1、Designation: C1786 14C1786 16Standard 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 y
2、ear oforiginal 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 concrete
3、 box sections comprised of separate segments that once properly fieldassembled make the final structure. These structures are intended to be used for the construction of culverts and for the conveyanceof storm water, industrial wastes and sewage.NOTE 1This specification is primarily a manufacturing
4、and purchasing specification. However, box culverts manufactured to this standard areintended to meet the design requirements of the AASHTO LRFD Bridge Design Specifications, and as such, design guidance is included in AppendixX1.NOTE 2The successful performance of this product depends upon the prop
5、er selection of the box section, bedding, backfill, and care that theinstallation conforms to the construction specifications. The purchaser of the precast reinforced concrete box sections specified herein is cautioned thatproper correlation of the loading conditions and the field requirements with
6、the box section specified, and provision for inspection at the construction site,are required.1.2 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in thisstandard.2. Referenced Documents2.1 ASTM Standards:2A615/A615M Specification for D
7、eformed and 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 and Welded Wire Reinforcement, Plain and Deformed, for ConcreteC33 Specification for Concrete
8、AggregatesC150 Specification for Portland CementC260 Specification for Air-Entraining Admixtures for ConcreteC309 Specification for Liquid Membrane-Forming Compounds for Curing ConcreteC494/C494M Specification for Chemical Admixtures for ConcreteC497 Test Methods for Concrete Pipe, Manhole Sections,
9、 or TileC595 Specification for Blended Hydraulic CementsC618 Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in ConcreteC822 Terminology Relating to Concrete Pipe and Related ProductsC989 Specification for Slag Cement for Use in Concrete and MortarsC1116 Specification for
10、 Fiber-Reinforced Concrete and Shotcrete2.2 AASHTO Standards:3AASHTO LRFD Bridge Design SpecificationsAASHTO LRFD Bridge Construction Specifications1 This test method is under the jurisdiction of ASTM Committee C13 on Concrete Pipe and is the direct responsibility of Subcommittee C13.07 on Acceptanc
11、eSpecifications and Precast Concrete Box Sections.Current edition approved Nov. 1, 2014Feb. 1, 2016. Published December 2014February 2016. Originally approved in 2014. Las previous edition approved in 2014 asC1786 14. DOI: 10.1520/C178614.10.1520/C178616.2 For referencedASTM standards, visit theASTM
12、 website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American Association of State Highway and Transportation Officials (AASHTO), 444 N. Capit
13、ol 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 indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately de
14、pict 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 considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
15、9428-2959. United States12.3 ACI Standards:4ACI 318 Building Code Requirements for Structural Concrete3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 box sectionthe completed box culvert unit with all segments adjoined (see Fig. 1 for configuration options).3.1.2 box segmentth
16、e individual piece (top slab, bottom slab, or three-sided structure) that gets adjoined to other pieces tocomplete the final box section3.2 DefinitionsFor definitions of terms relating to concrete box culvert sections not found above, see Terminology C822.4. Basis of Acceptance4.1 Acceptability of t
17、he box sections produced in accordance with this standard shall be determined by the results of theconcrete compressive strength tests described in Section 10, by the material requirements described in Section 5, and by inspectionof the finished box sections by the owner or their designee.NOTE 3The
18、box culvert structure itself is not complete until it is fully assembled in the field. Field assembly is not included in this specification.However, a final field inspection is recommended before the box culvert is considered fit for duty.5. Material5.1 Reinforced ConcreteThe reinforced concrete sha
19、ll consist of cementitious materials, mineral aggregates and water, inwhich steel has been embedded in such a manner that the steel and concrete act together.5.2 Cementitious Materials:5.2.1 CementCement shall conform to the requirements for portland cement of Specification C150 or shall be portland
20、blast-furnace slag cement or portland-pozzolan cement conforming to the requirements of Specification C595, except that thepozzolan constituent in the Type IP portland-pozzolan cement shall be fly ash.5.2.2 Fly AshFly ash shall conform to the requirements of Specification C618, Class F or Class C.5.
21、2.3 Ground Granulated Blast-Furnace SlagGGBFS shall conform to the requirements of Grade 100 or 120 of SpecificationC989.5.2.4 Allowable Combinations of Cementitious MaterialsThe combination of cementitious materials used in concrete shall beone of the following:5.2.4.1 Portland cement only,5.2.4.2
22、Portland blast furnace slag cement only,5.2.4.3 Portland pozzolan cement only,5.2.4.4 A combination of portland cement and fly ash,5.2.4.5 A combination of portland cement and ground granulated blast-furnace slag, or5.2.4.6 A combination of portland cement, ground granulated blast-furnace slag (not
23、to exceed 25 % of the total cementitiousweight) and fly ash (not to exceed 25 % of the total cementitious weight).5.3 AggregatesAggregates shall conform to Specification C33, except that the requirements for gradation shall not apply.5.4 Admixtures and BlendsThe following admixtures and blends are a
24、llowable:5.4.1 Air-entraining admixture conforming to Specification C260;5.4.2 Chemical admixture conforming to Specification C494/C494M;5.4.3 Chemical admixture or blend approved by the owner.5.5 Steel ReinforcementReinforcement shall consist of welded wire reinforcement conforming to Specification
25、 A1064/A1064M or billet-steel bars conforming to Specification A615/A615M, Grade 60 or A706/A706M, Grade 60. The box culvertsegments shall be manufactured with reinforcement meeting the yield strengths designated in the design of the box culvert, butthe yield strength shall not be less than 60 ksi.5
26、.6 Synthetic FibersCollated fibrillated virgin polypropylene fibers may be used at the manufacturers option, in concreteboxes as a nonstructural manufacturing material. Only Type III synthetic fibers designed and manufactured specifically for use inconcrete and conforming to the requirements of Spec
27、ification C1116 shall be accepted.6. Design6.1 Each segment of the box shall meet the requirements of the AASHTO LRFD Bridge Design Specifications. Guidance isgiven in Appendix X1.4 Available from American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094, http:/www.concrete.o
28、rg.C1786 162FIG. 1 Segment Configuration OptionsC1786 1636.2 The manufacturer shall maintain on file a copy of a sealed “stamped” design by a professional engineer in accordance withthe AASHTO LRFD Bridge Design Specifications and this standard for each structure manufactured.6.3 The minimum compres
29、sive strength of concrete segments produced to this standard shall be 4000 psi, unless otherwisedesignated by the engineer.6.4 The manufacturer shall produce box culvert segments meeting the design requirements designated in the design of thesegmental precast box structure.As a minimum, the box culv
30、ert segments shall meet the reinforcement layout, concrete cover, andall other manufacturing details required by this standard.6.5 The manufacturer may request approval by the purchaser for modified designs which differ from the requirements in thisstandard. When such modified designs are approved,
31、it shall be so indicated on the manufactured box with the designation“C1786Modified.”NOTE 4(Advisory)Construction procedures, such as heavy equipment movement or stockpiling of material over or adjacent to a box structure caninduce higher loads than those used for the structures final design. These
32、construction and surcharge loads are allowable as long as the final steel areasin the box are equal to or larger than those required for the construction phase. The design engineer shall take into consideration the potential for higherloads induced by construction procedures in determining the final
33、 design of the box structure.7. Reinforcement7.1 Placement of ReinforcementReinforcement shall be assembled utilizing any combination of single or multiple layers ofwelded wire reinforcement, not to exceed three layers, or utilizing single or double layers of deformed billet steel bars. The coverof
34、concrete over the circumferential reinforcement shall be 1 in. except for when the box culvert has less than 2 ft of earth cover,then the concrete cover over the top slab reinforcement shall be 2 inches (see Figs. 2 and 3). Concrete cover shall be subject tothe provisions of Section 11. The welded w
35、ire reinforcement shall be composed of circumferential and longitudinal wires meetingthe spacing requirements of 7.2 and shall contain sufficient longitudinal wires extending through the box section to maintain theshape and position of reinforcement. Longitudinal distribution reinforcement shall be
36、welded-wire reinforcement or deformedbillet-steel bars and shall meet the spacing requirements of 7.2. The ends of the longitudinal distribution reinforcement shall notbe more than 2 in. from the ends of the box section. The exposure of the ends of longitudinals, stirrups, and spacers used to positi
37、onthe reinforcement shall not be a cause for rejection.7.2 Laps, Welds, and SpacingWhen deformed billet steel bars are utilized for the primary reinforcing, the requirements in theAASHTO LRFD Bridge Design Specifications, Section 5.11 for splices and development of reinforcement shall be followed.Wh
38、enwire reinforcement is utilized, the requirements of this section shall be followed. Splices in the circumferential reinforcement shallbe made by lapping. The overlap measured between the outermost longitudinal wires of each reinforcement sheet shall not be lessthan the space containing two longitu
39、dinal wires of each mesh plus 2 in., but not less than 10 inches. No splicing is permitted inindividual slab segments. The outside circumferential reinforcement in the top or bottom slab of a three-sided segment shall becontinuous with, or lapped with the outside circumferential reinforcement in the
40、 sides. If welds are made to welded wireFIG. 2 Top Slab Reinforcement Placement(Joint configuration is for illustration purposes only, and other configurations are acceptable.)C1786 164circumferential reinforcement, they shall be made only to selected circumferential wires that are not less than 18
41、in. apart alongthe longitudinal axis of the three-sided section. When spacers are welded to circumferential wires, they shall be welded only tothese selected circumferential wires. There shall be no welding to other circumferential wires. No welds shall be made to the insidecircumferential wires in
42、the middle third of the top span. No welds shall be made to the outside circumferential wires in the topspan within one fourth of the span from the corners or in any location in either leg. Welding of deformed billet steel barcircumferential reinforcement is prohibited in all cases. When distributio
43、n reinforcement is fastened to a cage by welding, it shallbe welded only to longitudinal wires or bars and only near the ends of the three-sided section. The spacing center to center of thecircumferential reinforcement shall not be less than 2 in. nor more than 4 in. for welded wire reinforcement, o
44、r less than 2 in. normore than 8 in. for deformed billet steel bars. The spacing center to center of the longitudinal reinforcement shall not be more than8 in. for welded wire reinforcement or more than 12 in. for deformed billet steel bars. If welds are made to Grade 60 reinforcingbars, weldable ba
45、rs conforming to Specification A706/A706M shall be used.NOTE 5(Advisory)The AASHTO LRFD Bridge Design Specifications should be consulted for weld requirements and development lengths notdirectly addressed in this standard.7.3 Minimum ReinforcementBox culvert sections with less than 2 ft of earth or
46、pavement cover shall contain distributionreinforcement in the bottom of the top slab in accordance withArticle 9.7.3.2 of theAASHTO LRFD Bridge Design Specifications,but shall be no less than 0.02*Ag in accordance with Article 12.11.4.3.7.4 Substitution of ReinforcingDeformed billet steel bars canno
47、t be substituted as a replacement for steel areas based on awelded wire reinforcement design without approval by the engineer.NOTE 6Because of the difference in yield stress between bars and wire, and the differences in spacing required for larger and smaller diameterreinforcement, the steel area fo
48、r deformed bars may have to be increased to account for flexure and/or crack control.8. Joints8.1 The ends of the box segments shall be of such design that each segment can be fitted together to form a complete box sectionunit. The ends of the box section units shall be so formed that the sections c
49、an be laid together to make a continuous line of boxsections compatible with the permissible variations given in Section 11.8.2 Longitudinal joints shall be designed to carry the applied vertical forces, and so formed so that they can be assembled totransmit forces and provide joint tightness consistent with the requirements for transverse joints.9. Manufacture9.1 MixtureThe aggregates shall be sized, graded, proportioned, and mixed with such proportions of cementitious materialsand water as will produce a thoroughly mixed concrete of such quali
