1、ACI 408.3R-09Reported by Joint ACI-ASCE Committee 408Guide for Lap Splice and DevelopmentLength of High Relative Rib AreaReinforcing Bars in Tensionand CommentaryGuide for Lap Splice and Development Length of High Relative Rib AreaReinforcing Bars in Tension and CommentaryFirst PrintingOctober 2009I
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10、oad, on CD-ROM, through electronicsubscription, or reprint and may be obtained by contacting ACI.Most ACI standards and committee reports are gathered together in the annually revised ACI Manual ofConcrete Practice (MCP).American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.
11、S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgACI 408.3R-09 supersedes ACI 408.3-01 and was adopted and published October 2009.Copyright 2009, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies
12、 by any photo process, or by electronic ormechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.408.3R-1ACI Committee Reports, Guid
13、es, Manuals, and Commentariesare intended for guidance in planning, designing, executing,and inspecting construction. This document is intended for theuse of individuals who are competent to evaluate thesignificance and limitations of its content and recommendationsand who will accept responsibility
14、 for the application of thematerial it contains. The American Concrete Institute disclaimsany and all responsibility for the stated principles. The Instituteshall not be liable for any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found
15、in this document are desired by theArchitect/Engineer to be a part of the contract documents, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.Guide for Lap Splice and Development Length of High Relative Rib Area Reinforcing Bars in Tensionand CommentaryReported
16、 by Joint ACI-ASCE Committee 408ACI 408.3R-09This guide provides recommended requirements to determine tensiondevelopment and splice lengths for high relative rib area bar reinforce-ment, which are not in commercial production in the U.S. at the time ofpublication. When such requirements are applica
17、ble for a project, the usermay incorporate the information in this guide into a legal document;however, this guide is not an ACI standard and shall not be adopted byreference into legal documents.To assist the user to incorporate the information into a legal document,the relevant portion of the docu
18、ment is written in mandatory language. Acommentary to the mandatory language portion is provided for additionalinformation. Commentary provisions begin with an “R,” such as “R1.1.1,”and are shown in italics.Keywords: bar reinforcement; bar ribs; bond; development length; highrelative rib area; lap s
19、plice length.CONTENTSChapter 1Introduction, p. 408.3R-2Chapter 2Scope, p. 408.3R-2Chapter 3Notation and definitions, p. 408.3R-33.1Notation3.2DefinitionsChapter 4Development of high relative rib area bar reinforcement in tension, p. 408.3R-3Chapter 5Lap splices of high relative rib area bar reinforc
20、ement in tension, p. 408.3R-6Chapter 6References, p. 408.3R-76.1Referenced standards and reports6.2Cited referencesAppendix ARecommended supplement toASTM A615/A615M for high relative rib area bars, p. 408.3R-7A.1Requirements for deformationsA.2Relative rib areaA.3Type of steelA.4Referenced document
21、sTheresa M. Ahlborn David Darwin Neil M. Hawkins Max L. PorterGyorgy L. Balazs Richard A. Devries Roberto T. Leon Julio A. RamirezRobert W. Barnes Rolf Elighausen LeRoy A. Lutz John F. SilvaJoAnn P. Browning Anthony L. Felder Denis Mitchell Ahmet Koray TureyenDouglas B. Cleary Robert J. Frosch Strav
22、roula J. Pantazopoulou Jun ZuoJames V. Cox Bilal S. HamadAdolfo B. MatamorosChair408.3R-2 ACI COMMITTEE REPORTCHAPTER 1INTRODUCTIONThis guide is provided to help designers take advantage ofhigher bond strength exhibited by high relative rib area bars(Darwin and Graham 1993; Darwin et al. 1996a; Zuo
23、andDarwin 1998) in the calculation of tension lap splice lengthand development length of bar reinforcement. It includesexpressions for development and lap splice length applicableonly for high relative rib area bars. This document has beenupdated to reflect improvements to the provisions of ACI408.3
24、-01 (ACI Committee 408 2001) proposed by Darwin etal. (2005). Because experimental data are available only toevaluate the development and lap splice lengths of straighthigh relative rib area bars in tension, the integrity of highrelative rib area bars in compression or as hooked bars intension shoul
25、d be evaluated using appropriate Chapter 12provisions of ACI 318-08 (ACI Committee 318 2008).To use this guide, ASTM A615/A615M for carbon-steelreinforcing bars should have the supplementary require-ments imposed by the “Recommended Supplement toASTM A615/A615M for High Relative Area Bars” that isap
26、pended to this document. With modifications to thesection reference numbers, this supplement can beadapted for use with ASTM A706/A706M for low-alloysteel reinforcing bars.CHAPTER 2SCOPE2.1Evaluation of lap splice and development lengths ofcoated and uncoated bar reinforcement in tension shall belim
27、ited to bars having a high relative rib area, conforming toSections 2.1.1 through 2.1.5:2.1.1 The relative rib area is at least 0.10, but no largerthan 0.14;2.1.2 The ribs shall be in accordance with (a), (b), and (c).(a)Ribs shall be at an angle of 45 to 65 degrees inclusivewith respect to the axis
28、 of the bar;(b)Ribs shall not cross; and(c)Use of X patterns and diamond patterns for ribs is notpermitted.2.1.3 The rib spacing is at least 0.44 of the nominaldiameter dbof the bar reinforcement.2.1.4 The average rib width is not greater than one-third ofthe average rib spacing.2.1.5 The bar size d
29、oes not exceed No. 11 (No. 36).R2.1A high relative rib area bar is defined as a bar reinforce-ment with Rrgreater than or equal to 0.10, as conventionallydeformed reinforcement has relative rib areas of 0.06 to0.085. Based on available experimental results, the use ofthese provisions is limited to b
30、ar reinforcement with amaximum Rr= 0.14. Furthermore, consistent with thesmallest spacing used in tests, the rib spacing srshould notbe less than 44% of the nominal bar diameter, as indicatedin Section 2.1.3. A lower limit on width of the concretebetween ribs is indirectly prescribed in Section 2.1.
31、4 toavoid having a reduction in bond capacity due to a localshear failure of the concrete between the ribs. The variablesin Section 2.1.4 are illustrated in Fig. R2.1. For calculatingthe average rib width, the width at 0.75 of the rib height, asillustrated in Fig. R2.1, was chosen in the recommended
32、supplement to ASTM A615/A615M due to possible presenceof rounded corners on the ribs. The bar reinforcements usedin the experimental studies (Darwin and Graham 1993;Darwin et al. 1996a; Zuo and Darwin 1998) leading up to thisguide were either machined or special rolled; both bar typeshad ribs with f
33、lat outer faces. The supporting research results,therefore, are based on the actual width of the outer face.Bar with X and diamond deformation patterns areexcluded from this guide because their bond properties aremarkedly lower than bars with parallel ribs. Earlier bondstrength tests on X pattern No
34、. 6 and 11 (No. 19 and 36)epoxy-coated bars (Treece and Jirsa 1989) gave the lowestbond strengths reported in the literature, even though thebars had relative rib areas of 0.099 and 0.110, respectively.These bond values were significantly lower than valuesmeasured for epoxy-coated bars with parallel
35、 ribs and lowerrelative rib areas. Also, X pattern bars are not allowed in theCanadian Code (CSA 1992) because Canadian bond pullouttests on X pattern bars gave significantly lower strengthsthan did parallel rib bars. In addition to the bond strengthissue, a National Cooperative Highway Research Pro
36、gram(NCHRP) study (Helgason et al. 1976) indicated that Xpattern bars have lower fatigue life than bars with othertypes of deformation patterns.The bamboo pattern for ribs (ribs oriented at 90 degreesto the bar axis) are also excluded by the angle restrictionsadopted in this guide because of problem
37、s associated withthe bending of conventionally deformed bars with this riborientation.No. 11 (No. 36) bars were the largest high relative ribarea bars used in the experimental program that formed thebasis for these provisions. Thus, these provisions are notintended to be used for No. 14 and 18 (No.
38、43 and 57) bars.2.2The design provisions in this guide shall be used only tocalculate the development length or lap splice length of highrelative rib area bars in reinforced concrete members madewith normalweight concrete.Fig. R2.1Definition of average rib width.LAP SPLICE AND DEVELOPMENT LENGTH OF
39、HIGH RELATIVE RIB AREA REINFORCING BARS IN TENSION 408.3R-3R2.2The design provisions presented in this guide are intendedfor use in elements with normalweight concrete. The reasonfor this limitation in scope is that there is no research tosupport the validity of these design provisions in elementsma
40、de with other types of concrete. According to the defini-tion adopted in ACI 318-08, normalweight concrete typicallyhas a density (unit weight) between 135 and 160 lb/ft3(2155and 2555 kg/m3) and is normally taken as 145 to 150 lb/ft3(2315 to 2400 kg/m3).CHAPTER 3NOTATION AND DEFINITIONS3.1NotationAr
41、= projected rib area normal to bar reinforcementaxis, in.2(mm2)As= area of nonprestressed longitudinal tensionreinforcement, in.2(mm2)Atr= total cross-sectional area of all transverse reinforce-ment that is within the spacing s that crosses thepotential plane of splitting through the reinforcementbe
42、ing developed, in.2(mm2)CR= relative rib factor as defined by Eq. (4-4)cbb= clear cover of reinforcement being developed,measured to tension face of member, in. (mm)cmax= maximum value of csor cbb, in. (mm)cmin= minimum value of csor cbb, in. (mm)cs= minimum value of csi+ 0.25 in. (6 mm) or cso, in.
43、(mm); csimay be used instead of csi+ 0.25 in. tocompute cscsi= one-half of average clear spacing between bars orlap splices in a single layer, in. (mm)cso= clear cover of reinforcement being developed or lapspliced, measured to side face of member, in. (mm)db= nominal bar diameter, in. (mm)fc=specif
44、ied compressive strength of concrete, psi(MPa)fc1/4= fourth root of fc, expressed in psi (MPa) unitsfct= average splitting tensile strength of lightweightaggregate concrete, psi (MPa)fy= specified yield strength of reinforcement beinglap spliced or developed, psi (MPa)Ktr=transverse reinforcement in
45、dex for high relativerib area bars as defined by Eq. (4-3)ld= development length in tension of deformed bar,in. (mm)ls= lap splice length in tension of deformed bar, in.(mm)n = number of bars being developed or lap splicedalong plane of splittingRr= relative rib area; ratio of projected rib area nor
46、malto bar axis to product of nominal bar perimeterand average center-to-center rib spacings = maximum center-to-center spacing of transversereinforcement within ld or ls, in. (mm)e= factor used to modify development length basedon reinforcement coating; see Section 4.3.t= factor used to modify devel
47、opment length basedon reinforcement location; see Section 4.3.c= factor used to modify development length basedon cover and/or spacing perpendicular to controllingcover and/or spacing; see Section 4.2.R3.1NotationAb= area of an individual bar, in.2(mm2)Ar= projected rib area normal to reinforcing ba
48、r axis,in.2(mm2)hr= average height of deformations, in. (mm)sr= average center-to-center rib spacing, in. (mm)In the notation section it is stated that, for the purpose ofcalculating the value of cs, it is permitted to use csiinsteadof csi+ 0.25. This is provided for simplification. Use of csiinstea
49、d of csi+ 0.25 results in a value of csthat is less, andconsequently produces a more conservative development orlap splice length.3.2Definitionshigh relative rib area barsdeformed bar reinforcementwith a relative rib area equal to 0.10 or larger.normalweight concreteconcrete containing onlyaggregate that conforms to ASTM C33/C33M.relative rib arearatio of projected rib area normal tobar axis to product of nominal bar perimeter and averagecenter-to-center rib spacing.ribtransverse protrusion or deformation on a deformedbar. The term “rib” is used uniforml
