1、ACI 408.2R-12Report on Bond of Steel Reinforcing Bars Under Cyclic LoadsReported by Joint ACI-ASCE Committee 408First PrintingSeptember 2012Report on Bond of Steel Reinforcing Bars Under Cyclic LoadsCopyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This materia
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11、e Practice (MCP).American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgISBN 13: 978-0-87031-779-8 ISB: 0-87031-779-2This report summarizes research on bond strength and behavior of steel reinforcing bars under cyclic lo
12、ads. The report provides a background to bond problems, discusses the main variables affecting bond performance, and describes bond behavior under cyclic loads. Two general types of cyclic loads are addressed: high-cycle (fatigue) and low-cycle (earthquake and similar). The anchorage behaviors of st
13、raight bars, hooked bars, and lap splices are included. Analytical bond models are described, design recom-mendations are provided for both high- and low-cycle fatigue, and suggestions for further research are given.Keywords: anchorage; bar slip; bond; bond models; cyclic loads; design recommendatio
14、ns; development length; fatigue; hooks; earthquake loads; splices.CONTENTSChapter 1Introduction and scope, p. 21.1Introduction1.2ScopeChapter 2Notation and definitions, p. 32.1Notation2.2DefintionsChapter 3Bond and anchorage, p. 43.1Average bond stresses3.2Components of bond resistance3.3Failure mod
15、es3.4Bond mechanisms3.5Factors affecting bond strength under cyclic loads3.6SummaryACI 408.2R-12Report on Bond of Steel Reinforcing Bars Under Cyclic LoadsReported by Joint ACI-ASCE Committee 408Adolfo B. MatamorosChairMichael Keith ThompsonSecretaryTheresa M. AhlbornRobert W. Barnes*Jean-Jacques Br
16、aunJoAnn P. BrowningJames L. CaldwellDouglas B. Cleary*Louis J. ColarussoJames V. CoxChristian DahlDavid DarwinRichard A. DevriesRolf EligehausenAlvin C. EricsonAnthony L. FelderScott K. GrahamBilal S. HamadNeil M. HawkinsSteven E. HoldsworthJames M. LaFaveRoberto T. LeonLeRoy A. LutzStavroula J. Pa
17、ntazopoulouMax L. PorterJulio A. RamirezJohn F. SilvaRobert G. SmithAhmet Koray Tureyen*William H. Zehrt Jr.Jun ZuoConsulting membersGyorgy L. BalazsWilliam C. GallenzBrian C. GerberAllen J. HulshizerKenneth A. LuttrellDenis MitchellMikael P. J. OlsenConrad PaulsonMelvyn PreciousRichard A. Ramsey*Me
18、mber, Subcommittee on Repeated Load Effects Chair and Editor, Subcommittee on Repeated Load Effects Note: The contributions of Brett Baker are gratefully acknowledged.1ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construc
19、tion. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all respo
20、nsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall
21、 be restated in mandatory language for incorporation by the Architect/Engineer.ACI 408.2R-12 superseds ACI 408.2R-92 and was adopted and published September 2012.Copyright 2012, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any means, incl
22、uding the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual repro-duction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.Chapter
23、 4Bond behavior under cyclic loads, p. 94.1High-cycle fatigue4.2Correlation between fatigue and sustained loading4.3Low-cycle loading4.4Influence of cracking on bond strength4.5Debonding to increase shear strength at connectionsChapter 5Anchorage under high-cycle fatigue, p. 135.1Straight bar anchor
24、ages5.2Hooked bar anchorages5.3Lap splicesChapter 6Anchorage under low-cycle loading, p. 176.1Straight bar anchorages6.2Hooked bar anchorages6.3Lap splicesChapter 7Analytical bond models, p. 227.1Early models of local bond behavior7.2Models for local bond-slip effects7.3Contribution of bond-slip for
25、 modeling member and structural system behavior7.4Bond modeling used in evaluation of existing structures with short lap splices or discontinuous bottom bars through joints7.5Modeling of high-cycle (fatigue) loadingChapter 8Design and analysis approaches, p. 248.1High-cycle fatigue8.2Low-cycle loadi
26、ng (earthquake loads)8.3RecommendationsChapter 9Conclusions and recommendations, p. 299.1Monotonic loading9.2Cyclic loading9.3Recommendations for future researchChapter 10References, p. 30CHAPTER 1INTRODUCTION AND SCOPE1.1IntroductionThe transfer of forces across the interface between concrete and s
27、teel by bond stresses is of fundamental importance to many aspects of reinforced concrete behavior. Satisfactory bond performance is an essential goal in detailing reinforce-ment in structural components. Many detailing provisions in ACI 318 are aimed at preventing bond failures.Bond stresses in rei
28、nforced concrete members arise from two distinct situations. The first is anchorage or development where bars are terminated. The second is flexural bond or the change of force along a bar due to a change in bending moment along the member. Bond performance under static monotonically increasing defo
29、rmationsreferred to as monotonic loadinghas been summarized in ACI 352R, ACI 408R, and ACI Committee 408 (1966, 1970, 1979). Bond behavior under cyclic loads received little attention until design for earthquake and wave loads became impor-tant design topics (ACI Committee 408 1979). Investigations
30、over the past 40 years have clarified some of the important parameters influencing bond behavior under cyclic loads. However, the influence of many of these parameters is understood only qualitatively.In this report, “bar” means “reinforcing bar” and “ribs” refer to the deformations on deformed rein
31、forcing bars. Longitudinal deformations on reinforcing bars are not clas-sified as ribs. “Bond stress” refers to the stresses along the bar-concrete interface. The steel stresses along the length of the reinforcing bar are modified by transfer of force between the bar and the surrounding concrete al
32、ong the interface (refer to Fig. 1.1).The change in bar tensile force DF between two cracked sections along a flexural member DF is given byFTTMjdMjd=121122(1.1a)The average bond stress ubis usually expressed asFig. 1.1Definition of bond stress.American Concrete Institute Copyrighted Materialwww.con
33、crete.org2 REPORT ON BOND OF STEEL REINFORCING BARS UNDER CYCLIC LOADS (ACI 408.2R-12)uqFLfdLddfLboosbbbs= =()()=pipi244(1.1b)Cyclic loadings are divided into two general categories. The first is designated low-cycle or low-cycle, high-stress loading, or a load history containing less than 100 cycle
34、s and having bond stress ranges (ur) greater than 600 psi (4 MPa). Low-cycle loadings commonly result from earthquake and high-wind loadings. The second category is designated high-cycle or fatigue loading with a load history containing thou-sands or millions of cycles, but at a low bond stress rang
35、e (ur) typically less than 300 psi (2 MPa). Bridge members, offshore structures, and members supporting vibrating machinery are often subjected to high-cycle or fatigue loading. High-cycle loadings can be a problem at service load levels whereas low-cycle loadings can produce prob-lems at the ultima
36、te limit state.Bond behavior under cyclic loading can further be subdi-vided according to the type of stress applied. The first is repeated or unidirectional loading, which implies that the bar stress does not reverse from tension to compression during a load cycle, the usual situation for fatigue l
37、oading. The second is stress reversal, where the bar is subjected alterna-tively to tension and compression. Earthquake loading typi-cally causes stress reversals.1.2ScopeThis report reviews bond and anchorage of steel reinforcing bars in normal and lightweight concrete, with emphasis on bond under
38、cyclic loading. Although the amount of informa-tion about the bond behavior of epoxy-coated reinforcing bars subjected to cyclic loading is limited, available refer-ences on this topic were reviewed and are presented in the document. Bond and anchorage of prestressing steel and headed reinforcing ba
39、rs are not addressed in this report. This report serves both designers and researchers, and is orga-nized accordingly. Chapters 3 and 4 present background information on the issue of bond under cyclic loading. Chap-ters 5, 6, and 7 deal with results of research and development of analytical bond mod
40、els. Chapters 8 and 9 review inter-national design guidelines dealing with bond under cyclic loads and should be of interest to designers. This report also introduces designers to the basic mechanisms involved in bond, the variables that affect those mechanisms, and differ-ences in bond behavior und
41、er cyclic and noncyclic loads.CHAPTER 2NOTATION AND DEFINITIONS2.1NotationAb= cross-sectional area of reinforcing bar, in.2(mm2)Ac= area of concrete cross section, in.2(mm2)Atr= area of transverse reinforcement, in.2(mm2)BI = representation of the severity of bond stresses rela-tive to the bond stre
42、ngthC = concrete cover, in. (mm)cb= smaller of: (a) the distance from center of a bar or wire to nearest concrete surface; and (b) one-half the center-to-center spacing of bars or wires being developed, in. (mm)D = development length according to AIJ (1990), in. (mm)DCH = ductility class high, based
43、 on the maximum behavior factorDCM = ductility class medium, based on the maximum behavior factord = depth from extreme compression fiber to centroid of tensile reinforcement, in. (mm)db= diameter of bar, or diameter of bar being developed, in. (mm)dbL= nominal diameter of longitudinal bars, in. (mm
44、)fb= static bond strength as used for offshore structures, psi (MPa)fbr= bond strength at 2,000,000 cycles as used for offshore structures, psi (MPa)fc = specified concrete compressive strength, psi (MPa)fcd= design concrete compressive strength, psi (MPa)fcr= stress range in concrete, psi (MPa)fctm
45、= mean value of the tensile strength of concrete, psi (MPa)fmin= minimum stress level, ksi (MPa)fr= stress range due to live loads and impact recom-mended by AASHTO, ksi (MPa)frup= static modulus of rupture, psi (MPa)fs= existing reinforcement strength based on available development length, psi (MPa
46、)fsos= yield strength divided by a factor of safety (typi-cally = 1.15), offshore structures, psi (MPa)fy= yield strength of bar being developed, psi (MPa)fyd= design value of the yield strength of bars, psi (MPa)fyt= yield strength of transverse reinforcement, psi (MPa)h = depth of member, in. (mm)
47、hc= width of the column parallel to the bars, in. (mm)hj= joint dimension parallel to the bar, in. (mm)jdi= internal moment arm at section i, in. (mm)Ktr= transverse reinforcement indexkD= factor reflecting the ductility class equal to 1 for DCH and to 2/3 for DCMl = total length of the member, in.
48、(mm)lb= provided length of straight development, lap splice, or standard hook, in. (mm)ld= development length, in. (mm)ld = equivalent straight bar anchorage length corre-sponding to a hooked bar anchorage, in. (mm)ldh= lead embedment length for a hook, in. (mm)le= length of embedment of reinforceme
49、nt, in. (mm)Mi= moment at section i, lb-in. (N-m)N = number of cycles to failureNed= design axial force, lbf (N)q = change of bar force per unit length of bar, lb/in. (N/mm)r/h = ratio of base radius to height of rolled transverse ribS = applied stress range, psi (MPa)Sbmax= maximum bond strength as used for offshore struc-tures, psi (MPa)Sbr= stress range as used for offshore structures, psi (MPa)American Concrete Institute Copyrighted Materialwww.concrete.orgREPORT ON BOND OF STEEL REINFORCING BARS UNDER CYCLI
