wheel load and impact load. Under impact loading condi tions, the 2.5 safety factor for the op erating pressure represents sound de sign practice, for it is unlikely that internal surge pressure would occur at the same instant as external impact. Sec. 2.2--Combined-Loading Theory Tests of asbestos-cement pipe under various combinations of internal pres sure and external load applied in threeedge bearing (see Sec. 2.3) indicate that there is a relationship between the combined loads at the point of pipe fracture. This relationship can be rep resented by a parabolic curve as shown in Fig. 1. The equation for the load pressure parabolic curve shown in Fig. 1 may be expressed as: Bedding Condition Class Description A Gravel or sand base, backfill tamped B Same as A but backfill not tamped C Pipe laid on earth mounds or pipe barrel on fiat trench bottom with excavated cou pling holes, backfill tamped D Same as C but backfill not tamped in which, P is the internal pressure, in pounds per square inch, that will burst the pipe when no external load exists; W is the external load, in pounds per lineal foot of pipe in the three-edge bearing test, that will crush the pipe when no internal pressure exists; p is the internal pressure, in pounds per square inch which, in combination with some external load w applied in three- CTD000209 DESIGN AND SELECTION P 3 p P represents the internal pressure; W the external load. edge bearing, will fracture the pipe; and w is the external load, in pounds per lineal foot of pipe applied in threeedge bearing which, in combination with some internal pressure p, will fracture the pipe. The diagram at the left shou's a side view of the test assembly; that at the right, an end view. P represents load; R, approximately 0.5 in.--the radius of the bearings; D, the nominal diameter of the pipe; and C, the clear space bctzvecn sup ports. C should be approximately 1 in./ft of internal pipe diameter but in no case less than 1 in. TABLE 2 Correlation of Bedding Conditions, Pipe Size, and Load Factors Sec. 2.3--Three-Edge Bearing Load Factors A convenient method of testing pipe for crushing strength W is the threeedge-bearing method of loading shown in Fig. 2. Because the field supporting strength of a conduit is influenced by the bedding conditions and the lateral pressure acting against the sides of the conduit, it is necessary to apply a load factor to the three-edge bearing loads in order to correlate them to the field loads. Since the external load equals the load factor times the three-edge bearing load, the load factor equals the external load divided by the three-edge bearing load. Table 2 shows load fac tors to be applied for each of the bed ding conditions described in Table 1. Bedding Class A B C D Pipe Size in, 4-12 14-16 4-16 4-12 14-16 4-16 Load Factor 1.7 1.8 1.5 1.3 1.4 1.1 Sec. 2.4--Hydrostatic Pressures The hydrostatic pressures to be con sidered in pipeline design are static operating pressure and surge pressure. The static pressure will be fixed by the particular field service condition. Or dinary surge pressure conditions are allowed for in this standard by apply ing a safety factor of at least 4.0 to internal pressure in combined loading. CTD000210 4 A-C DISTRIBUTION PIPE 2.4.1 Exceptional surge pressures. When exceptional surge pressures are a necessary specific consideration in design, a conservative basis for surge allowance determination is the method proposed by S. Logan Kerr. His method considers the fundamental re lations affecting water hammer, includ ing velocity of flow in the pipeline, length of the pipeline, time of valve operation or interruption of flow, and the pressure wave velocity. Water hammer allowance is determined by the formulas of Eq 2 and 3. in which, h is the water hammer allowance, in feet; p is the water hammer allowance, in pounds per square inch; a is the velocity of the pressure wave, in feet per second; g is the acceleration due to gravity (32.2 fps/s) ; and V is the flow line velocity, in feet per second, cut off by the valve operation or other action in the critical time, or less. in which, a is the pressure wave velocity in feet per second; k is the modulus of compression of water, in pounds per square inch (290 000-300 000 psi) ; E is the modulus of elasticity of asbes tos-cement pipe, in pounds per square inch (3 400 000 psi) ; d is the internal diameter, in inches; and e is the wall thickness, in inches. Sec. 2.5--External Loads External-load determinations for un derground conduit used in this stan dard are based on the data in Chapter 9 of the Manual on Design and Con struction of Sanitary and Storm Sew ers produced jointly by ASCE and WPCF. External loads on conduit are of two types : (1) those due to gravitv earth loads and (2) those due to su perimposed loads that may be static or moving. 2.5.1 Gravity earth loads. The mag nitude of gravity earth loads may be computed by using the theory devel oped by Anson Marston which states, in general, that the load on a buried conduit is equal to the weight of a prism of earth (called the interior prism) directly over the conduit plus or minus the frictional shearing forces transferred to that prism by the adja cent prisms of earth. The magnitude and direction of these frictional forces are a function of the amount of relative settlement occurring between the inte rior and adjacent earth prisms. The general form of Marston's equation is W = CwB Eq t in which, W is the vertical load, per lineal foot, acting on the conduit because of gravity earth loads; w is the weight of earth, in pounds per cubic foot; B is the trench or conduit width, depending on installation conditions; and C is the coefficient that includes the effect of: 1. The ratio of the height of the fill to the width of the trench or conduit. 2. the shearing forces between the interior and adjacent earth prisms, 3. the direction and amount of rela tive settlement between interior and adjacent earth prisms for embankment conditions, and 4. the rigidity of conduit support for embankment conditions. 2.5.1.1 Values for external loads may be determined by Marston's for- CTD0002H DESIGN AND SELECTION 5 0 10 20 30 40 50 60 70 Coefficient -Ce Tig. 3. Graph for Determining Load Coefficient Values The graph, shows a plot of load coefficient values Cc against values obtained by dividing . the height of the fill above the conduit by the outside ividth of the conduit H/Bc. mula as shown in Eq 5. Tables of external loads based on soil weight of 120 lb/cu ft are presented in Table A1 in the appendix. Wc = C'w(Bc)1 Eq 5 in which, Wc is the load on the conduit, in pounds per lineal foot; w is the unit weight of the soil, in pounds per cubic foot; Bc is the outside width of con duit, in feet; and Cc is the load co efficient. In this formula load coefficient Cc is a function of H/Bc, p, rsd, g, and k. H is the height of the fill above the conduit, in feet. The projection ratio p is the ratio of the distance of the top of the conduit above the natural grade to the width of the conduit. rsd is the settlement ratio, g is the coefficient of internal friction of the backfill mate rial, and k is the Rankins ratio of lat eral pressure to vertical pressure. 2.5.1.2 Based on a Class C flatbottomed. backfill-tamped trench, con servative values of p = 1.0, rsdp = 0.70, and kg. = 0.192 were used in the deter mination of external loads for the per formance curves. Cr values may be determined from Fig. 3, which shows a plot of Cc against H/Bc ratios. For values of H/Bc greater than 1.3, when rsdp -- 0.70, the graph is linear and values may be determined by the em pirical equation Cc = 1.892 ^ - 0.96 Bc Eq 6 2.5.1.3 Occasionally, a trench con dition exists in which the width of the trench is less than two or three times the widths of the conduit. In such cases, Marston's trench condition for mula may be used for determinations of the gravity loads. Wd = Cdw(BiY Eq 7 in which, Wd is the vertical load, in pounds per lineal foot; Bd is the width of the trench; w is the weight of the backfill soil in pounds per cubic foot, and C4 is a load coefficient. (See Fig. 4 for values of Cd.) CTD000212 6 A-C DISTRIBUTION PIPE Fig. 4. Graph for Determining Od Coefficients Each of the above curves represent Cd values for k/* and k^'. A represents 0.1024 for granular materials without cohesion; B is 0.165 maximum for sand and gravel; C is 0.150 maximum for saturated top soil; D, 0.13 maximum for ordinary clay; and E, 0.110 maximum for saturated clay. The symbol jt.', is the coefficient of friction be tween the backfill material and the sides of the ditch. 2.5.2 Superimposed loads. Where unusually heavy superimposed loads or impact loads are present, the solution of their magnitude may be computed for either a concentrated load (such as a truck load) or a distributed load condition. Normal truck and accom panying impact loads need not be con sidered when the depth of the cover is greater than 6 ft. 2.5.2.1 Concentrated load. The mag nitude of a superimposed load pro duced by a concentrated load (see Fig. 5) is determined by use of the formula PF W,c = C, -- Eq 8 in which, is the load on the conduit, in pounds per lineal foot; P is the con centrated load, in pounds; F is the im pact factor used to allow for the effects CTD000213 DESIGN AND SELECTION 7 Fig. 6. Distributed Superimposed Load D and M are the width and length, in feet, respectively, of the area over which the distributed load acts. The uniform load is lbs per sq ft acting on area D X M. P represents the concentrated load; H, the height from the top of the conduit to the ground surface; Bc, the width of the conduit; and L. the length of the conduit. TABLE 3 Impact Factors Caused by Moving Vehicles Type of Traffic Impact Factor F of dynamic loads due to moving ve hicles (see Table 3) ; C, is a load co efficient, a function of BC/2H and L/2H (see Tables 4 and 5); Br is the width of the conduit, in feet (OD of the pipe) ; H is the height from the top of the conduit to the ground surface, in feet; and L is the effective length of the conduit, in feet. L is 3 ft for conduits greater than or equal to 3 ft in length, but is the actual length for conduits less than 3 ft in length. 2.5.2.2. Distributed load. In the case of a distributed superimposed load, the formula may be written in the form of Highway Railway Airfield runways. taxiways, aprons, or hardstands 1.50 1.75 1.00 1.50 impact factor (see Table 3) ; Bc is the width of conduit, in feet; C, is a load coefficient, a function of D/2H and M/2H (see Table 4) ; H is the height from the top of the conduit to the ground surface, in feet; and D and M are the width and length, respectively of the area over which the distributed load acts, in feet. W,d = CspFBc Eq 9 Sec. 2.6--Selection Curves in which, IITd is the load on the conduit, in pounds per lineal foot (see Fig. 6) ; p is the intensity of distributed load, in pounds per square foot; F is the Research tests and the application of statistical analysis have shown that as bestos-cement pipe strength may be graphically illustrated by combinedloading parabolic curves. The com- CTD000214 8 A-C DISTRIBUTION PIPE TABLE 4 Values of Load Coefficients for Concentrated and Distributed Superimposed Loads Centered Vertically Over Conduit domr 0.! 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.5 2.0 hi L mmTs O.t 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.5 2.0 5.0 0.019 0.037 0.053 0.067 0.037 0.072 0.103 0.131 0.053 0.103 0.149 0.190 0.067 0.131 0.190 0.241 0.079 0.155 0.224 0.284 0.089 0.174 0.252 0.320 0.097 0.189 0.274 0.349 0.103 0.202 0.292 0.373 0.108 0.211 0.306 0.391 0.112 0.219 0.318 0.405 0.117 0.229 0.333 0.425 0.121 0.238 0.345 0.440 0.124 0.244 0.355 0.454 0.128 0.248 0.360 0.460 0.079 0.089 0.097 0.103 0.155 0.174 0.189 0.202 0.224 0.252 0.274 0.292 0.284 0.320 0.349 0.373 0.336 0.379 0.414 0.441 0.379 0.428 0.467 0.499 0.414 0.467 0.511 0.546 0.441 0.499 0.546 0.584 0.463 0.524 0.584 0.615 0.481 0.544 0.597 0.639 0.505 0.572 0.628 0.674 0.525 0.596 0.650 0.703 0.540 0.613 0.674 0.725 0.548 0.624 0.688 0.740 0.108 0.112 0.117 0.121 0.124 0.211 0.219 0.229 0.238 0.244 0.306 0.318 0.333 0.345 0.355 0.391 0.405 0.425 0.440 0.454 0.463 0.481 0.505 0.525 0.540 0.524 0.544 0.572 0.596 0.613 0.574 0.597 0.628 0.650 0.674 0.615 0.639 0.674 0.703 0.725 0.647 0.673 0.711 0.742 0.766 0.673 0.701 0.740 0.774 0.800 0.711 0.740 0.783 0.820 0.849 0.742 0.774 0.820 0.861 0.894 0.766 0.800 0.849 0.894 0.930 0.784 0.816 0.868 0.916 0.956 TABLE 5 Values of Load Coefficients C. for Concentrated Superimposed Loads Centered Vertically Over Conduit in. 2 2.5 3 4 5 6 8 10 12 16 20 4 0.105 0.076 0.055 0.033 0.022 0.016 0.009 0.006 0.004 0.002 0.0015 6 0.147 0.106 0.078 0.046 0.031 0.023 0.013 0.008 0.006 0.003 0.002 8 0.191 0.137 0.102 0.061 0.041 0.029 0.017 0.010 0.008 0.004 0.003 10 0.237 0.174 0.129 0.078 0.052 0.037 0.022 0.013 0.009 0.006 0.0035 12 0.279 0.202 0.153 0.092 0.062 0.044 0.025 0.016 0.011 0.007 0.004 14 0.317 0.232 0.175 0.106 0.071 0.050 0.030 0.018 0.013 0.008 0.005 16 0.354 0.259 0.197 0.121 0.081 0.057 0.034 0.021 0.015 0.009 0.0055 bined-loading theory developed by the late W.J. Schlick is used as the basis for selection curves for asbestos-ce ment water pipe. 2.6.1 Curve development. The se lection curves included in this standard were developed using the load-pressure formula, with the external load inter cept being the external load as tabu lated in Table 2 of AWWA C400-77, "Standard for Asbestos-Cement Dis tribution Pipe, 4 in. Through 16 in., for Water and Other Liquids," and the design point on the parabolic curve being that condition existing at a 5-ft depth of cover with the trench width assumed as pipe ID plus 2 ft, a bed ding condition of Class C and a soil weight of 120 lb/cu ft. The external loads were based on the positive pro jecting conduit analysis because this analysis produced the governing load on the pipe at the conditions pre viously set forth. The design point for each class of pipe is based on a safetyfactor of 4 times the pipe pressure class and 2.5 times the three-edge bear ing equivalent of the trench load. Once the parabolic curve has been estab lished through the external load mter- CTD000215 DESIGN AND SELECTION 9 cept and the control point, the equiv alent depth of cover scale is correlated for the various bedding conditions uti lizing either the trench load condition or the positive-projecting conduit-load condition, whichever is the governing load condition. 2.6.2 Curve use. The curves may be used conveniently by entering them through the depth of cover and bed ding condition scales. The scales are correlated to the three-edge bearing equivalents of the design external loads with a safety factor of 2.5. When there is an external loading condition different from that due only to depth of cover, or when conditions warrant a change in the safety factor, the equivalent external load should be de termined and the selection curve en tered at the proper value on the design external load scale. The field support ing strength listed for pipe so selected has been proved conservative during many years of performance under var ious field conditions. 2.6.2. Example. The application of the curves to design is shown in the following problem: Required: A 6-in. pipe to operate at a pressure of 120 psi at 8 ft depth of cover. Bedding condition Class C. soil weight 120 lb/cu ft. Solution: Enter the selection curve for 6-in. pipe at bedding condition Class C, 8 ft cover. The intersection of the 8-ft cover line with the 120 psi operating pressure line falls between pipe Classes 100 and 150. Use 6 in., Class 150. The intersection of the 8-ft cover line with the Class 150 curve is at 135 psi operating pressure, or 550 psi de sign pressure. Therefore, the pressure safety factor equals 550/120 = 4.6. with a safety factor of 2.5 for external load. 2.6.3 Curves. The selection curves for 4 in. through 16 in. asbestos-ce ment pipe are shown in Figs. 7 through 13 respectively. CTD000216 10 A-C DISTRIBUTION' PIPE 1,000 Design External Load-lb/lin ft 2,000 3,000 4,000 5,000 1,000 800 Design P ressure-psi 600 400 9 200 Operating Pressure Bedding Conditions CTD000217 DESIGN AND SELECTION Design External Load-lb/lln ft 11 Design Pressure - p s i Operating Pressure psi- Bedding Conditions Fig. 8. Selection Curves for 6-in. Asbestos-Cement Pipe CTD000218 12 0 A-C DISTRIBUTION PIPE 2,000 Design External Load-lb/lin ft 4,000 6,000 8,000 10,000 Design P ressure-psi Operating P ressure-psi Bedding Conditions CTD000219 DESIGN AND SELECTION Design External Load -- Ib/iin ft 13 Design P ressure-psi Operating P ressure-psi Bedding Conditions Depth of Cover-ft Fig. 10. Selection Curves for 10-in. Asbestos-Cement Pipe CTD000220 Design P ressure-psi Operating Pressure psi- 14 A-C DISTRIBUTION PIPE Design External load-lb/lin ft Fig. 11. Selection Curves for 12-in. Asbestos-Cement Pipe CTD000221 Bedding Conditions DESIGN AND SELECTION Design External Load-lb/lin ft 15 Design Pressure - p s i Operating P ressure-psl Bedding Conditions Fig. 12, Selection Curves for 14-in. Asbestos-Cement Pipe CTD000222 Operating P JitssaJd.idisea 16 A-C DISTRIBUTION PIPE Design External Load-lb/lin ft rig. 13. Selection Curves for 16-in. Asbestos-Cement Pipe CTD000223 Bedding Conditions APPENDIX Appendix 17 This appendix is for information only and is not a part of AlCH'A C401. Al. General Data developed for the preparation of the selection curves are included in this appendix. Figures illustrating the various bedding conditions and the earth load conditions used in the prep aration of the selection curves are in cluded. in the tables, and for Class 200 pipe, the loads would be greater. The max imum variation would be less than 5 per cent. A2. Tables In Table A2 of design internal pres sure and design external load inter cepts. the external loads are the crush ing loads that the pipe must be able to support without failure as specified in AVVW'A C400. The tables of design earth load zv for various field bedding conditions and depths of cover show the calculated loads for Class 150 pipe. For Class 100 pipe, similar calculated loads would be less than those shown Fig. A2. Bedding Conditions Illustrated Fig. Al. Earth Load Conditions The illustration on the left shows trench conduit conditions, that is, the trench width is less than two or three times Bc. The illustration on the right shozes a pos itive projecting conduit condition, that is, the trench width is .greater than tzeo or three tunes Bc. The shaded area repre sents backfill. Class A bedding conditions are shown in (a) and (b). Class C conditions are shown in (c) and (d). In all four di agrams, the lightly shaded area represents approved backfill, not frozen and free from lumps, large stones, boulders, or other unsuitable substances. The heavily shaded areas represent approved backfill, carefully compacted in 4-in. layers as specified by the engineer, hi (a), a min imum of 2 in. of sand is placed in a shaped bottom under the pipe, hi lb), the pipe is bedded in a graz'd base, hi (c), the pipe barrel rests on earth mounds and then the backfill bctzeccii the earth mounds is compacted, hi (d>. the pipe barrel is resting on the fiat bottom of the trench. Class B condition is the same as Class A, and Class D i.r the same as Class C except that the backfill is not tamped in B or D. CTD000224 18 A-C DISTRIBUTION' PIPE TABLE A1 Determination of Design Earth Load w Applied in 3-Edge Bearing 12 31 2 3l 2 3 w ww Earth Earth Earth Pipe Size in. Ex ternal Load lb Equivalent Load Three-Edge Applied in Bearing Load Three-Edge { Col t \ Bearing \Load Factor/ (Col. 2X2.5 Ex ternal Load /& Equivalent Load Three-Edge Applied in Bearing Load Three-Edge / Col. 1 \ Bearing VLoad Factor/ (Col. 2X2.5 Ex ternal Load lb Equivalent Load Three-Edge A pplied in Bearing Load Three-Edge / Cd.1 Hearing \Load Factor/ (Col. 2X2.5 Factor of Factor of Factor of Safety) Safety) Safety) Class A Bedding Condition 2.5 ft of Cover 5 ft of Cover 4 219 6 297 8 371 10 450 12 507 14 559 16 604 129 175 218 264 298 311 335 323 458 438 634 545 814 660 1,012 745 1,174 778 1,336 838 1,484 269 373 479 595 691 742 825 673 933 1,198 1,488 1,728 1,855 2,063 12 ft of Cover 16 ft of Cover 4 1,127 6 1,584 8 2,051 10 2,451 12 2,678 14 2,886 16 3,130 663 932 1,206 1,441 1,575 1,603 1,738 1,658 2,330 3,015 3,603 3,938 4,008 4,345 1,510 2,124 2,602 2,835 3,078 3,367 13,663 888 1,249 1,531 1,668 1,811 1,870 2,035 2,220 3,123 3,828 4,170 4,528 4,675 5,088 8 ft of Cover 744 1,041 1,344 1,688 1,975 2,267 2,398 438 612 790 993 1,162 1,259 1,332 1,095 1,530 1,975 2,483 2,905 3,148 3,330 20 ft of Cover 1,893 2,550 2,816 3,076 3,402 3,727 4,063 1,113 1,500 1,656 1,809 2,001 2,070 2,257 2,783 3,750 4,140 4,523 5,003 5,175 5,643 Class B Bedding Condition 2.5 ft of Cover 4 219 6 297 8 371 10 450 12 507 14 559 16 604 146 198 248 300 338 373 402 365 495 620 750 845 933 1,005 12 ft of Cover 4 1,127 6 1,584 8 2,051 10 2,451 12 2,678 14 2,886 16 3,130 751 1,056 1,367 1,634 1,785 1,924 2,086 1,878 2,640 3,418 4,085 4,463 4,810 5,215 5 ft of Cover 458 634 814 1,012 1,174 1,336 1,484 305 423 542 674 783 890 989 763 1,058 1,355 1,685 1,958 2,225 2,473 16 ft of Cover 1,510 1,224 2,602 2,835 3,078 3,367 3,663 1,007 1,416 1,735 1,890 2,052 2,244 2,442 2,518 3,540 4,338 4,725 5,130 5,610 6,105 8 ft of Cover 744 1,041 1,344 1,688 1,975 2,267 2,398 496 694 896 1,126 1,317 1,512 1,598 1,240 1,735 2,240 2,815 3,293 3,780 3,995 20 ft of Cover 1,827 2,550 2,816 3,076 3,402 3,727 4,063 1,218 1,700 1,877 2,050 2,268 2,485 2,708 3,045 4,250 4,693 5,125 5,670 6.213 i 6,770 CTD000225 APPENDIX 19 TABLE hi--Determination of Design Earth Load w Applied in 3-Edge Bearing {contd.) 12 31 2 31 2 3 Pipe Size m. Ex ternal Load lb w Earth Equivalent Load Three-Edge Applied m Bearing Load Three-Edge / C<3.1 \ Bearing \Load Factor/ (Col. 2X2.5 Factor of Ex ternal Load lb Equivalent Three-Edge Bearing Load : / Col. 1 \ \Load Factor/ w Earth Load Applied in Three-Edge Bearing (Col. 2 X 2.5 Factor of Ex ternal Load lb w Equivalent Three-Edge Bearing Load / Col 1 \ Earth Load Applied in Three-Edge Bearing \Load Factor/ (Col. 2X2.5 Factor of Safety) Safety) Safety) Class C Bedding Condition 2.5 ft of Cover 4 219 6 297 8 371 10 450 12 507 14 559 16 604 168 228 286 346 390 400 431 420 570 715 865 975 1,000 1,078 12 ft of Cover 4 1,127 6 1,584 8 2,051 10 2,451 12 2,678 14 2,886 16 3,130 867 1,219 1,578 1,885 2,060 2,061 2,235 2,168 3,048 3,945 4,713 5,150 5,153 5,588 5 ft of Cover 458 634 814 1,012 1,174 1,336 1,484 352 488 626 778 903 954 1,060 880 1,220 1,565 1,945 2,258 2,385 2,650 16 ft of Cover 1,510 2,124 2,602 2,835 3,078 3,367 3,663 1,161 1,634 2,002 2,181 2,368 2,405 2,616 2,903 4,085 5,005 5,453 5,920 6,013 6,540 8 ft of Cover 744 1,041 1,344 1,688 1,975 2,267 2,398 573 801 1,034 1,299 1,519 1,619 1,712 1,433 2,003 2,585 3,248 3,798 4,048 ' 4,280 20 ft of Cover 1,893 2,550 2,816 3,076 3,402 3,727 4,063 1,456 1,961 2,166 2,366 2,617 2,662 2,902 3,640 4,903 5,415 5,915 6,543 6,655 7,255 Class D Bedding Condition 2.5 ft of Cover 5 ft of Cover 4 219 6 297 8 371 10 450 12 507 14 559 16 604 199 270 338 409 461 509 549 498 675 845 1,023 1,153 1,273 1,373 458 634 814 1,012 1,174 1,336 1,484 416 577 740 920 1,068 1,214 1,349 1,040 1,443 1,850 2,300 2,670 3,035 3,373 12 ft of Cover 16 ft of Cover 4 1,127 6 1,584 8 2,051 10 2,451 12 2,678 14 2,886 16 3,130 1,025 1,440 1,864 2,228 2,434 2,623 2,845 2,563 3,600 4,660 5,570 6,085 6 558 7,113 1,510 2,124 2,602 2,835 ; 3,078 3,367 3,663 1,373 1,931 2,366 2,578 2,798 3,061 3,330 3,433 4,828 5,915 6,445 6,995 7,653 8,325 8 ft of Cover 744 1,041 1,344 1,688 1,975 2,267 2,398 677 946 1,221 1,535 1.795 2,061 2,180 1,693 2,365 3,053 3,838 4,488 5,153 5,450 20 ft of Cover 1,893 2,550 2,816 3,076 3,402 3,727 , 4,063 1,721 2,318 2,560 2,796 3,093 3,388 3,693 4,303 5,795 6,400 6,990 7,733 8,470 9,233 CTD000226 20 A-C DISTRIBUTION' PIPE TABLE A2 Design Internal Pressure and Design Earth Load Intercepts for Use With Selection Curves Pipe Size in. 4 6 8 10 12 14 16 Class 100 pw pn lb/lilt ft 417 4,100 441 4,000 472 4,000 490 4,400 490 5,200 500 5,200 500 5,800 Class 150 pw psi Ib/linft 616 5,400 632 5,400 653 5,500 650 7,000 658 7,600 650 8,600 654 9,200 Class 200 p \V psi lb/Untl 809 8,700 815 9,000 824 9,300 826 11,000 830 11,800 826 13,500 825 15,400 A' i\! ; -- ;;a CTD000227