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1、ACI 349.1R-07 Reinforced Concrete Design for Thermal Effects on Nuclear Power Plant Structures Reported by ACI Committee 349 American Concrete Institute Advancing concrete knowledge Reinforced Concrete Design for Thermal Effects on Nuclear Power Plant Structures First printing June 2007 ISBN 978-0-8
2、7031-246-05 Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI. The technic
3、al committees responsible for ACI committee reports and standards strive to avoid ambiguities, omissions, and errors in these documents. In spite of these efforts, the users of ACI documents occa- sionally find information or requirements that may be subject to more than one interpretation or may be
4、 incomplete or incorrect. Users who have suggestions for the improvement of ACI documents are requested to contact ACI. Proper use of this document includes periodically checking for errata at www.concrete.org/committees/errata.asp for the most up-to-date revisions. ACI committee documents are inten
5、ded 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. Individuals who use this publication in any way assume all risk and accept total respon
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10、subscription, or reprint and may be obtained by contacting ACI. Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP). American Concrete Institute 38800 Country Club Drive Farmington Hills, MI 48331 U.S.A. Phone:248-848-3700 Fax:
11、248-848-3701 www.concrete.org ACI 349.1R-07 supersedes ACI 349.1R-91 and was adopted and published May 2007. Copyright 2007, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or
12、by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. 349.1R-1 ACI Committee Reports, Guides, Standard Practices,
13、 and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. 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 th
14、e application of the material it contains. The American Concrete Institute disclaims any and all responsibility 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
15、 this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. Reinforced Concrete Design for Thermal Effects on Nuclear Power Plant Structures Reported by ACI Committee 349 ACI 34
16、9.1R-07 This report presents a design-oriented approach for considering thermal effect on reinforced concrete structures. Although the approach is intended to conform to the general provisions of Appendix E of ACI 349, it is not restricted to nuclear power plant structures. The general behavior of s
17、tructures under thermal effects is discussed together with the significant issues to consider in reinforcement design. Two types of structuresframes and axisymmetric shellsare addressed. For frame structures, a rationale is described for determining the extent of component cracking that can be assum
18、ed for purposes of obtaining the cracked structure thermal forces and moments. Stiffness coefficients and carryover factors are presented in graph- ical form as a function of the extent of component cracking along its length and the reinforcement ratio. Fixed-end thermal moments for cracked compo- n
19、ents are expressed in terms of these factors for: 1) a temperature gradient across the depth of the component; and 2) end displacements due to a uniform temperature change along the axes of adjacent components. For the axisymmetric shells, normalized cracked section thermal moments are presented in
20、graphical form. These moments are normalized with respect to the cross-sectional dimensions and the temperature gradient across the section. The normalized moments are presented as a function of the internal axial forces and moments acting on the section and the reinforcement ratio. Use of the graph
21、ical information is illustrated by examples. Keywords: cracking (fracturing); frames; nuclear power plants; shells; structural analysis; structural design; temperature; thermal effect; thermal gradient; thermal properties. CONTENTS Chapter 1Introduction, p. 349.1R-2 1.1General 1.2Thermal effects and
22、 structural responses 1.3General guidelines 1.4Analysis techniques 1.5Consideration of thermal effects in analysis 1.6Stiffness and deformation effects 1.7Summary Chapter 2Notation and definitions, p. 349.1R-5 2.1Notation 2.2Definitions Chapter 3Frame structures, p. 349.1R-7 3.1Scope 3.2Section crac
23、king 3.3Component cracking 3.4Cracked component fixed-end moments, stiffness coefficients, and carryover factors 3.5Frame design example Omesh B. AbhatBranko GalunicCharles J. Hookham*Richard S. Orr* Adeola K. AdediranPartha S. Ghosal*Scott A. Jensen*Bozidar Stojadinovic Hansraj G. AsharHerman L. Gr
24、aves, IIIJagadish R. JoshiBarendra K. Talukdar Ranjit L. BandyopadhyayOrhan Gurbuz*Richard E. KlingnerDonald T. Ward Peter J. CarratoJames A. HammellNam-Ho LeeAndrew S. Whittaker Ronald A. CookGunnar A. Harstead*Dan J. Naus*Albert Y. C. Wong Rolf EligenhausenChristopher HeinzDragos A. NutaCharles A.
25、 Zalesiak* Werner A. F. Fuchs *Committee 349 members who were major contributors to the development of this report. Ronald J. Janowiak* Chair 349.1R-2ACI COMMITTEE REPORT Chapter 4Axisymmetric structures, p. 349.1R-21 4.1Scope 4.2 |e/d| 0.7 for compressive N and tensile N 4.3General e/d 4.4Design ex
26、amples Chapter 5References, p. 349.1R-32 5.1Referenced standards and reports 5.2Cited references Appendix AExamples in metric, p. 349.1R-33 A.1Frame design example from 3.5 A.2Design examples from 4.4 CHAPTER 1INTRODUCTION 1.1General ACI 349, Appendix E, provides general considerations in designing
27、reinforced concrete structures for nuclear power plants subject to thermal effects. Thermal effects are defined to be the exposure of a structure or component thereof to varying temperature at its surface or temperature gradient through its cross section; the resulting response of the exposed struct
28、ure is a function of its age and moisture content, temperature extreme(s), duration of exposure, and degree of restraint. The terms “force,” “moment,” and “stress” apply and are used in this report where a structure is restrained against thermally induced movements. Further treatment of these forces
29、, moments, and stresses are contained in this report as a function of type of structure. The Commentary to Appendix E, Section RE.1.2, of ACI 349-06 (ACI Committee 349 2006) instructs the designer to consider the following: 1. Linear thermal strain causes stress only under conditions of restraint, a
30、nd a portion of such stress may be self-relieving. Mechanisms for relief are: cracking, yielding, relaxation, creep, and other time-dependent deformations; and 2. Accident temperature transients may be of such short duration that the resulting temperature distributions and corresponding stress chang
31、es are not significant. Therefore, these temperature transients may not adversely affect the safe shutdown capacity of the plant. The Commentary to Appendix E, Section RE.3.3, of ACI 349-06 addresses three approaches that consider thermal effects in conjunction with all mechanical loads acting on th
32、e structure. One approach is to consider the structure uncracked under the mechanical loads and cracked under the thermal effects. The results of two such analyses are then combined. The Commentary to Appendix E also contains a method of treating temperature distributions across a cracked section. I
33、n this method, an equivalent linear temperature distribution is obtained from the temperature distribution, which can generally be nonlinear. The linear temperature distribution is then separated into a pure gradient T and into the difference between the mean and base (stress-free) temperatures Tm T
34、b. This report discusses approaches for making an assessment of thermal effects that are consistent with the aforementioned provisions. The goal is to present a designer-oriented approach for determining the reduced thermal moments that result from cracking of the concrete structure. Thermal effects
35、 should be considered in design for serviceability. The report discusses conditions under which it can be shown that the thermal effects do not adversely affect the safe shutdown capacity of the plant. Behavior and general guidance is addressed in Chapter 1. Chapter 2 addresses notation and definiti
36、ons. Chapter 3 addresses frame structures, and Chapter 4 deals with axisymmetric structures. For frame structures, general criteria are given in Sections 3.2 (Section cracking) and 3.3 (Component cracking). The criteria are then formulated for the moment distribution method of structural analysis in
37、 Section 3.4. Cracked component fixed- end moments, stiffness coefficients, and carryover factors are derived and presented in graphical form. For axisymmetric structures, an approach is described for regions away from discontinuities, and graphs of cracked section thermal moments are presented. Thi
38、s report is intended to propose simplifications that may be used for structural assessments. It will permit exclusion of thermal cases with small effect and a reduction of thermal effects for a large class of thermal cases without resorting to sophisticated and complex solutions (Appendix E, 349-06)
39、. Also, as a result of the report discussion, the design examples, and graphical presentation of cracked section thermal moments, it is hoped that a designer will better understand how thermal effects are influenced by the presence of other loads and the resulting concrete response, primarily in the
40、 form of cracking, although reinforcement yielding, concrete creep, nonlinear concrete stress-strain, and shrinkage are also very significant in mitigating thermal effects in concrete structures. 1.2Thermal effects and structural responses Thermal effects cause expansion or contraction of the compon
41、ents in a structural system. If the components are restrained, which is usually the case, stresses are induced. It is sufficient to note that there are three types of thermal effects: 1. Bulk temperature change. In this case, the entire structural component (or segments of the component) is subject
42、to a uniform temperature change; 2. Thermal gradient. A temperature crossfall or thermal gradient is caused by different thermal conditions on two faces of a structure, such as two sides of a wall or the top and bottom of a beam; and 3. Local thermal exposure. Elevated temperature at a local surface
43、 caused by an external source such as operating equipment or piping or an abnormal event such as a fire. Thermal effects will result in different states of stress and strain in structural components as a function of restraints. The analysis for thermal effects must distinguish between different type
44、s of thermal effects and properly characterize the structural response accordingly (for example, the degree of fixity of end and boundary restraints, component stiffness, influence of cracking, and concrete and reinforcing steel strain). Thermal effects can arise from many sources including, but not
45、 limited to, process fluid transport; proximity to hot gasses, steam, or water passage (for example, reactor vessel or steam piping from reactor building to turbine); fire; or gradients formed when opposing faces of a structure are DESIGN FOR THERMAL EFFECTS ON NUCLEAR POWER PLANT STRUCTURES349.1R-3
46、 exposed to differing temperatures (for example, spent fuel pool) or cyclic gradients from plant startup and shutdown. Temperature change is manifested under one or more of the following transfer mechanisms: 1. Radiation. The electromagnetic transfer of heat from a higher temperature source to a low
47、er temperature surface of the concrete structure, such as from a radiator heating a room and the surrounding wall and floor structures; 2. Convection. The transfer of heat usually by the movement of a liquid or gas across a surface, such as from environmental temperature changes in the air next to a
48、 concrete structure; and 3. Conduction. The transfer of heat through a solid, such as from a steam pipeline into the surrounding concrete at a penetration. There are many instances where all three mechanisms are present, such as in the case of a fire acting on a structure. Radiation and convection f
49、rom the flame itself transfers heat to the impinged structure. The surface of the flame radiates heat, which is absorbed by the concrete and reinforcing steel; finally, heat is transferred away from the flame-impinged area by means of conduction through the structure. The structure will also lose heat by means of convection and radiation. Response of a structure to thermal effects depends on the nature of the temperature distribution, end constraints, material properties, and mechanical loads. A proper thermal stress analysis must take these parameters
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