ACI-440.2R-2008.pdf
ACI 440.2R-08 Reported by ACI Committee 440 Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures First Printing July 2008 ISBN 978-0-87031-285-4 American Concrete Institute ® Advancing concrete knowledge 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 technical 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 occasionally find information or requirements that may be subject to more than one interpretation or may be incomplete or incorrect. 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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:248-848-3701 www.concrete.org ACI 440.2R-08 supersedes ACI 440.2R-02 and was adopted and published July 2008. Copyright © 2008, 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 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. 440.2R-1 ACI Committee Reports, Guides, Standard Practices, 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 the 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 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. Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures Fiber-reinforced polymer (FRP) systems for strengthening concrete structures are an alternative to traditional strengthening techniques, such as steel plate bonding, section enlargement, and external post-tensioning. FRP strengthening systems use FRP composite materials as supplemental externally bonded reinforcement. FRP systems offer advantages over traditional strengthening techniques: they are lightweight, relatively easy to install, and are noncorrosive. Due to the characteristics of FRP materials as well as the behavior of members strengthened with FRP, specific guidance on the use of these systems is needed. This document offers general infor- mation on the history and use of FRP strengthening systems; a description of the unique material properties of FRP; and committee recommendations on the engineering, construction, and inspection of FRP systems used to strengthen concrete structures. The proposed guidelines are based on the knowledge gained from experimental research, analytical work, and field applications of FRP systems used to strengthen concrete structures. Keywords: aramid fibers; bridges; buildings; carbon fibers; concrete; corrosion; crack widths; cracking; cyclic loading; deflection; development length; earthquake-resistant; fatigue; fiber-reinforced polymers; flexure; shear; stress; structural analysis; structural design; torsion. CONTENTS PART 1GENERAL Chapter 1Introduction and scope, p. 440.2R-3 1.1Introduction Tarek Alkhrdaji*Russell GentryJames G. KorffAndrea Prota Charles E. BakisJanos GergelyMichael W. LeeHayder A. Rasheed Lawrence C. BankWilliam J. GoldMaria Lopez de MurphySami H. Rizkalla Abdeldjelil BelarbiNabil F. GraceIbrahim M. MahfouzMorris Schupack Brahim BenmokraneMark F. GreenOrange S. MarshallRajan Sen Luke A. BisbyZareh B. GregorianAmir MirmiranKhaled A. Soudki* Gregg J. BlaszakDoug D. GremelAyman S. MosallamSamuel A. Steere, III Timothy E. BradberryShawn P. GrossJohn J. MyersGamil S. Tadros Gordon L. Brown, Jr.H. R. Trey Hamilton, IIIAntonio NanniJay Thomas Vicki L. BrownIssam E. HarikKenneth NealeHoussam A. Toutanji Raafat El-HachaKent A. HarriesJohn P. NewhookJ. Gustavo Tumialan Garth J. FallisMark P. HendersonAyman M. OkeilMilan Vatovec Amir Z. FamBohdan N. HoreczkoCarlos E. OspinaStephanie Walkup Edward R. FyfeVistasp M. KarbhariMax L. PorterDavid White John P. Busel Chair Carol K. Shield Secretary *Co-chairs of the subcommittee that prepared this document. The Committee also thanks Associate Members Joaquim Barros, Hakim Bouadi, Nestore Galati, Kenneth Neale, Owen Rosenboom, Baolin Wan, in addition to Tom Harmon, Renata Kotznia, Silvia Rocca, and Subu Subramanien for their contributions. Reported by ACI Committee 440 ACI 440.2R-08 440.2R-2ACI COMMITTEE REPORT 1.2Scope and limitations 1.3Applications and use 1.4Use of FRP systems Chapter 2Notation and definitions, p. 440.2R-5 2.1Notation 2.2Definitions and acronyms Chapter 3Background information, p. 440.2R-10 3.1Historical development 3.2Commercially available externally bonded FRP systems PART 2MATERIALS Chapter 4Constituent materials and properties, p. 440.2R-11 4.1Constituent materials 4.2Physical properties 4.3Mechanical properties 4.4Time-dependent behavior 4.5Durability 4.6FRP systems qualification PART 3RECOMMENDED CONSTRUCTION REQUIREMENTS Chapter 5Shipping, storage, and handling, p. 440.2R-15 5.1Shipping 5.2Storage 5.3Handling Chapter 6Installation, p. 440.2R-16 6.1Contractor competency 6.2Temperature, humidity, and moisture considerations 6.3Equipment 6.4Substrate repair and surface preparation 6.5Mixing of resins 6.6Application of FRP systems 6.7Alignment of FRP materials 6.8Multiple plies and lap splices 6.9Curing of resins 6.10Temporary protection Chapter 7Inspection, evaluation, and acceptance, p. 440.2R-19 7.1Inspection 7.2Evaluation and acceptance Chapter 8Maintenance and repair, p. 440.2R-21 8.1General 8.2Inspection and assessment 8.3Repair of strengthening system 8.4Repair of surface coating PART 4DESIGN RECOMMENDATIONS Chapter 9General design considerations, p. 440.2R-21 9.1Design philosophy 9.2Strengthening limits 9.3Selection of FRP systems 9.4Design material properties Chapter 10Flexural strengthening, p. 440.2R-24 10.1Nominal strength 10.2Reinforced concrete members 10.3Prestressed concrete members Chapter 11Shear strengthening, p. 440.2R-32 11.1General considerations 11.2Wrapping schemes 11.3Nominal shear strength 11.4FRP contribution to shear strength Chapter 12Strengthening of members subjected to axial force or combined axial and bending forces, p. 440.2R-34 12.1Pure axial compression 12.2Combined axial compression and bending 12.3Ductility enhancement 12.4Pure axial tension Chapter 13FRP reinforcement details, p. 440.2R-37 13.1Bond and delamination 13.2Detailing of laps and splices 13.3Bond of near-surface-mounted systems Chapter 14Drawings, specifications, and submittals, p. 440.2R-40 14.1Engineering requirements 14.2Drawings and specifications 14.3Submittals PART 5DESIGN EXAMPLES Chapter 15Design examples, p. 440.2R-41 15.1Calculation of FRP system tensile properties 15.2Comparison of FRP systems tensile properties 15.3Flexural strengthening of an interior reinforced concrete beam with FRP laminates 15.4Flexural strengthening of an interior reinforced concrete beam with NSM FRP bars 15.5Flexural strengthening of an interior prestressed concrete beam with FRP laminates 15.6Shear strengthening of an interior T-beam 15.7Shear strengthening of an exterior column 15.8Strengthening of a noncircular concrete column for axial load increase 15.9Strengthening of a noncircular concrete column for increase in axial and bending forces Chapter 16References, p. 440.2R-66 16.1Referenced standards and reports 16.2Cited references APPENDIXES Appendix AMaterial properties of carbon, glass, and aramid fibers, p. 440.2R-72 Appendix BSummary of standard test methods, p. 440.2R-73 DESIGN AND CONSTRUCTION OF EXTERNALLY BONDED FRP SYSTEMS440.2R-3 Appendix CAreas of future research, p. 440.2R-74 Appendix DMethodology for computation of simplified P-M interaction diagram for noncircular columns, p. 440.2R-75 PART 1GENERAL CHAPTER 1INTRODUCTION AND SCOPE 1.1Introduction The strengthening or retrofitting of existing concrete structures to resist higher design loads, correct strength loss due to deterioration, correct design or construction deficiencies, or increase ductility has traditionally been accomplished using conventional materials and construction techniques. Externally bonded steel plates, steel or concrete jackets, and external post-tensioning are just some of the many traditional techniques available. Composite materials made of fibers in a polymeric resin, also known as fiber-reinforced polymers (FRPs), have emerged as an alternative to traditional materials for repair and rehabilitation. For the purposes of this document, an FRP system is defined as the fibers and resins used to create the composite laminate, all applicable resins used to bond it to the concrete substrate, and all applied coatings used to protect the constituent materials. Coatings used exclusively for aesthetic reasons are not considered part of an FRP system. FRP materials are lightweight, noncorrosive, and exhibit high tensile strength. These materials are readily available in several forms, ranging from factory-made laminates to dry fiber sheets that can be wrapped to conform to the geometry of a structure before adding the polymer resin. The relatively thin profiles of cured FRP systems are often desirable in applications where aesthetics or access is a concern. The growing interest in FRP systems for strengthening and retrofitting can be attributed to many factors. Although the fibers and resins used in FRP systems are relatively expensive compared with traditional strengthening materials such as concrete and steel, labor and equipment costs to install FRP systems are often lower (Nanni 1999). FRP systems can also be used in areas with limited access where traditional techniques would be difficult to implement. The basis for this document is the knowledge gained from a comprehensive review of experimental research, analytical work, and field applications of FRP strengthening systems. Areas where further research is needed are highlighted in this document and compiled in Appendix C. 1.2Scope and limitations This document provides guidance for the selection, design, and installation of FRP systems for externally strengthening concrete structures. Information on material properties, design, installation, quality control, and maintenance of FRP systems used as external reinforcement is presented. This information can be used to select an FRP system for increasing the strength and stiffness of reinforced concrete beams or the ductility of columns and other applications. A significant body of research serves as the basis for this document. This research, conducted over the past 25 years, includes analytical studies, experimental work, and monitored field applications of FRP strengthening systems. Based on the available research, the design procedures outlined in this document are considered to be conservative. It is important to specifically point out the areas of the document that still require research. The durability and long-term performance of FRP materials has been the subject of much research; however, this research remains ongoing. The design guidelines in this document do account for environmental degradation and long-term durability by suggesting reduction factors for various environments. Long-term fatigue and creep are also addressed by stress limitations indicated in this document. These factors and limitations are considered conservative. As more research becomes available, however, these factors will be modified, and the specific environmental conditions and loading conditions to which they should apply will be better defined. Additionally, the coupling effect of environmental conditions and loading conditions still requires further study. Caution is advised in applications where the FRP system is subjected simultaneously to extreme environmental and stress conditions. The factors associated with the long-term durability of the FRP system may also affect the tensile modulus of elasticity of the material used for design. Many issues regarding bond of the FRP system to th
