1、Designation: C857 14Standard 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 revision,
2、 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 deadloads to be applied when designing monolithic or s
3、ectionalprecast concrete utility structures. Concrete pipe, box culverts,and material covered in Specification C478 are excluded fromthis practice.NOTE 1For additional information see AASHTO Standard Specifica-tion for Highway Bridges, Seventeenth Edition.NOTE 2The purchaser is cautioned that he mus
4、t properly correlate theanticipated loading conditions and the field requirements with the designloads used.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are n
5、ot considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior
6、 to use.2. Referenced Documents2.1 ASTM Standards:2C478 Specification for Precast Reinforced Concrete Man-hole 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 of any other
7、 load that canaffect the design of the structure.3.1.2 lifting insertdevice embedded or otherwise attachedto the structure, designed and manufactured to support ameasured, sustained, concentrated load.3.1.3 live loadswill consist of any moving loads that canaffect the design of the structure and the
8、ir associated impactand surcharge 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 ator below ground level consists of the live loads includingimpact and dead loads that c
9、an develop as a result of earthpressure, hydrostatic pressure, and construction materials suchas used for roadways and walkways.4.1.1 Live LoadsThe vehicle and pedestrian load designa-tions are given in Table 1. Live load wheel spacing is shown inFig. 1.4.1.2 Impact:4.1.2.1 The live loads A-16, A-12
10、, and A-8 shall be in-creased as follows to sustain the effect of impact:4.1.2.2 Live Load Increase:0 to 12 in. (0 to 305 mm) 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,
11、0 %4.1.3 Dead LoadsDead loads will consist of the weight ofthe roof, roadbed, walkways, earth fill, access opening covers,and any other material that produces a static load.4.1.3.1 Recommended unit weights of materials for designcalculations are as follows:Concrete, plain, and reinforced 150 lb/ft3(
12、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) 110 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 consideredapplied to a wheel l
13、oad area as indicated in Fig. 2.1This practice is under the jurisdiction of ASTM Committee C27 on PrecastConcrete Products and is the direct responsibility of Subcommittee C27.10 onUtility Structures.Current edition approved March 1, 2014. Published March 2014. Originallyapproved in 1978. Last previ
14、ous edition approved in 2013 as C857 13. DOI:10.1520/C0857-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website
15、.3Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.1.4.2
16、Wheel loads shall be distributed below ground levelas a truncated pyramid, as shown in Fig. 3, in which the topsurface is the wheel load area and the distributed load area isequal to the following:DLA 5 W11.75 H!L11.75 H! (1)where:DLA = distributed load area, ft2(m2)W = wheel load width, ft (m),L =
17、wheel load length, ft (m), andH = depth of fill, ft (m).4.1.4.3 When several distributed load areas overlap, thetotal load shall be considered as uniformly distributed over thearea defined by the outside limits of the individual areas asindicated in Fig. 4. When the dimensions of the com-positedistr
18、ibuted load area exceeds the roof area only that portion ofthe distributed load on the roof area shall be considered in thedesign.4.1.4.4 The distribution of wheel loads through earth fill areneglected when the depth of fill exceeds 8 ft (2.5 m).4.2 WallsThe design loads for the walls of any structu
19、re ator below ground level will consist of surcharge loads resultingfrom live loads, lateral earth loads that can develop as a resultof earth pressure, hydrostatic pressure, and construction mate-rials such as used for roadways and walkways. Load diagramsof live load surcharge and lateral earth load
20、s are shown in Fig.5.4.2.1 Live Loads:4.2.1.1 When traffic can come within a horizontal distancefrom the structure equal to one half the height of the structure,a live load surcharge pressure of not less than 0.5 % of thewheel loading of the traffic involved shall be taken as the liveload acting upo
21、n the wall of the structure.4.2.1.2 Surcharge pressures for various live loads trans-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 0.0
22、05 = 40 lbf/ft2(1915 Pa) per wheelA-0.3 Refer to 4.2.2.14.2.1.3 Surcharge pressures resulting from live loads areneglected when the distance from ground level exceeds 8 ft(2.5 m).4.2.2 Lateral Earth Loads:4.2.2.1 The lateral earth loads will consist of an earthpressure above ground water level and h
23、ydrostatic pressureplus a modified earth pressure below ground water level. Theearth pressure above ground water level and the modified earthpressure below ground water level will be converted to ahorizontal pressure using Rankines Theory on active earthpressure. No structure will be designed for le
24、ss than a 30 lb/ft2(1436 Pa) horizontal pressure.4.2.2.2 For the general case when structures are placed inareas where the soil surface does not slope the horizontalpressure acting at a point on the wall of the structure aboveground water level will be:P 5 Ka3W 3H (2)where:P = horizontal pressure, l
25、bf/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 wallunder consideration, ft (m).4.2.2.3 In special cases, when structures are place
26、d in areaswhere the soil surface is sloping, the horizontal pressure actingat a point on the structure above ground water level is asfollows:P 5 cos KaWsH (3)where:P = horizontal pressure, lbf/ft2(Pa),Ka= coefficient of active earth pressure =cos cos 2 = cos2 2 cos2cos 1= cos2 2 cos2(4) = angle of i
27、nternal friction of the soil, deg (rad), = angle between the sloping soil surface and thehorizontal, deg (rad)Ws= unit weight of soil, lb/ft3(kg/m3), andH = distance from ground level to the point on the wallunder consideration, ft (m).The horizontal pressure below ground water level resultingfrom t
28、he weight of soil above ground water level is equal to thehorizontal pressure at ground water level and will remainconstant from ground water level to the base of structure.4.2.2.4 The horizontal pressure that can develop belowground water level will consist of a full hydrostatic pressureplus horizo
29、ntal pressure resulting from the weight of sub-merged soil. The hydrostatic pressure acting at a point on thewall of the structure below ground water level is:Pw5 WwHw(5)where:Pw= hydrostatic pressure, lbf/ft2(Pa),Ww= unit weight of water, lb/ft3(kg/m3), andHw= distance from ground water level to th
30、e point on thewall under consideration, ft (m).The horizontal pressure acting at a point on the wall of thestructure below ground water level resulting from the weight ofsubmerged soil is:TABLE 1 Vehicle and Pedestrian Load DesignationsDesignations Maximum Loads UsesA-16 (HS20-44)A16 000 lbf (71 172
31、 N)/wheel heavy trafficA-12 (HS15-44)A12 000 lbf (53 376 N)/wheel medium trafficA-8 (H10-44)A8 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
32、designated by purchaser.C857 142FIG. 1 Live Load SpacingC857 143Ps5 Ws2 Ww! KaHw(6)where:P = horizontal pressure from submerged soil, lbf/ft2(Pa)WsWw= 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 internal fr
33、iction of the soil, deg (rad),andHw= distance from ground water level to the point onthe wall under consideration, ft (m).NOTE 3The coefficient of active earth pressure is used for the generalcase where the soil surface does not slope.4.3 Base:4.3.1 Live LoadsThe live loads transmitted to the baseco
34、nsist of the maximum value possible of live loads that can beimposed on the roof. This includes the total number of wheelloads that can simultaneously be placed on the structure.4.3.2 Dead LoadsThe dead loads on the base consist ofthe dead loads imposed on the roof plus the weight of thestructure ex
35、cluding the base, or the hydrostatic pressure actingon the base, whichever is greater.4.4 Accessories Loading:FIG. 2 Wheel Load AreaFIG. 3 Distributed Load AreaC857 1444.4.1 Cable Pulling DevicesCable pulling devices in allstructures are designed for the working loads specified by thespecific user.
36、These working loads can be compensated for inthe design of the structure and are considered in addition to thedesign loads.4.4.2 Lifting InsertsLifting inserts in all structures aredesigned for a load equivalent to four times the maximum loadtransmitted to the insert. The loads imposed at the liftin
37、g pointsare considered in the design of the structure.4.4.3 Equipment Mounting DevicesThe structure is de-signed to accommodate loads induced by the equipmentinstalled on the mounting device, as required by the user. Theseloads are considered in the design of the structure.4.5 Buoyancy EffectsThe st
38、ructural design for belowground structures will also consider buoyancy effects, ifapplicable, and proportion the structure to ensure an adequatesafety factor.5. Significance and Use5.1 This practice is intended to standardize the minimumstructural design loading for underground precast concreteutili
39、ty structures.5.2 The user shall verify the anticipated field conditions andrequirements with design loads greater than those specified inthis standard.6. Keywords6.1 minimum structural design criteria; precast concrete;underground utility enclosuresFIG. 4 Overlapping Load AreasC857 145ASTM Internat
40、ional 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 infringement of such rights, are entirely the
41、ir 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 for additional standardsand should
42、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 known to the ASTM Committee on Standar
43、ds, 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/).FIG. 5 Load Diagrams of Live Load Surcharge and Lateral Earth LoadsC857 146
