NACE-01102-2002.pdf
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1、Item No. 24217 NACE International Publication 01102 This Technical Committee Report has been prepared by NACE International Task Group 046*on Cathodic Protection of Prestressed Concrete Elements. State-of-the-Art Report: Criteria for Cathodic Protection of Prestressed Concrete Structures February 20
2、02, NACE International This NACE International technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing, purchasing, or using products
3、, processes, or procedures not included in this report. Nothing contained in this NACE International report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemn
4、ifying or protecting anyone against liability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictab
5、le circumstances may negate the usefulness of this report in specific instances. NACE International assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE International report are responsible for reviewing appropriate health, safety, environmental
6、, and regulatory documents and for determining their applicability in relation to this report prior to its use. This NACE International report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operati
7、ons detailed or referred to within this report. Users of this NACE International report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any exist
8、ing applicable regulatory requirements prior to the use of this report. CAUTIONARY NOTICE:The user is cautioned to obtain the latest edition of this report.NACE International reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice.NACE reports are aut
9、omatically withdrawn if more than 10 years old.Purchasers of NACE International reports may receive current information on all NACE International publications by contacting the NACE International Membership Services Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1281228-62
10、00). Foreword This NACE International state-of-the-art report is intended for use by engineers when evaluating criteria whereby pre- stressedconcretestructuresandmemberscanbe protected from corrosion by means of cathodic protection (CP). Throughout this report reference is made to pertinent, availab
11、le standards. Of particular relevance are NACE Standards RP0187,1RP0290,2and RP0390.3Under certain circumstances, the CP system can either become a structural element or significantly affect the serviceability or structural performance of the prestressed concrete element. Therefore, a review of such
12、 impact from the CP system is typically made by a registered structural engineer. This technical committee report was prepared by Task Group (TG) 046 on Cathodic Protection of Prestressed Concrete Elements.This TG is composed of corrosion researchers, corrosion engineers, corrosion consultants, arch
13、itects, structure owners, and representatives of both industry and government.TG 046 is administered by Specific Technology Group (STG) 01 on Concrete and Rebar. It is also sponsored by STG 05 on Cathodic/Anodic Protection.This technical committee report is issued by NACE International under the aus
14、pices of STG 01. _ *Chairman William H. Hartt, Florida Atlantic University, Dania Beach, FL. Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 05/16/2007 00:57:00 MDTNo reproduction or networking permitted without
15、 license from IHS -,-,- NACE International 2 Introduction Types and Principles of Prestressed Concrete Prestressed concrete has evolved during the past four-plus decades to the point that it is now widely employed for transportation structures, buildings, pipelines, and other applications because of
16、 its technical viability and economic competitiveness.While concrete per se normally exhibits acceptable compressive strength, it is relatively weak in ten- sion. Therefore, embedded steel is added to accommodate tensile stresses.For structural applications, concrete is either reinforced or prestres
17、sed (or a combination of the two). For the former, bars are positioned in the formwork; and the concrete is poured and sets such that, neglecting dead weight and service loadings, no stresses are imparted by either component (steel or concrete) to the other. The principle of prestressed concrete is
18、based on tensioning of the steel in such a manner that it ultimately places the concrete in a state of residual compression. Consequently, service tensile loadings on the concrete, up to a certain level, act to reduce this compression; and tensile stresses are either less than would otherwise be the
19、 case or are avoided altogether. A basic introductory discussion of the two types of prestressed concrete, pretensioned and post- tensioned, is provided in this Introduction.For more detailed information, a standard text in the field can be consulted.4 Types and properties of prestressing steel.Impo
20、sition of adequate residual compression to a concrete member via prestressing steel uses steel of high strength, because its cross-section is generally small compared with that of the concrete and the net force in each component (steel and concrete) balances. The specification for prestressing steel
21、 strand is provided by ASTM(1)A 416.5Currently, most pre- stressing is in the form of spiral, seven-wire strand that is designated as either Grade 250 or Grade 270, in which the number refers to minimum ultimate strength in kilopounds per square inch (ksi) units (1 ksi = 1,000 psi 6.895 MPa). Histor
22、ically, bar as well as strand has been employed. Prestressing for concrete pipe is in the form of wire and is addressed by another standard (ASTM A 6486).In either case (strand or wire), strengthening is achieved by a carbon concentration near the eutectoid composition (0.77 w%) combined with cold d
23、rawing. Heat-treated (quenched and tempered) steel is not used because of its greater suscep- tibility to brittle fracture and environmental cracking. In the past, however, quenched and tempered material has been used in some countries.Otherwise, the above standards primarily address dimensions and
24、strength, with the means by which the requisite strength is achieved being left to the producer.Steel composition is typically considered to be important, because this influences the strengthening that is derived from cold drawing. Either plain carbon or micro- alloyed steel, with small amounts of e
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