1、Designation: C857 12a C857 13Standard Practice forMinimum Structural Design Loading for UndergroundPrecast Concrete Utility Structures1This standard is issued under the fixed designation C857; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes the minimum live loads and dead loads to be applied when designing monol
3、ithic or sectional precastconcrete utility structures. Concrete pipe, box culverts, and material covered in Specification C478 are excluded from this practice.NOTE 1For additional information see AASHTO Standard Specification for Highway Bridges, Seventeenth Edition.NOTE 2The purchaser is cautioned
4、that he must properly correlate the anticipated loading conditions and the field requirements with the design loadsused.1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information
5、only and are not considered standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimit
6、ations prior to use.2. Referenced Documents2.1 ASTM Standards:2C478 Specification for Precast Reinforced Concrete Manhole Sections2.2 AASHTO Standard:Specification for Highway Bridges, Seventeenth Edition33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 dead loadswill consist o
7、f any other load that can affect the design of the structure.3.1.2 lifting insertdevice embedded or otherwise attached to the structure, designed and manufactured to support a measured,sustained, concentrated load.3.1.3 live loadswill consist of any moving loads that can affect the design of the str
8、ucture and their associated impact andsurcharge loads.3.1.4 utility structurea structure that is used by electric, gas, communication, or similar industries.4. Design Loads4.1 RoofThe design loads for the roof of any structure at or below ground level consists of the live loads including impactand d
9、ead loads that can develop as a result of earth pressure, hydrostatic pressure, and construction materials such as used forroadways and walkways.4.1.1 Live LoadsThe vehicle and pedestrian load designations are given in Table 1. Live load wheel spacing is shown in Fig.1.4.1.2 Impact:1 This practice i
10、s under the jurisdiction of ASTM Committee C27 on Precast Concrete Products and is the direct responsibility of Subcommittee C27.10 on UtilityStructures.Current edition approved Jan. 15, 2012Jan. 1, 2013. Published January 2012January 2013. Originally approved in 1978. Last previous edition approved
11、 in 2012 asC857 12.C857 12a. DOI: 10.1520/C0857-12A.10.1520/C0857-13.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the AS
12、TM website.3 Available from American Association of State Highway and Transportation Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indicati
13、on of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be consi
14、dered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.1.2.1 The live loads A-16, A-12, and A-8 shall be increased as follows to sustain the effect of impact:4.1.2.2 Live Load Increase:0 to 12 in. (0 to 305 mm)
15、below ground level, 30 %13 to 24 in. (330 to 610 mm) below ground level, 20 %25 to 35 in. (635 to 889 mm) below ground level, 10 %36 in. (914 mm) or more below ground level, 0 %4.1.3 Dead LoadsDead loads will consist of the weight of the roof, roadbed, walkways, earth fill, access opening covers, an
16、dany other material that produces a static load.4.1.3.1 Recommended unit weights of materials for design calculations are as follows:Concrete, plain, and reinforced 150 lb/ft3 (2043 kg/m3)Cast iron 450 lb/ft3 (7208 kg/m3)Steel 490 lb/ft3 (7850 kg/m3)Aluminum 175 lb/ft3 (2804 kg/m3)Earth fill (dry) 1
17、10 lb/ft3 (1762 kg/m3)Macadam 140 lb/ft3 (2243 kg/m3)4.1.4 Distribution of Wheel Loads Through Earth Fills:4.1.4.1 Wheel loads at ground level shall be considered applied to a wheel load area as indicated in Fig. 2.4.1.4.2 Wheel loads shall be distributed below ground level as a truncated pyramid, a
18、s shown in Fig. 3, in which the top surfaceis the wheel load area and the distributed load area is equal to the following:DLA5W11.75 H! L11.75 H! (1)where:DLA = distributed load area, ft2(m2)W = wheel load width, ft (m),L = wheel load length, ft (m), andH = depth of fill, ft (m).4.1.4.3 When several
19、 distributed load areas overlap, the total load shall be considered as uniformly distributed over the areadefined by the outside limits of the individual areas as indicated in Fig. 4. When the dimensions of the com-posite distributed loadarea exceeds the roof area only that portion of the distribute
20、d load on the roof area shall be considered in the design.4.1.4.4 The distribution of wheel loads through earth fill are neglected when the depth of fill exceeds 8 ft (2.5 m).4.2 WallsThe design loads for the walls of any structure at or below ground level will consist of surcharge loads resulting f
21、romlive loads, dead loads that can develop as a result of earth pressure, hydrostatic pressure, and construc-tion materials such as usedfor roadways and walkways. Load diagrams of live load surcharge and dead loads are shown in Fig. 5.4.2.1 Live Loads:4.2.1.1 When traffic can come within a horizonta
22、l distance from the structure equal to one half the height of the structure, a liveload surcharge pressure of not less than 0.5 % of the wheel loading of the traffic involved shall be taken as the live load actingupon the wall of the structure.4.2.1.2 Surcharge pressures for various live loads trans
23、ferred to equivalent horizontal fluid pressure are as follows:A-16 16 000 lbf per wheel 0.005 = 80 lbf/ft2 (3830 Pa) per wheelA-12 12 000 lbf per wheel 0.005 = 60 lbf/ft2 (2873 Pa) per wheelA-8 8 000 lbf per wheel 0.005 = 40 lbf/ft2 (1915 Pa) per wheelA-0.3 Refer to 4.2.2.14.2.1.3 Surcharge pressure
24、s resulting from live loads are neglected when the distance from ground level exceeds 8 ft (2.5 m).4.2.2 Dead Loads:4.2.2.1 The dead loads will consist of an earth pressure above ground water level and hydrostatic pressure plus a modified earthpressure below ground water level. The earth pressure ab
25、ove ground water level and the modified earth pressure below groundwater level will be converted to a horizontal pressure using Rankines Theory on active earth pressure. No structure will bedesigned for less than a 30 lb/ft2 (1436 Pa) horizontal pressure.4.2.2.2 For the general case when structures
26、are placed in areas where the soil surface does not slope the horizontal pressureacting at a point on the wall of the structure above ground water level will be:TABLE 1 Vehicle and Pedestrian Load DesignationsDesignations Maximum Loads UsesA-16 (HS20-44)A 16 000 lbf (71 172 N)/wheel heavy trafficA-1
27、2 (HS15-44)A 12 000 lbf (53 376 N)/wheel medium trafficA-8 (H10-44)A 8 000 lbf (35 586 N)/wheel light trafficA-0.3 300 lbf/ft2 (14.4 kPa) walkwaysBAThe designations in parentheses are the corresponding AASHTO designations.BAnticipated designs other than those listed should be designated by purchaser
28、.C857 132P 5Ka 3W 3H (2)where:P = horizontal pressure, lbf/ft2 (Pa)Ka = coefficient of active earth pressure = (1 sin )/(1 + sin ) = angle of internal friction of the soil, deg (rad),W = unit weight of soil, lb/ft3 (kg/m3) andH = distance from ground level to the point on the wall under consideratio
29、n, ft (m).4.2.2.3 In special cases, when structures are placed in areas where the soil surface is sloping, the horizontal pressure acting ata point on the structure above ground water level is as follows:P 5 cos Ka Ws H (3)FIG. 1 Live Load SpacingC857 133where:P = horizontal pressure, lbf/ft2 (Pa),K
30、a = coefficient of active earth pressure =cos cos 2= cos2 2 cos 2 cos 1= cos 2 2 cos 2(4) = angle of internal friction of the soil, deg (rad), = angle between the sloping soil surface and the horizontal, deg (rad)Ws = unit weight of soil, lb/ft3 (kg/m 3), andH = distance from ground level to the poi
31、nt on the wall under consideration, ft (m).The horizontal pressure below ground water level resulting from the weight of soil above ground water level is equal to thehorizontal pressure at ground water level and will remain constant from ground water level to the base of structure.FIG. 2 Wheel Load
32、AreaFIG. 3 Distributed Load AreaC857 1344.2.2.4 The horizontal pressure that can develop below ground water level will consist of a full hydrostatic pressure plushorizontal pressure resulting from the weight of submerged soil. The hydrostatic pressure acting at a point on the wall of thestructure be
33、low ground water level is:Pw 5Ww Hw (5)where:Pw = hydrostatic pressure, lbf/ft2 (Pa),Ww = unit weight of water, lb/ft3 (kg/m3), andHw = distance from ground water level to the point on the wall under consideration, ft (m).The horizontal pressure acting at a point on the wall of the structure below g
34、round water level resulting from the weight ofsubmerged soil is:Ps 5Ws 2Ww! Ka Hw (6)where:P = horizontal pressure from submerged soil, lbf/ft2 (Pa)Ws Ww = unit weight of soil less the unit weight of water, lb/ft3 (kg/m3),Ka = coefficient of active earth pressure = (1 sin )/(1 + sin ), = angle of in
35、ternal friction of the soil, deg (rad), andHw = distance from ground water level to the point on the wall under consideration, ft (m).NOTE 3The coefficient of active earth pressure is used for the general case where the soil surface does not slope.4.3 Base:4.3.1 Live LoadsThe live loads transmitted
36、to the base consist of the maximum value possible of live loads that can beimposed on the roof. This includes the total number of wheel loads that can simultaneously be placed on the structure.4.3.2 Dead LoadsThe dead loads on the base consist of the dead loads imposed on the roof plus the weight of
37、 the structureexcluding the base, or the hydrostatic pressure acting on the base, whichever is greater.4.4 Accessories Loading:4.4.1 Cable Pulling DevicesCable pulling devices in all structures are designed for the working loads specified by the specificuser. These working loads can be compensated f
38、or in the design of the structure and are considered in addition to the design loads.4.4.2 Lifting InsertsLifting inserts in all structures are designed for a load equivalent to four times the maximum loadtransmitted to the insert. The loads imposed at the lifting points are considered in the design
39、 of the structure.4.4.3 Equipment Mounting DevicesThe structure is designed to accommodate loads induced by the equipment installed on themounting device, as required by the user. These loads are considered in the design of the structure.4.5 Buoyancy EffectsThe structural design for below ground str
40、uctures will also consider buoyancy effects, if applicable, andproportion the structure to ensure an adequate safety factor.5. Significance and Use5.1 This practice is intended to standardize the minimum structural design loading for underground precast concrete utilitystructures.5.2 The user shall
41、verify the anticipated field conditions and requirements with design loads greater than those specified in thisstandard.FIG. 4 Overlapping Load AreasC857 135FIG. 5 Load Diagrams of Live Load Surcharge and Dead LoadsC857 1366. Keywords6.1 minimum structural design criteria; precast concrete; undergro
42、und utility enclosuresASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringeme
43、nt of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or
44、for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views kno
45、wn to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).C857 137
