1、Designation: C1786 14Standard Specification forSegmental Precast Reinforced Concrete Box Sections forCulverts, Storm Drains, and Sewers Designed According toAASHTO LRFD1This standard is issued under the fixed designation C1786; the number immediately following the designation indicates the year ofor
2、iginal adoption or, in the case of 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 specification covers precast reinforced concretebox sect
3、ions comprised of separate segments that once prop-erly field assembled make the final structure. These structuresare intended to be used for the construction of culverts and forthe conveyance of storm water, industrial wastes and sewage.NOTE 1This specification is primarily a manufacturing and purc
4、has-ing specification. However, box culverts manufactured to this standard areintended to meet the design requirements of the AASHTO LRFD BridgeDesign Specifications, and as such, design guidance is included inAppendix X1.NOTE 2The successful performance of this product depends upon theproper select
5、ion of the box section, bedding, backfill, and care that theinstallation conforms to the construction specifications. The purchaser ofthe precast reinforced concrete box sections specified herein is cautionedthat proper correlation of the loading conditions and the field requirementswith the box sec
6、tion specified, and provision for inspection at theconstruction site, are required.1.2 The values stated in inch-pound units are to be regardedas standard. No other units of measurement are included in thisstandard.2. Referenced Documents2.1 ASTM Standards:2A615/A615M Specification for Deformed and
7、Plain Carbon-Steel Bars for Concrete ReinforcementA706/A706M Specification for Deformed and Plain Low-Alloy Steel Bars for Concrete ReinforcementA1064/A1064M Specification for Carbon-Steel Wire andWelded Wire Reinforcement, Plain and Deformed, forConcreteC33 Specification for Concrete AggregatesC150
8、 Specification for Portland CementC260 Specification for Air-Entraining Admixtures for Con-creteC309 Specification for Liquid Membrane-Forming Com-pounds for Curing ConcreteC494/C494M Specification for Chemical Admixtures forConcreteC497 Test Methods for Concrete Pipe, Manhole Sections, orTileC595 S
9、pecification for Blended Hydraulic CementsC618 Specification for Coal Fly Ash and Raw or CalcinedNatural Pozzolan for Use in ConcreteC822 Terminology Relating to Concrete Pipe and RelatedProductsC989 Specification for Slag Cement for Use in Concrete andMortarsC1116 Specification for Fiber-Reinforced
10、 Concrete andShotcrete2.2 AASHTO Standards:3AASHTO LRFD Bridge Design SpecificationsAASHTO LRFD Bridge Construction Specifications2.3 ACI Standards:4ACI 318 Building Code Requirements for Structural Con-crete3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 box sectionthe comple
11、ted box culvert unit with allsegments adjoined (see Fig. 1 for configuration options).3.1.2 box segmentthe individual piece (top slab, bottomslab, or three-sided structure) that gets adjoined to other piecesto complete the final box section3.2 DefinitionsFor definitions of terms relating to concrete
12、box culvert sections not found above, see Terminology C822.1This test method is under the jurisdiction of ASTM Committee C13 onConcrete Pipe and is the direct responsibility of Subcommittee C13.07 onAcceptance Specifications and Precast Concrete Box Sections.Current edition approved Nov. 1, 2014. Pu
13、blished December 2014. DOI:10.1520/C178614.2For 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.3Available from Am
14、erican Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.4Available from American Concrete Institute (ACI), P.O. Box 9094, FarmingtonHills, MI 48333-9094, http:/www.concrete.org.Copyright ASTM Inter
15、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1FIG. 1 Segment Configuration OptionsC1786 1424. Basis of Acceptance4.1 Acceptability of the box sections produced in accor-dance with this standard shall be determined by the results ofthe concrete compress
16、ive strength tests described in Section10, by the material requirements described in Section 5, and byinspection of the finished box sections by the owner or theirdesignee.NOTE 3The box culvert structure itself is not complete until it is fullyassembled in the field. Field assembly is not included i
17、n this specification.However, a final field inspection is recommended before the box culvertis considered fit for duty.5. Material5.1 Reinforced ConcreteThe reinforced concrete shallconsist of cementitious materials, mineral aggregates andwater, in which steel has been embedded in such a manner that
18、the steel and concrete act together.5.2 Cementitious Materials:5.2.1 CementCement shall conform to the requirementsfor portland cement of Specification C150 or shall be portlandblast-furnace slag cement or portland-pozzolan cement con-forming to the requirements of Specification C595, except thatthe
19、 pozzolan constituent in the Type IP portland-pozzolancement shall be fly ash.5.2.2 Fly AshFly ash shall conform to the requirements ofSpecification C618, Class F or Class C.5.2.3 Ground Granulated Blast-Furnace SlagGGBFSshall conform to the requirements of Grade 100 or 120 ofSpecification C989.5.2.
20、4 Allowable Combinations of Cementitious MaterialsThe combination of cementitious materials used in concreteshall be one of the following:5.2.4.1 Portland cement only,5.2.4.2 Portland blast furnace slag cement only,5.2.4.3 Portland pozzolan cement only,5.2.4.4 A combination of portland cement and fl
21、y ash,5.2.4.5 A combination of portland cement and groundgranulated blast-furnace slag, or5.2.4.6 A combination of portland cement, ground granu-lated blast-furnace slag (not to exceed 25 % of the totalcementitious weight) and fly ash (not to exceed 25 % of thetotal cementitious weight).5.3 Aggregat
22、esAggregates shall conform to SpecificationC33, except that the requirements for gradation shall not apply.5.4 Admixtures and BlendsThe following admixtures andblends are allowable:5.4.1 Air-entraining admixture conforming to SpecificationC260;5.4.2 Chemical admixture conforming to SpecificationC494
23、/C494M;5.4.3 Chemical admixture or blend approved by the owner.5.5 Steel ReinforcementReinforcement shall consist ofwelded wire reinforcement conforming to SpecificationA1064/A1064M or billet-steel bars conforming to Specifica-tion A615/A615M, Grade 60 or A706/A706M, Grade 60. Thebox culvert segment
24、s shall be manufactured with reinforce-ment meeting the yield strengths designated in the design of thebox culvert, but the yield strength shall not be less than 60 ksi.5.6 Synthetic FibersCollated fibrillated virgin polypropyl-ene fibers may be used at the manufacturers option, inconcrete boxes as
25、a nonstructural manufacturing material. OnlyType III synthetic fibers designed and manufactured specifi-cally for use in concrete and conforming to the requirements ofSpecification C1116 shall be accepted.6. Design6.1 Each segment of the box shall meet the requirements ofthe AASHTO LRFD Bridge Desig
26、n Specifications. Guidanceis given in Appendix X1.6.2 The manufacturer shall maintain on file a copy of asealed “stamped” design by a professional engineer in accor-dance with the AASHTO LRFD Bridge Design Specificationsand this standard for each structure manufactured.6.3 The minimum compressive st
27、rength of concrete seg-ments produced to this standard shall be 4000 psi, unlessotherwise designated by the engineer.6.4 The manufacturer shall produce box culvert segmentsmeeting the design requirements designated in the design of thesegmental precast box structure. As a minimum, the boxculvert seg
28、ments shall meet the reinforcement layout, concretecover, and all other manufacturing details required by thisstandard.6.5 The manufacturer may request approval by the pur-chaser for modified designs which differ from the requirementsin this standard. When such modified designs are approved, itshall
29、 be so indicated on the manufactured box with thedesignation “C1786Modified.”NOTE 4(Advisory)Construction procedures, such as heavy equip-ment movement or stockpiling of material over or adjacent to a boxstructure can induce higher loads than those used for the structures finaldesign. These construc
30、tion and surcharge loads are allowable as long asthe final steel areas in the box are equal to or larger than those required forthe construction phase. The design engineer shall take into considerationthe potential for higher loads induced by construction procedures indetermining the final design of
31、 the box structure.7. Reinforcement7.1 Placement of ReinforcementReinforcement shall beassembled utilizing any combination of single or multiplelayers of welded wire reinforcement, not to exceed three layers,or utilizing single or double layers of deformed billet steel bars.The cover of concrete ove
32、r the circumferential reinforcementshall be 1 in. except for when the box culvert has less than 2 ftof earth cover, then the concrete cover over the top slabreinforcement shall be 2 inches (see Figs. 2 and 3). Concretecover shall be subject to the provisions of Section 11. Thewelded wire reinforceme
33、nt shall be composed of circumferen-tial and longitudinal wires meeting the spacing requirements of7.2 and shall contain sufficient longitudinal wires extendingthrough the box section to maintain the shape and position ofreinforcement. Longitudinal distribution reinforcement shall bewelded-wire rein
34、forcement or deformed billet-steel bars andshall meet the spacing requirements of 7.2. The ends of thelongitudinal distribution reinforcement shall not be more thanC1786 1432 in. from the ends of the box section. The exposure of the endsof longitudinals, stirrups, and spacers used to position therei
35、nforcement shall not be a cause for rejection.7.2 Laps, Welds, and SpacingWhen deformed billet steelbars are utilized for the primary reinforcing, the requirementsin the AASHTO LRFD Bridge Design Specifications, Section5.11 for splices and development of reinforcement shall befollowed. When wire rei
36、nforcement is utilized, the require-ments of this section shall be followed. Splices in the circum-ferential reinforcement shall be made by lapping. The overlapmeasured between the outermost longitudinal wires of eachreinforcement sheet shall not be less than the space containingtwo longitudinal wir
37、es of each mesh plus 2 in., but not less than10 inches. No splicing is permitted in individual slab segments.The outside circumferential reinforcement in the top or bottomslab of a three-sided segment shall be continuous with, orlapped with the outside circumferential reinforcement in thesides. If w
38、elds are made to welded wire circumferentialreinforcement, they shall be made only to selected circumfer-ential wires that are not less than 18 in. apart along thelongitudinal axis of the three-sided section. When spacers arewelded to circumferential wires, they shall be welded only tothese selected
39、 circumferential wires. There shall be no weldingto other circumferential wires. No welds shall be made to theinside circumferential wires in the middle third of the top span.No welds shall be made to the outside circumferential wires inFIG. 2 Top Slab Reinforcement Placement(Joint configuration is
40、for illustration purposes only, and other configurations are acceptable.)FIG. 3 Bottom Slab Reinforcement Placement(Joint configuration is for illustration purposes only, and other configurations are acceptable.)C1786 144the top span within one fourth of the span from the corners orin any location i
41、n either leg. Welding of deformed billet steelbar circumferential reinforcement is prohibited in all cases.When distribution reinforcement is fastened to a cage bywelding, it shall be welded only to longitudinal wires or barsand only near the ends of the three-sided section. The spacingcenter to cen
42、ter of the circumferential reinforcement shall notbe less than 2 in. nor more than 4 in. for welded wirereinforcement, or less than 2 in. nor more than 8 in. fordeformed billet steel bars. The spacing center to center of thelongitudinal reinforcement shall not be more than 8 in. forwelded wire reinf
43、orcement or more than 12 in. for deformedbillet steel bars. If welds are made to Grade 60 reinforcing bars,weldable bars conforming to Specification A706/A706M shallbe used.NOTE 5(Advisory)The AASHTO LRFD Bridge Design Specifica-tions should be consulted for weld requirements and development lengths
44、not directly addressed in this standard.7.3 Minimum ReinforcementBox culvert sections withless than 2 ft of earth or pavement cover shall containdistribution reinforcement in the bottom of the top slab inaccordance with Article 9.7.3.2 of the AASHTO LRFD BridgeDesign Specifications, but shall be no
45、less than 0.02*Ag inaccordance with Article 12.11.4.3.7.4 Substitution of ReinforcingDeformed billet steel barscannot be substituted as a replacement for steel areas based ona welded wire reinforcement design without approval by theengineer.NOTE 6Because of the difference in yield stress between bar
46、s andwire, and the differences in spacing required for larger and smallerdiameter reinforcement, the steel area for deformed bars may have to beincreased to account for flexure and/or crack control.8. Joints8.1 The ends of the box segments shall be of such designthat each segment can be fitted toget
47、her to form a complete boxsection unit. The ends of the box section units shall be soformed that the sections can be laid together to make acontinuous line of box sections compatible with the permis-sible variations given in Section 11.8.2 Longitudinal joints shall be designed to carry the ap-plied
48、vertical forces, and so formed so that they can beassembled to transmit forces and provide joint tightnessconsistent with the requirements for transverse joints.9. Manufacture9.1 MixtureThe aggregates shall be sized, graded,proportioned, and mixed with such proportions of cementitiousmaterials and w
49、ater as will produce a thoroughly mixedconcrete of such quality that the box section will conform tothe test and design requirements of this specification. Allconcrete shall have a water-cementitious materials ratio notexceeding 0.50 by weight. Cementitious materials shall be asspecified in 5.2 and shall be added to the mix in a proportionnot less than 470 lb/yd3unless mix designs with a lowercementitious materials content demonstrate that the quality andperformance of the box section meet the requirements of thisspecification.9.2 CuringThe box segm
