https://doi.org/10.14311/APP.2022.33.0039 Acta Polytechnica CTU Proceedings 33:39–44, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague CONFORMITY ASSESSMENT MODEL FOR MECHANICAL COUPLING DEVICES AND ANCHORS FOR REINFORCING STEEL FOR USE IN CONCRETE STRUCTURE Lee Brankley, Ayhan Turgul, Lyn Morgan, Ladin Camci∗ CARES, Pembroke House, 21 Pembroke Road, Sevenoaks, Kent TN13 1XR, United Kingdom ∗ corresponding author: ladincamci@ukcares.com Abstract. The use of mechanical coupling devices and anchors for reinforcing steel for use in concrete structures can simplify the design and construction of reinforced concrete and reduce the amount of reinforcement required. Technical Approvals of these products by suitably qualified organisations are acceptable under Building Regulations and by major specifiers as the appropriate way of assessing non-standard or new and innovative products. Specifiers, manufacturers, traders, and customers in- creasingly demand certainty in the quality management of mechanical coupling devices and anchors entering the supply chain. The supply chain is extremely complex. The weak traceability systems and pressure on the supply chain to reduce cost have created the environment where risks increase. This unique and comprehensive model describes the technical and assessment requirements for the confor- mity of mechanical coupling devices and anchors. It covers all stages in the supply chain from the production, assembly, product performance and evaluation of mechanical properties including tensile strength, ductility, permanent elongation (slip), cyclic loading performance and fatigue performance. The essential elements of the quality management system combined with additional requirements on process control, product testing and robust installation methodology are essential and agreed by all relevant sectors of industry. Keywords: Certification, mechanical rebar anchors, mechanical rebar couplers, mechanical rebar splicing systems, product conformity. 1. Introduction The CARES Technical Approval Scheme for Couplers and Anchors provides a comprehensive assessment process, ensuring complete product traceability to the construction site. A key part of assessment process is the development of a Technical Approval report which not only indicates the performance character- istics and conformity of the product, but also ensures that correct assembly to the rebar is undertaken with robust installation procedures contained within each report. The CARES Technical Approval Scheme predomi- nantly covers couplers for use with BS 4449 [1] rein- forcing steel. CARES with its global presence have recognised the need for more global approvals and have recently introduced a scheme which not only supports CARES approved rebar to BS 4449 [1], but also rebar to EN 10080 [2], ASTM A615/A615M [3], ASTM A706/A706M [3], ISO 6935-2 [4] and SS 560 [5]. The CARES Technical Approval certification scheme for the supply and installation of Couplers and Anchors has been developed in conjunction with the CARES Technical Committee, made up of various interested parties including leading Structural Engi- neers, specifiers, and coupler producers. The Schemes are based on the demonstration of the continuing operation of the quality management system consistent with ISO 9001 [6], the appropriate Quality and Operations Assessment Schedule [7] and the ability to manufacture, supply and / or install material or product complying with BS 8597 [8], Sel- lafield Engineering Standard [9], Highways England Manual [10] or more recently, ISO 15835 [11]. At the initial approval stage, all quality affecting manufacturing processes are audited whether pro- duced internally or outsourced via approved sub- contract suppliers. Once approved, all CARES ap- proved coupler / anchor manufacturers must ensure any design, material specification, supply chain or in- stallation instruction changes are vetted by CARES to ensure any necessary testing is further carried out to ensure product conformity is maintained prior to the change. The CARES Coupler Technical approval scheme is further supported both downstream and upstream by the CARES Steel Certification scheme where re- inforcing bar fabricators must also be CARES ap- proved for installation of couplers on the reinforcing steel (CARES SRC08 Scheme). 2. Objective The objective of the Technical Approval Scheme is to give confidence to the purchaser that the construction 39 https://doi.org/10.14311/APP.2022.33.0039 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en L. Brankley, A. Turgul, L. Morgan, L. Camci Acta Polytechnica CTU Proceedings Schedules No. Description TA1-A Technical Approval of Couplers for Reinforcing Steel for use in Structures and Structuralelements Designed in accordance with the Fatigue Requirements of Structural Eurocodes TA1-B Technical Approval of Couplers for Reinforcing Steel and Reinforcement Anchors for BS 8110 [12] and EN 1992-1-1 [13] Applications for Static Loading in Tension or Tension and Compression. TA1-C Technical Approval of Tension Couplers for Reinforcing Steel for Sellafield EngineeringStandard [9] Applications TA1-F Technical Approval of Couplers for high cycle fatigue and low cycle loading and static loadingapplications in tension. SRC08 Quality and Operations Assessment Schedule [7] for the application of mechanical couplersto reinforcing steel Table 1. Quality and Operations Assessment Schedules [7]. product complies with the appropriate specification without the need to undertake separate verification. Additionally, it provides confidence in both traceabil- ity and correct installation methodology. This in- volves the application of quality assurance principles to assess the supplier’s and supply chain quality sys- tems and, as appropriate, product testing to ensure conformity with the requirements contained in each Scheme at each part of the supply chain. 3. Assessment and certification system 3.1. Principles The assessment and certification system employed in the Scheme has been developed around the following common principles: • The Scheme is concerned with ensuring that the construction product complies with the relevant product Standards and / or client specifications. • The responsibility for complying with the Stan- dards rests absolutely with the approved Firm. • The means of providing assurance of consistent compliance with the Standards or Specifications shall be the formal management system for qual- ity, including process control, which the approved Firm is required to have documented and to be op- erating to the satisfaction of CARES. This system is subject to ongoing audits at periodic intervals. • A key method of verifying compliance of the prod- uct is by the independent assessment and surveil- lance of the approved Firms management system for quality, including witness testing of the prod- uct as appropriate • Additionally, independent inspection and testing of the product is undertaken by testing laboratories approved by CARES. • Long Term Quality level reviews and quality com- plaints are a key feature of the ongoing surveillance programme. 3.2. Quality and Operations Assessment (Technical Assessment) Schedules The Schemes Quality and Operations Assessment Schedules [7] for couplers and anchors are shown in Table 1. 3.3. Assessment The assessment consists of: • Full assessment in accordance with the relevant Quality and Operations Assessment Schedule [7]. • The manufacturing process route integrity, includ- ing records, resources, training, contract review, product requirements, manufacturing controls and interfaces. • Review of installation methodology and product di- mensional conformance. • Product conformity assessment by sampling in ac- cordance with the relevant Quality and Operations Assessment Schedule [7]. • Preparation and issue of the CARES Technical Ap- proval Report for the couplers / anchors assessed. 3.4. Applicant The applicant is required to have and be able to demonstrate: • The ability and resources required to produce the coupler / anchor to the relevant Standard(s) and / or specifications consistently. • A quality management system which complies with the requirements of ISO 9001 [6], and the relevant Quality and Operations Assessment Schedule [7]. The system shall be described formally in the sup- plier’s Quality Manual. • Adequate control of approved suppliers and incom- ing product. • The ability of the coupler manufacturer to control its supplier is essential in the case of approval of cementitious grouted couplers, where the grout has 40 vol. 33/2022 Model Assessment of Reinforcing Steel in Concrete Structure tight performance requirements as part of the latest Coupler Technical Approval scheme TA1-F. • Robust installation methodology which is readily transferrable to downstream fabricators or site in- stallers. 3.5. Certification A recommendation for approval is produced when the manufacturing procedures and product confor- mity have been assessed and the Scheme criteria have been satisfied and all reported deficiencies have been addressed to the satisfaction of CARES. A key part of this recommendation process is the preparation and subsequent approval of the coupler / anchor Technical Approval report. Copies of all the issued Technical Approval reports are freely and readily available to download from the CARES web- site (www.ukcares.com). The Certificate of Approval is valid for one year with renewal subject to continuing satisfactory per- formance of the construction product. Firms granted Certificates of Approval are required to reproduce the CARES Logo, and the Certificate of Approval num- ber on all relevant documentation. 3.6. Ongoing Surveillance The assessment and certification system employed in the Scheme has been developed around the following common principles: Firms granted Certificates of Approval are required to undergo surveillance audits by CARES twice per annum, to ensure continued compliance with the re- quired Scheme and Product Standard. Samples of the construction product may be witnessed tested at the manufacturer in addition to the requirement to test "mirror" samples at an independent laboratory approved by CARES. All Technical approval schemes require that key variables of the original tested component remain un- changed. The following variables as applicable to the type of approved coupler shall not be changed without the prior agreement and subsequent assessment by CARES: a) Coupler component material or grade or process route of the raw material used to manufacture the coupler b)Cross-sectional area of the splice sleeve c) Bar engagement length d)Reinforcing bar profile (rib pattern), grade or spec- ification e) Bar locking device f) Thread geometry g) Torque h)Swaging pressure i) Die geometry j) Production process or production location k) Approved grout supplier and / or change in grout specification or properties (in the case of cementi- tious grouted coupler) l) Installation instructions A key condition of the CARES Technical approval schemes are that any subsequent changes to the above must be reviewed by CARES prior to the implemen- tation of the change, thus ensuring that any extra testing is undertaken to ensure continued product conformity. Failure to do so will usually lead to the removal of the Technical Approval and the CARES approval certificate. New suppliers deemed critical for the processed part will be assessed by CARES before production can commence. All sub-suppliers are visited at least once every three years as part of the ongoing surveil- lance Installation instructions are validated at each surveillance visit, by means of witness sampling of the coupler and application to the reinforcing bar. 3.7. Key attributes of the approved coupler / anchor The approved coupler / anchor attributes include a) Tensile properties, ensuring the connected reinforc- ing steel properties are not compromised b)Slip < 0.10 mm (permanent elongation after un- loading from 60% / 65% of the characteristic yield strength of the reinforcing steel). This is key re- quirement in all the CARES Coupler Schemes not only at the initial assessment but also ongoing fac- tory production control surveillances. Control on slip is essential to ensure adequate concrete crack control. c) Mode of failure, within or outside the coupler as- sembly. d)Performance in low cycle / high cycle fatigue ac- cording to each CARES scheme appropriate to the coupler final application, whether Highway bridges, critical installations such as Nuclear or areas of po- tential seismic activity. e) Designed to allow consistent and robust installa- tion methods readily repeatable whether at fabri- cators or on site 3.8. Methodology of conformity assessment and ongoing surveillance for the coupler / anchor approval Key requirements of the CARES assessment and surveillance methodologies are: a) Use of assessors who have a background in the Steel production and / or construction industry is critical. These assessors will also have a thor- ough knowledge of principals of ISO9001, with clear 41 www.ukcares.com L. Brankley, A. Turgul, L. Morgan, L. Camci Acta Polytechnica CTU Proceedings attention to Factory Production control (FPC), maintenance of traceability, construction product properties and installation methodology. b)The manufacturing site visits, including visiting of any key sub-contract operations are agreed with the client in advance and an audit itinerary issued to ensure full understanding of the requirements. c) A key part of each audit of the client and any sub- contractors is to establish confidence in their FPC and associated procedures, purchase control and specifications, incoming inspection of goods and fi- nal product inspection and release. d)Management of change is facilitated using Sched- ules of operations which are required to be pro- duced by each approved client and required to be updated regularly to detail any changes to the agreed manufacturing process route, critical sub- contractors, purchasing specifications and product drawings. Also included are the issue status of op- erational procedures for any rebar end preparation / threading machines leased to CARES approved fabricators. These schedules are reviewed during audits to ensure there an adequate management of change record, thus ensuring confidence in the maintenance of the product properties. e) Sampling of the assembled product is a key feature at each audit whether at the manufacturer or fab- ricator following the agreed installation procedure. These are subsequently tested at independent lab- oratories which are approved by CARES f) Continued approval and certification is only al- lowed following successful auditing and product testing. Any areas for improvement are followed up the issue of non-conformances which require the client to undertake a root cause analysis, immedi- ate remediation, and corrective actions. 4. Identification and traceability system CARES certification provides full traceability from the molten steel to the construction site by addressing all stages of production, delivery, and receipt. Once installed and cast into concrete within the structure, construction components cannot be easily removed even if there is a product failure or a manu- facturing deficiency. There is no ’product recall’ when things go wrong with steel in the structure of a prized project. Its performance must be assured from the outset. CARES have embraced the digitalisation era by developing and promoting its CARES Cloud. This CARES digital platform plans to cover all stages in the supply chain from receipt of raw materials, the manufacture and processing of steel products through to delivery to the end user. It delivers product test results and sustainability credentials that are trace- able across the whole supply chain ensuring that re- bar is effectively tested, marketed, and traced. Criti- cally, in the latter stages of this development it could also confirm where these products are installed in the structure. 5. Construction product supply chain - CARES approach The supply chain is designed to give confidence to the purchasers and the Technical approval schemes are supported by the Steel Schemes as shown in Figure 1. For a product to be CARES approved, all the sup- ply chain must be approved, whether it is the steel- maker, roller, steel trader or fabricator, there shall be no break in this link. Coupler installation is rigorously reviewed during surveillance at approved fabricators as part of the CARES Steel Scheme SRC08, ensuring agreed instal- lation procedures are maintained in line with those detailed in the appropriate Technical Approval re- port. Witnessed coupled rebar is taken for subse- quent independent testing at an agreed rate over the surveillance period. 6. Assessment models and specification • CARES TA1-A Quality and Operations Schedule for the Technical Approval of Couplers for Rein- forcing Steel for use in Structures and Structural elements Designed in accordance with the Fatigue Requirements of Structural Eurocodes: This scheme is based on the require- ments of the Highways England [10] specification for Highways structures, with continual product as- sessment by independent testing and LTQL. Test- ing includes both tensile and high cycle fatigue test- ing. • CARES TA1-B Quality and Operations Schedule for the Technical Approval of Couplers for Rein- forcing Steel and Reinforcement Anchors for Static Loading in Tension or Tension and Compression: This scheme is based on the requirements of BS 8597 [8], with continual prod- uct assessment by independent testing and LTQL. Testing includes both tensile and optional compres- sion testing. • CARES TA1-C Quality and Operations Schedule for the Technical Approval of Tension or Tension- Compression Couplers for Reinforcing Steel and Reinforcement Anchors for Nuclear Ap- plications based on Sel lafield Engineering Standard [9]: This scheme is based on the re- quirements of the Sellafield Engineering Standard 42 vol. 33/2022 Model Assessment of Reinforcing Steel in Concrete Structure Figure 1. Concept of ’extended’ product responsibility applied to reinforcing steel. [9], with continual product assessment by indepen- dent testing. Testing includes both tensile, includ- ing cold soak tensile testing, low cycle, and high cycle fatigue testing. • CARES TA1-F Quality and Operations Schedule for the Technical Approval of Couplers for high cy- cle fatigue and low cycle loading and static loading applications in tension: This scheme is based on the requirements of ISO 15835 [11] with enhancements. Continual product assessment in line with the standard by independent testing. Testing includes tensile, optional low cycle and high cycle fatigue testing. This is the first CARES scheme to include a cementitious grouted coupler, hence evidence of conformance and product perfor- mance of the specified grout is a key part of this scheme. This built on CARES experience of using grout on site for bonded tendons in Post Tensioning installations. 7. Conclusion CARES is an independent, not-for-profit certification body. The certification scheme for both the Steel supply chain and installation of couplers in its re- quirements, providing for good management control, consistent product and technical conformity, indus- try developed disciplines, rules and standards and auditing by industry professionals with many years- experiences in the appropriate industry. CARES reduce the risk of using Construction prod- ucts which do not meet the Specification require- ments, and to enable feedback and corrective action in case problems arise. Major construction clients, designers, and contractors worldwide, recognise and even specify CARES and its certification scheme to gain assurance of consistent product quality and tech- nical competence. CARES maintain its Construction products devel- opment by attendance at the European Organisation of Technical Approval (EOTA) meetings and actively participate in various ISO, EN and BS standard meet- ings. CARES Schemes are prepared in collaboration with the relevant Technical Committees of inter- ested parties which include senior structural engi- neers, specifiers, and producers. References [1] BS 4449:2005+A3:2016: Steel for the reinforcement of concrete Bar, coil and decoiled product, European Standards, 2016. [2] EN 10080:2005 Steel for the reinforcement of concrete - Weldable reinforcing steel - General, 2005. [3] ASTM A615/A615M: 2018 Standard specification for Deformed and Plain Carbon Steel-Bars for Concrete Reinforcement & ASTM A706/A706M:2016 Standard specification for Deformed and Plain Low-Alloy Steel Bars for Concrete Reinforcement, 2018. [4] ISO 6935-2:2019 Steel for the reinforcement of concrete - Part 2: Ribbed bars, 2019. [5] SS 560:2016 (Singapore Standard) Specification for steel for the reinforcement of concrete - weldable reinforcing steel - Bar, coil and decoiled product, 2016. [6] ISO 9001:2015 Quality Management Systems - Requirements, 2015. [7] CARES Quality and Operations Assessment Schedules. www.ukcares.com. [8] BS 8597:2015 Steels for the reinforcement of concrete - Reinforcement couplers - Requirements and test methods, 2015. 43 www.ukcares.com L. Brankley, A. Turgul, L. Morgan, L. Camci Acta Polytechnica CTU Proceedings [9] Sellafield Engineering Standard ES_0_3110_2 Issue-4 Mechanical Splices to Reinforcement for Concrete. Part 2 - Manufacturing, Installation and Construction Requirements. https://www.ukcares.com/TAPDF/5067.pdf. [10] Highways England MHWA Amendment 2014 Manual of contract documents for highways works volume 1, series 1700, 2014. [11] ISO 15835-1:2018 Steel for the reinforcement of concrete - Reinforcement couplers for mechanical splices of bars - Requirements, ISO 15835-2:2018 Steel for the reinforcement of concrete - Reinforcement couplers for mechanical splices of bars - Test Methods & ISO 15835-3:2018 Steel for the reinforcement of concrete - Reinforcement couplers for mechanical splices of bars - Conformity assessment scheme, 2018. [12] BS 8110 Structural use of concrete (replaced by Eurocode 2), British Standard. [13] EN 1992-1-1:2004, Eurocode 2: Design of Concrete Structures - Part 1-1: General rules and rules for buildings, 1992. 44 https://www.ukcares.com/TAPDF/5067.pdf