1、ACI ITG-5.2-09Requirements for Design of a SpecialUnbonded Post-Tensioned PrecastShear Wall Satisfying ACI ITG-5.1(ACI ITG-5.2-09) and CommentaryReported by ACI Innovation Task Group 5An ACI StandardAmerican Concrete InstituteAdvancing concrete knowledgeRequirements for Design of a Special Unbonded
2、Post-Tensioned Precast Shear WallSatisfying ACI ITG-5.1 (ACI ITG-5.2-09) and CommentaryFirst printingAugust 2009ISBN 978-0-87031-339-4Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This materialmay not be reproduced or copied, in whole or part, in any printe
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11、titute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701www.concrete.orgACI ITG-5.2-09 was adopted May 4, 2009 and published August 2009.Copyright 2009, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or b
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13、tors.ITG-5.2-1ACI Committee Reports, Guides, Manuals, StandardPractices, and Commentaries are intended for guidance inplanning, designing, executing, and inspecting construction.This Commentary is intended for the use of individuals whoare competent to evaluate the significance and limitations of it
14、scontent and recommendations and who will acceptresponsibility for the application of the material it contains.The American Concrete Institute disclaims any and allresponsibility for the stated principles. The Institute shall notbe liable for any loss or damage arising therefrom.Reference to this Co
15、mmentary shall not be made in contractdocuments. If items found in this document are desired by thelicensed design professional to be a part of the contractdocuments, they shall be restated in mandatory language.Requirements for Design of a Special UnbondedPost-Tensioned Precast Shear Wall Satisfyin
16、gACI ITG-5.1 (ACI ITG-5.2-09) and CommentaryAn ACI StandardReported by ACI Innovation Task Group 5ACI ITG-5.2-09This standard defines procedures that may be used to design specialprecast concrete shear walls, coupled or uncoupled, composed ofdiscretely jointed precast panels that are vertically post
17、-tensioned to thefoundation with unbonded tendons. Such walls are suitable for use inregions of high seismicity and for structures assigned to high seismicdesign categories. After a major seismic event, these walls can be expectedto exhibit minimal damage in the flexural hinging region at the base o
18、f thewall as well as negligible permanent displacements. Such walls do notsatisfy the prescriptive requirements of Chapter 21 of ACI 318-05 for shearwalls of monolithic construction. According to 21.2.1.5 of ACI 318-05, theiracceptance requires demonstration by experimental evidence and analysisthat
19、 the walls have strength and toughness equal to or exceeding thoseprovided by comparable monolithic reinforced concrete walls that satisfythe prescriptive requirements of Chapter 21. This standard describes theprocedures that the designer may use to demonstrate, through analysis,that one type of unb
20、onded post-tensioned precast wall has strength and tough-ness at least equal to that of comparable special reinforced concrete monolithicwalls. The standard consists of Design Requirements and a Commentary.Among the subjects covered in these Design Requirements are requirementsfor:1. Materials, incl
21、uding considerations for the coupling or connectiondevices, that provide the primary source of energy dissipation for the wall system;2. Individual walls, including considerations to ensure ductility,energy dissipation, integrity, stiffness, and strength; and3. Coupled walls, including consideration
22、s of the roles of the post-tensioning tendons and coupling devices in providing energy dissipation,and strength and stiffness for coupled walls greater than the sum of thoseprovided by the coupled walls acting as separate units.The Commentary references documentary evidence, additional to thereferen
23、ces of ACI ITG-5.1-07 and Chapter 21 of ACI 318R-05, that supportsthese Design Requirements. In this standard, however, no comparison ismade between the performance of precast test modules satisfying theprescriptive requirements of ACI 318 and modules satisfying these DesignRequirements but not sati
24、sfying ACI 318. Such comparisons, both experi-mental and analytical, are available in the cited references.All references to ACI 318 and ACI 318R in these Design Requirementsand Commentary refer to ACI 318-05 unless another edition of ACI 318 isspecifically designated. All references to ASCE/SEI 7 i
25、n these DesignRequirements and Commentary are to ASCE/SEI 7-05, includingSupplement No. 1.In this standard, consistent with the format of ACI 318-05, the word“Section” is not included before a reference to a section of ACI 318-05. Tomore clearly designate a section in this standard, however, the wor
26、d“Section” is used before any reference to a section of this standard.Consistent with the format of ASCE/SEI 7-05, the word “Section” isincluded before a reference to a section of ASCE/SEI 7-05.Keywords: coupling devices; drift angle; energy dissipation; lateral resis-tance; post-tensioning; precast
27、 concrete; prestressed concrete; seismicdesign; special shear wall; test module; toughness.Attila B. Beres Ronald Klemencic Stephen P. Pessiki John W. WallaceNed M. Cleland Vilas S. Mujumdar Carol K. Shield Loring A. Wyllie, Jr.Neil M. Hawkins Suzanne Dow NakakiConsulting memberS. K. GhoshCharles W.
28、 DolanChairITG-5.2-2 ACI STANDARDCONTENTSChapter 1General, p. ITG-5.2-21.1Introduction1.2Scope1.3DrawingsChapter 2Notation and definitions, p. ITG-5.2-52.1Notation2.2DefinitionsChapter 3Materials, p. ITG-5.2-73.1General3.2Ducts3.3Reinforcement3.4Concrete3.5Interface grout3.6Coupling devices3.7Corros
29、ion protection of prestressing tendonsChapter 4Structural system requirements for walls, p. ITG-5.2-94.1General4.2Strength4.3Drift4.4Wall characteristics4.5Distribution of walls within structures4.6Wall system-gravity load frame interactionsChapter 5Design requirements for uncoupled wall systems, p.
30、 ITG-5.2-125.1Scope5.2Materials5.3Prestress force5.4Energy-dissipating reinforcement5.5Shear strength5.6Flexural strength and drift limits5.7Detailing of lowermost wall panel5.8Interface groutChapter 6Design requirements for coupled wall systems, p. ITG-5.2-166.1Scope6.2Materials6.3Coupling devices6
31、.4Prestress force6.5Shear strength6.6Flexural strength and drift limits6.7Lowermost panel6.8Interface groutChapter 7Design requirements for coupling devices, p. ITG-5.2-187.1Scope7.2General7.3Materials7.4Design methodologyChapter 8References, p. ITG-5.2-198.1Referenced standards and reports8.2Cited
32、referencesCHAPTER 1GENERAL1.1IntroductionFor regions of high seismic risk, where structures assignedto Seismic Design Category (SDC) D, E, or F shall be used,21.2.1.5 of ACI 318 permits the use of structural systems thatdo not meet the prescriptive requirements of Chapter 21 ifcertain experimental e
33、vidence and analysis are provided (allreferences to ACI 318 and ACI 318R in this standard refer toACI 318-05 unless another edition of ACI 318 is specificallydesignated). The intent of ACI ITG-5.1 is to define theminimum experimental evidence that is deemed sufficient topermit the use of unbonded po
34、st-tensioned precast structuralwall systems, in accordance with 21.2.1.5 of ACI 318, whenthose systems do not satisfy fully the prescriptive require-ments for wall systems in Chapter 21 of ACI 318.Before validation testing can be undertaken, ACI ITG-5.1requires that a design procedure be developed f
35、or prototypewall systems having the generic form for which acceptanceis sought, and that design procedure is used to proportion thetest modules. This standard defines the design procedure fora specific type of wall system that does not satisfy theprescriptive requirements of Chapter 21 of ACI 318, b
36、ut isvalidated for use in regions of high seismicity under ACIITG-5.1. The wall system uses precast concrete panels thatare post-tensioned to the foundation and intended to rock onthat foundation under seismic actions.For coupled walls, coupling devices located along thevertical boundaries of adjace
37、nt walls provide the requiredenergy dissipation and energy-dissipating reinforcement thatcrosses the wall-foundation interface is unnecessary. Duringan earthquake, the coupled walls displace as rigid bodies thatare tied together. Wall deformations occur primarily at theinterface between each individ
38、ual wall and the foundation,with each wall rocking separately at that interface.The unbonded post-tensioning has two purposes. First, thepost-tensioning steel is deliberately designed to remainessentially elastic during the design basis earthquake (DBE),defined in ASCE/SEI 7, so that it forces the w
39、alls to return totheir undeformed positions following the event. Second, thefriction induced by the post-tensioning and gravity loadingon the wall transfers the horizontal shears due to lateral loadingsat the interfaces between the wall and the foundation andbetween the precast panels of the wall.Th
40、e detailing procedures described in this standard are forone specific type of unbonded post-tensioned precast shearwall system, coupled or uncoupled. Four statements definekey characteristics of uncoupled and coupled unbondedpost-tensioned precast concrete cantilever shear walls thatsatisfy this sta
41、ndard:(a) Post-tensioning tendons unbonded from an anchor inthe foundation to an anchor at the top of the wall and locatedin a single duct on the vertical centerline of the wall or, ifneeded, in two or more ducts positioned symmetrically oneither side of that vertical centerline and within 10% of th
42、ewall length from that centerline;(b) Precast panels one story or more in height; and(c) For uncoupled walls, two sets of energy-dissipatingreinforcing bars crossing the interface between the lower-DESIGN REQUIREMENTS OF SHEAR WALL SATISFYING ACI ITG-5.1 ITG-5.2-3most precast panel of the wall and t
43、he foundation and withthe sets located symmetrically about the vertical centerlineof the wall; or(d) For coupled walls, energy-dissipating coupling devicesfor a given vertical joint between coupled walls, of equalstrength, at least two in number for each coupled edge of apanel in the wall, and posit
44、ioned so that the width of thevertical joint between panels remains approximatelyconstant in width as the walls rock on their bases.R1.1Large-scale laboratory experiments (Bora et al. 2007;Perez et al. 2003; Priestley et al. 1999; Rahman andRestrepo 2000; Santana 2005) have shown that unbondedpost-t
45、ensioned precast concrete cantilever shear walls canprovide safety and serviceability levels, during and after anearthquake, that meet or exceed performance levels requiredby 21.2.1.5 of ACI 318 and ACI ITG-5.1. Analytical studies(Kurama 2002; Perez et al. 2004a,b; Rahman and Restrepo2000; Stanton a
46、nd Nakaki 2002; Thomas and Sritharan2004; Sritharan et al. 2007) have shown that to achieve suchperformance levels, the shear walls should be proportionedand detailed in accordance with specific considerations.This standard is developed from the aforementioned studiesand related references. This sta
47、ndard contains the minimumrequirements for ensuring that one type of unbonded post-tensioned precast concrete cantilever shear wall system,uncoupled or coupled, can sustain a series of oscillations intothe inelastic range of response without critical decay in strengthor excessive story drifts. Furth
48、er, that shear wall should showonly minimal or no damage to the wall, and minimal or nopermanent displacements after the oscillations cease.In this specific type of coupled or uncoupled wall system,the post-tensioning tendons are unbonded and designed toremain elastic during the DBE. Except at the f
49、oundation, thehorizontal joints between the precast panels that make up acantilever wall are designed to remain closed during anearthquake.For uncoupled walls, vertical reinforcing bars groutedinto ducts located in the wall panels abutting the foundationand in the foundation, and described in this standard asenergy-dissipating reinforcement, provide energy dissipationas they yield alternately in tension and compression duringan earthquake. These bars also provide continuity additionalto the post-tensioning between the cantilever wall and the
