ACI 334.1R-1992 Concrete Shell Structures Practice and Commentary《混凝土壳面结构规范和注释》.pdf

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1、ACI 334.1R-92 replaces 334.1R-64 (Revised 1982)(Reapproved 1996) and becameeffective March 1, 1992. The 1992 revision included minor editorial corrections andthe deletion of the year designation for ACI 318 to make the current code the appli-cable reference.Copyright 1992, American Concrete Institut

2、e.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies 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 sys

3、tem or device, unless permission inwriting is obtained from the copyright proprietors.334.1R-1ACI Committee Reports, Guides, Manuals, and Commentariesare intended for guidance in planning, designing, executing,and inspecting construction. This document is intended for theuse of individuals who are c

4、ompetent to evaluate thesignificance and limitations of its content and recommendationsand who will accept responsibility for the application of thematerial it contains. The American Concrete Institute disclaimsany and all responsibility for the stated principles. The Instituteshall not be liable fo

5、r any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found 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/Enginee

6、r.Concrete Shell StructuresPractice and CommentaryReported by Joint ACI-ASCE Committee 334ACI 334.1R-92(Reapproved 2002)A report on the practical aspects of shell design including recommenda-tions and a commentary for designers of thin concrete shells. Generalguidance based on current practice is gi

7、ven on analysis, proportioning,reinforcing, and construction. A selected bibliography on analyticalmethods featuring design tables and aids is included to assist the engineer. Keywords: aggregate size; buckling; construction; design: double-curvatureshell; edge beam; folded plate; formwork; model; p

8、restressing; reinforce-ment; shell; single-curvature shell; splice; stiffening member; supportingmember; thickness; thin shell.CONTENTSPreface, p. 334.1R-2PART ICRITERIAChapter 1General, p. 334.1R-21.1Definitions1.2ScopeChapter 2Analysis, p. 334.1R-22.1Assumptions2.2Analysis of thin shells2.3Analysi

9、s of supporting members2.4Model analysisChapter 3Stability analysis, p. 334.1R-33.1BucklingCommittee members voting on the 1992 revisions:Frank Baron John V. Christiansen Milo S. Ketchum, Jr. John B. SkillingDavid P. Billington Willhelm Flgge James A. McCarthy Bruno ThurlimannRichard R. Bradshaw Ric

10、hard M. Gensert Stefan J. Medwadowski Robert ZaborowskiFelix Candela Otto Gruenwald Mario G. SalvadoriPhillip L. GouldChairmanStuart E. SwartzSecretaryJack Christiansen Ajaya K. Gupta Stefan J. Medwadowski David B. SouthJohn F. Abel Robert B. Haber Luis F. Meyer Anton TedeskoDavid P. Billington Kye

11、J. Han Eldon F. Mockry Bing-Yuan TingArthur J. Boyt, Jr. Harry G. Harris John K. Parsons Daniel F. TullyEli W. Cohen Mark A. Ketchum William C. Schnobrich Arnold WilsonMorris N. Fialkow Milo S. Ketchum Alexander ScordelisAnton TedeskoChairmanEric C. MolkeVice ChairmanAlfred L. ParmeSecretary334.1R-2

12、 MANUAL OF CONCRETE PRACTICEChapter 4Proportioning, p. 334.1R-34.1Allowable stresses and load factors4.2Shell thickness4.3Shell reinforcement4.4Prestressing4.5Concrete cover over reinforcementChapter 5Construction, p. 334.1R-45.1Aggregate size5.2FormsPART IICOMMENTARYChapter 1General, p. 334.1R-4Cha

13、pter 2Analysis of shell, p. 334.1R-42.1Thin shells of single curvature2.2Folded plates2.3Thin shells of double curvatureChapter 3Analysis of supporting members,p. 334.1R-5Chapter 4Prestressing, p. 334.1R-6Chapter 5Stability, p. 334.1R-6Chapter 6Proportioning, p. 334.1R-7Chapter 7Construction, p. 334

14、.1R-77.1Forms and decentering7.2Concrete placing7.3Curing of concreteChapter 8Models, p. 334.1R-7Chapter 9Standards and ACI documents cited in this report, p. 334.1R-8PART IIISELECTED BIBLIOGRAPHYPREFACEWith the increased use of thin shells has come an increasedunderstanding of their behavior throug

15、h field observations,laboratory tests, and mathematical refinement of analyticprocedures. However, because of the wide range of geometrypossible with thin shells, the accumulated understanding isstill limited. For some thin shell systems, such as cylindricalbarrel shells, the design can be made with

16、 the same degree ofaccuracy as for conventional reinforced concrete construction.For other thin shell systems, such as those of doublecurvature, the design must be at times based on less-refinedanalyses in the same sense as the empirical design of flatplate floors. Therefore, it was felt desirable t

17、o divide thisreport into two parts.The first part, entitled “Criteria,” covers general designrecommendations. The second part, entitled “Commentary,”contains data of general interest to the designers of thinshells and reflects current practice. A “Selected Bibliog-raphy” is included as reference mat

18、erial on current methodsof analysis.The analysis, design, and construction of thin shell structuresrequires a thorough knowledge in this field. Therefore, therecommendations contained herein are not sufficient in them-selves for the satisfactory execution of thin shell structures.Designers are refer

19、red to the many texts and technical papersthat are readily available.PART ICRITERIACHAPTER 1GENERAL1.1Definitions1.1.1 Thin shellsCurved or folded slabs whose thick-nesses are small compared to their other dimensions. Theyare characterized by their three-dimensional load-carryingbehavior, which is d

20、etermined by their geometrical shape,their boundary conditions, and the nature of the applied load.Thin shells are usually bounded by supporting members andedge members.1.1.2 Auxiliary membersIn a broad sense, any memberlocated along the boundary of a shell or shell segment, witha capacity to stiffe

21、n the shell and distribute or carry load incomposite action with the shell. They are classified as followsin accordance with established usage, although for certainshells a member may serve in a combination of capacities:a) Supporting membersBeams, arches, trusses,diaphragms, etc., along the edges o

22、f thin shells thatserve both to support and to stiffen the thin shell.b) Edge membersBeams, trusses, etc., along the edges ofthin shells that do not form part of the main supportingstructure, but serve to stiffen and act integrally, that is,in composite action with the thin shell to carry loads toth

23、e supporting members.c) Stiffening membersRibs that serve only to stiffen thethin shell or to control local deformations.1.1.3 Elastic analysisAny structural analysis based onelastic behavior and involving assumptions that are suitableto approximations of three-dimensional elastic behavior.Analyses

24、based on the results of elastic model tests, whenconducted properly, are considered as valid elastic analyses.1.2Scope1.2.1 These recommendations cover the design of thinshell concrete structures and only apply to the thin shellportions of such structures unless otherwise stated.1.2.2 All applicable

25、 sections of the ACI Building Code(ACI 318), including the precast and prestressed concretesections of the Code, should be followed in the design ofshell structures except where they conflict with the followingprovisions.CHAPTER 2ANALYSIS2.1Assumptions2.1.1 For an elastic analysis, concrete may be a

26、ssumeduncracked, homogeneous, and isotropic.2.1.2 Poissons ratio may be assumed equal to zero.2.2Analysis of thin shells2.2.1 Elastic behavior is the commonly accepted basis fordetermining stresses, displacements, and stability of thin shells.CONCRETE SHELL STRUCTURESPRACTICE AND COMMENTARY 334.1R-3

27、2.2.2 The rigor and the necessary degree of accuracyrequired in the analysis of any specific thin shell structuredepend on certain critical factors. These include: the configu-ration of the surface and the degree of curvature (geometry), thesize of the structure, the type of boundary conditions, and

28、 thenature of the loading. Because of the complex interrelationshipbetween these factors, specific recommendations regardingrigor and accuracy of analysis are not given.2.2.3 Approximate methods of analysis that do not satisfycompatibility of strains or stresses in the shell may be usedin cases wher

29、e authoritative sources and experience haveshown them to be applicable within the range employed.2.2.4 Equilibrium checks of internal stresses and externalloads are to be made to insure consistency of results.2.2.5 An ultimate strength analysis may be used only as acheck on the adequacy of the desig

30、n. It is not to be used as asole criterion for design, except where it can be proven to beapplicable.2.3Analysis of supporting members2.3.1 Supporting members shall be designed in accordancewith a recognized elastic analysis.2.3.2 A portion of the thin shell shall be assumed to actwith the supportin

31、g member.2.4Model analysis2.4.1 Models may be used as the basis for a design and/orto check the validity of assumptions involved in a mathematicalanalysis. When models are used, only those portions thatsignificantly affect the items under study need be simulated.Every attempt must be made to ensure

32、that these tests revealthe quantitative behavior of the prototype structure.CHAPTER 3STABILITY ANALYSIS3.1Buckling3.1.1 When investigating shells for stability, considerationshall be given to the possible reduction in the value of thebuckling load caused by large deflections, creep effects, andthe d

33、eviation between the actual and theoretical shell surface.CHAPTER 4PROPORTIONING4.1Allowable stresses and load factors4.1.1 Unless otherwise stated, concrete and steel stressesand load factors will be as specified in the Building Code(ACI 318).4.1.2 Minimum standard cylinder strength fc shall be3000

34、 psi.4.2Shell thickness4.2.1 Shell thickness is not always dictated by strengthrequirements but often by deformation of edge members,stability, and cover over reinforcing steel.4.2.2 Stress concentrations due to abrupt changes insection shall be considered and, where necessary, the thinshell shall b

35、e gradually thickened.4.3Shell reinforcement4.3.1 The stress in the reinforcement may be assumed at theallowable value independently of the strain in the concrete.4.3.2 Where the tensile stresses vary greatly in magnitudeover the shell, as in the case of cylindrical shells, the reinforce-ment capabl

36、e of resisting the total tension may be concentratedin the region of maximum tensile stress. Where this is done,the percentage of crack control reinforcing in any 12 in.width of shell shall be not less than 0.35% throughout thetensile zone.4.3.3 The principal tensile stresses shall be resistedentire

37、ly by reinforcement.4.3.4 Reinforcement to resist the principal tensile stresses,assumed to act at the middle surface of the shell, may beplaced either in the general direction of the lines of principaltensile stress (also referred to as parallel to the lines of principaltensile stress), or in two o

38、r three directions. In the regions ofhigh tension it is advisable, based on experience, to place thereinforcing in the general direction of the principal stress.4.3.5 The reinforcement may be considered parallel to theline of principal stress when its direction does not deviatefrom the direction of

39、the principal stress more than 15 degrees.Variations in the direction of the principal stress over thecross section of a shell due to moments need not be consideredfor the determination of the maximum deviation. In areaswhere the stress in the reinforcing is less than the allowablestress, a deviatio

40、n greater than 15 degrees can still beconsidered parallel placing; a stress decrease of 5% shall beconsidered to compensate for each additional degree of deviationabove 15 degrees. Wherever possible, such reinforcing mayrun along lines considered most practical for construction, suchas straight line

41、s.4.3.6 Where placed in more than one direction, the reinforce-ment shall resist the components of the principal tensionforce in each direction.4.3.7 In those areas where the computed principal tensilestress in the concrete exceeds 300 psi, placement of at leastone layer of the reinforcing shall be

42、parallel to the principaltensile stress, unless it can be proven that a deviation of thereinforcing from the direction parallel to the lines of prin-cipal tensile stress is permissible because of the geometricalcharacteristics of a particular shell and because for reasons ofgeometry only insignifica

43、nt and local cracking could develop.4.3.8 Where the computed principal tensile stress (psi) inthe concrete exceeds the value 2 (where fc is also inpsi), the spacing of reinforcement shall not be greater thanthree times the thickness of the thin shell. Otherwise the rein-forcement shall be spaced at

44、not more than five times thethickness of the thin shell, nor more than 18 in.4.3.9 Minimum reinforcement shall be provided asrequired in the Building Code (ACI 318) even where notrequired by analysis.4.3.10 The percentage of reinforcement in any 12 in. widthof shell shall not exceed 30fc /fs. Howeve

45、r, the maximumpercentage shall not exceed 6% if fs= 20,000 psi, 5% if fs=25,000 psi, or 4% if fs = 30,000 psi when the latter values areacceptable. If the deviation of the reinforcing from the lines ofprincipal stress is greater than 10 deg, the maximum percentageshall be one-half of the above value

46、s.4.3.11 Splices in principal tensile reinforcement shall bekept to a practical minimum. Where necessary they shall befc334.1R-4 MANUAL OF CONCRETE PRACTICEstaggered with not more than 1/3 of the bars spliced at anyone cross section. Bars shall be lapped only within the samelayer. The minimum lap fo

47、r shell reinforcing bars, wheredraped, shall be 30 diameters with a 1 ft 6 in. minimumunless more is required by the Building Code (ACI 318),except that the minimum may be 12 in. for reinforcement notrequired by analysis. The minimum lap for welded wirefabric shall be 8 in. or one mesh, whichever is

48、 greater, exceptthat Building Code requirements shall govern where the wirefabric at the splice must carry the full allowable stress.4.3.12 The computed stress of the shell reinforcing at thejunction of shell and supporting member or edge membershall be developed by anchorage within or beyond the wi

49、dthof the member.4.3.13 Reinforcement to resist bending moments shall beproportioned and provided in the conventional manner withproper allowance for the direct forces.4.4Prestressing4.4.1 Where prestressing tendons are draped within a thinshell, the resulting tendon profile not lying in one plane willexert a force on the shell which can be resolved into compo-nents. The design shall account for these force components.4.4.2 Where prestressing tendons are anchored, specialreinforcing shall be added to assure that no local over