Introduction to guidelines for ReforceTech BFRP reinforcement bars in concrete structures Issued: February 2010 DNV Technical Report 2009-0316 Qualification of Basalt Fibre Reinforced Polymer (BFRP) Bars for Application in Reinforced Concrete Structures Rev. 0, 2010-02-01 For ReforceTech AS
Foreword ReforceTech AS develops a new technology for efficient production of basalt fibre reinforced polymer (BFRP) bars for reinforcement of concrete structures. DNV was contracted to qualify this technology for reliable and safe use in load-bearing concrete structures according to DNVs procedures documented in DNV-RP-A203 and DNV-OSS-401. DNV has 1) managed technology qualification, 2) executed qualification activities in collaboration with the technology owner and others, to document with confidence the bar s performance as reinforcement in concrete structures and 3) developed Guidelines for these bars. The Guidelines are provided in this document. The ReforceTech BFRP bars are considered fit for service as reinforcement in concrete structures if produced 1) in accordance with the specification provided in Section 3.1 of DNV Technical Report 2009-0316 Qualification of Basalt Fibre Reinforced Polymer (BFRP) Bars for Application in Reinforced Concrete Structures Rev. 0 dated 2010-01-29, 2) under strict quality assurance and control in accordance with these Guidelines. BFRP bars deliveries are considered fit for service as reinforcement in concrete structures when the actual delivery has been verified to have been produced in accordance with the above. Separate verification shall be performed to ensure that concrete structures reinforced with these BFRP bars are designed, constructed and maintained in compliance with these Guidelines. Structures for service in areas with own regulations for design and construction need approval by the applicable regulatory authority. Text that applies specifically to the ReforceTech product is shown shaded and in frames and is not applicable to other products. These Guidelines shall be used together with DNV-OS-C502 Offshore Concrete Structures. All requirements of that standard apply unless expressly stated otherwise herein. If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million. In this provision Det Norske Veritas shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of Det Norske Veritas. DNV shall not be kept legally liable for not having identified failure modes or causes that has resulted in loss or damage or for not having prescribed the qualification activities necessary to avoid the loss or damage.
Introduction Refer to DNV-OS-C502 for A100 A500. Objective 107 The objective of these guidelines is to provide guidance on the design, construction and in-service inspection of concrete structures reinforced with BFRP bars instead of or in combination with steel reinforcement bars such that, when these guidelines are used in conjunction with an applicable national or international standard, a structure that is fit for service is obtained. Scope, limitations and application 202 These guidelines are applicable to design, construction and inspection of concrete structures that are covered by the object standard applied in conjunction with these guidelines. Provided that this is agreed between the parties, acceptable within the applicable jurisdiction and accepted by the responsible approval authority, these guidelines can serve as a contractual reference document between the parties and form the basis for approval (certification or classification). In case of ambiguity in interpretation of the provisions herein, the basis documented in DNV-TR-2009-0316 and the documents referenced therein should be considered. If this does not resolve the ambiguity, the issue can be resolved by a dedicated technology qualification exercise according to DNV-RP-A203. A 600 Users of the Guidelines 601 The client is understood to be the party ultimately responsible for the system as installed and its intended use in accordance with the prevailing laws, statutory rules and regulations. 602 The authorities are the national or international regulatory bodies. 603 The contractor is understood to be the party contracted by the client to perform all or part of the necessary work needed to bring the system to an installed and operable condition. 604 Subcontractors are contracted by the contractor to perform of the work needed to bring the system to an installed and operable condition. The designer is understood to be the party contracted to fulfil all or part of the activities associated with the design. Manufacturers are understood to be the party contracted to manufacture all or part of the system being responsible for its deliveries. They include the manufacturer of the bars and the party constructing the concrete structure. 605 The third party verifier is an independent neutral party that verifies the design of a structure or component.
A700 Guidelines for BFRP bars 701 These guidelines are the result of a structured technology qualification process carried out according to DNV-OSS-401 and DNV-RP-A203. The guidelines provide principles, technical requirements and guidelines for the design, construction and in-service inspection of concrete structures. Compliance of a specific structural design and construction with these guidelines implies that the structure is fit for the specified service if the QA/QC ensures that the bars used are according to specifications and that design, construction and in-service inspection meets the criteria of these guidelines. 702 All aspects of concrete structures not covered herein should be in compliance with recognized international or national standards. 703 These Guidelines are so structured as to provide particularly user-friendly application together with DNV-OS-C502 Offshore Concrete Structures. 704 Furthermore, the Guidelines address specifically how the structural design prescriptions of NS 3473, developed for steel reinforcement bars, can be modified to account for the particular properties of BFRP reinforcement bars. 705 It shall be noted that NS3473 covers only Section 6 of this Guideline; hence the provisions of Sections 1, 2, 3, 4, 5, 7 and 8 shall still apply when using NS3473 together with Appendix H as the basis for detailed design. 706 Appendix H Guidelines for design of BFRP reinforced concrete member together with NS3473 is not approved by Norsk Standard and shall be considered as recommendations only. 707 For structures other than offshore structures, the proper use of these Guidelines results in reliable structural designs if the load combinations specified in EN1990 and quoted in Sec. 5 C114 are accounted for. These Guidelines are not approved by Comité Européen de Normalisation (CEN) and such use of the Guidelines shall be considered as recommendations only. 708 In using BFRP reinforcement in reinforced concrete structures, the following advantages and disadvantages should be noted. The success in applying the material in an cost effective manner will depend on taking necessary account of these advantages and disadvantages. Advantages: Low weight. The bars has a density which is 1/4 of steel reinforcement. Concrete dimensions and weight will be less due to reduced need for concrete cover. BFRP does not corrode and can be positioned close to the surface. The size of cover is only dependent on specifying sufficient cover to transfer bond. Meshes of BFRP bars with small diameter may be placed at low cover to considerably improve the SLS performance (crackwidth) of BFRP reinforced members. As the BFRP reinforcement is not sensitive to corrosion, larger cracks may be accepted for BFRP reinforced structural members than what is acceptable for steel reinforced concrete members in cases where crackwidth control is not controlled by visual appearance. BFRP reinforcement has a higher initial tensile strength than steel reinforcement. BFRP reinforcement can be prestressed to a relative low values and still retain its prestressing level when considering losses due to its low E modulus. BFRP reinforced concrete members are more flexible than steel reinforced concrete members and may be very useful where high flexibility is important. BFRP reinforced concrete members undergo large deflections prior to failure. The failure deflection is larger than normal for steel reinforced members. Also, the deflection increase with a steadily increasing load, while steel reinforced members only experience a small load carrying increase following yield of the reinforcement.
Disadvantages: BFRP reinforcement can be used together with other steel reinforcement or steel tendons. The likely application of BFRP bars in this case is for surface reinforcement. In cases with mixed application of steel and BFRP, the critieria for crack width control and concrete cover to steel reinforcement and tendons apply. The E modulus of BFRP is much lower than steel reinforcement. This has impact on strength (position of neutral axis), shear strength (contribution from longitudinal bars and shear reinforcement), minimum reinforcement, deflection and crack widths. The material has to be applied differently than in traditional steel reinforced concrete structures to become cost effective. The BFRP material has a strength which is dependent on the time of load exposure. This is named the sustained load effect. Special load combinations with different material factors for BFRP are assigned for each load combination to account for this effect. BFRP reinforcement are relative light, but shall also be handled relatively carefully at the construction site in order not to damage the bars. The BFRP reinforcement has to follow a tight production control system and relevant properties of the BFRP has to be provided on data sheet to the designer and also as part of the construction control.
Table of Contents in the DNV guideline Foreword 5 Introduction 6 A. General 6 B. References 8 C. Definitions 9 D. Abbreviations and symbols 9 Safety Philosophy 12 D. BFRP Bars 12 Design documentation 13 E. Documentation for BFRP bars 13 Structural materials 14 B. Definitions 14 C. Material requirements 14 F. Reinforcement 20 G. Prestressing steel 21 I. Testing of materials 21 Section 5 Loads and analyses requirements 24 A. Requirements to Design 24 B. Load and Load Effects 24 C. Load Combinations and Partial Safety Factors 24 D. Structural Analyses 25 E. Topside Interphase Design 26 F. Barge Type Structures 26 Detailed design 27 A. General 27 B. Design principles 27 C. Basis for design by calculation 29 D. Bending Moment and Axial Force (ULS) 30 E. Slender structural elements 30 F. Shear forces in beams and slabs 31 G. Torsion moments in beams 32 H. General design method for structural members subjected to in-plane forces 32 I. Regions with discontinuity in geometry or loads 33 J. Shear forces in construction joints 33 K. Bond strength and Anchorage failure 33 L. Partially loaded areas 34
M. Fatigue limit state 34 N. Accidental limit states 36 O. Serviceability limit state 36 P. Design by testing 38 Q. Rules for detailing of reinforcement 38 R. Structural detailing rules 39 S. Corrosion control 41 Section 6 Construction 42 A. General 42 B. Definitions 42 C. Documentation 42 D. Quality Control Inspection, Testing and Corrective Actions 42 E. Construction Planning 42 F. Material and Material Testing 43 G. Formwork 43 H. Reinforcement and Embedded Steel 43 I. Production of Concrete and Grout 43 J. Transport, Casting, Compaction and Curing of Concrete 43 K. Completion of Prestressing Systems 44 I. Repairs 44 M. Corrosion protection 44 N. Site Records and As-Built Documentation 44 O. Precast Concrete Elements 44 P. Geometric Tolerances 44 Section 7 In-service inspection, maintenance and condition monitoring 45 A. General 45 App. A Environmental loading (Guidelines) 46 App. B Structural analyses Modelling (Guidelines) 47 App. C Structural analyses (Guidelines) 48 App. D Seismic Analyses (Guidelines) 49 App. E Use of alternative detailed design standard (Guidelines) 50 App. F Crackwidth calculations (Guidelines) 51 App. G Crackwidth calculations for BFRP REINFORCED MEMBERS (Guidelines) 52 App. H Guidelines for BFRP reinforcement bars in concrete structures for use with NS3473 55 1. Introduction 55 General 55 References 57 Definitions 58
Abbreviations and symbols 58 2. Safety Philosophy 60 BFRP Bars 60 3. Design documentation 60 Documentation for BFRP bars 60 4. Structural materials 61 Definitions 61 Material requirements 61 Reinforcement 67 Prestressing steel 67 Testing of materials 68 5. Loads and analyses requirements 70 Requirements to Design 70 Load Combinations and Partial Safety Factors 70 Partial load factors, F 70 Definition of material factors to be used in design 71 6. STRUCTURAL DESIGN 73 Basis for Design by Calculations 73 General Bending Moment and Axial Force (ULS) 75 Shear forces in beams and slabs 75 Torsion moments in beams 78 Torsion 78 General design method for structural members subjected to in-plane forces 78 Regions with discontinuity in geometry or loads 78 Shear forces in construction joints 78 Bond strength and Anchorage failure 79 Partly loaded areas 79 Fatigue limit state 80 Accidental Limit State 81 Serviceability Limit State 81 Concrete cover 85 Design by testing 86 Structural detailing rules / Minimum Reinforcement 86 7. INSPECTION OF MATERIAL AND PRODUCTS 88 8. CONSTRUCTION 88 Reinforcement and prestressing system components 88 Reinforcement 88 Prestressing using BFRP reinforcement 88
References Refer to DNV-OS-C502 for B100. References for use of BFRP bars 201 The recognised reports, codes, guidelines and standards in Table 1 are referenced in these guidelines. Table 1: Other references Reference DNV-TR-2009-0316 ACI 440.1R-06 ACI 440.3R-04 ACI 440R-07 CSA 806-02 ISO 10406-1 SINTEF Title Qualification of Basalt Fibre Reinforced Polymer (BFRP) Bars for Application in Reinforced Concrete Structures. DNV Technical Report 2009-0316. Guide for the design and construction of structural concrete reinforced with FRP bars. American Concrete Institute. February 10, 2006 Guide test methods for fiber-reinforced polymers (FRPs) for reinforcing or strengthening concrete structures. American Concrete Institute. June 28, 2004. Report on fiber-reinforced polymer (FRP) reinforcement for concrete structures. American Concrete Institute. September 2007 Design and Construction of Building Components with Fibre-Reinforced Polymers. Canadian Standards Association. November 2005 Fibre-reinforced polymer (FRP) reinforcement of concrete Test methods Part 1 FRP bars and grids. ISO, 2008-12-15 Eurocrete. Modification to NS3473 when using fiber reinforced (FRP) reinforcement, Cement and Concrete 1998-04-8. ACI 440-4R 04 Prestressing Concrete Structures with FRP Tendons. September 21, 2004 List of reports Waagaard et al. Qualification of Basalt Fibre Reinforced Polymer (BFRP) Bars for Application in Reinforced Concrete Structures. DNV Technical Report 2009-0316. Rev.0, 2010-02-01. McGeorge D et al. Tests report on large scale beams and slabs with BFRP bar reinforcement. Det Norske Veritas AS. Technical Report 2009-3141, Rev.0, 2010-01-29. McGeorge D et al. Tensile strength properties of BFRP bars in the long and short term, DNV Technical Report 2009-3140, Rev.0, 2010-01-17. McGeorge D et al. Elongation properties of BFRP bars: E-modulus, creep and thermal expansion, DNV Technical Report 2009-3142, Rev.0, 2010-01-17 McGeorge D et al. Bond and bend strength of BFRP bars, DNV Technical Report 2009-3139, Rev.0, 2010-01-18.