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EC2 punching shear specification?

EC2 punching shear specification?

The 'quality' answer is CARES approved.

The bigger picture around 'Eurocode 2'

Eurocode 2, or officially known as BS EN 1992-1-1. Eurocode 2: Design of concrete structures. General rules and rules for buildings, is a widely used standard nowadays. Not only in the public sector, but also in the private sector, it has replaced BS 8110 to a great extent. As a “Eurocode”, one might think that BS EN 1992-1-1 unifies the design approach across Europe. However, this is not the case. The Eurocode, and further standards that need to be used in conjunction with it, e.g. BS EN 13670 Execution of concrete structures, incorporates the history and requirements in different markets. Country specific adjustments are therefore made in National Annexes, which mainly define Nationally Determined Parameters. An example of this is the permissible yield strength of reinforcement. In addition to these parameters, further documents that provide country specific background information are referenced. The 'National Structural Concrete Specification for Building Construction', also known as 'NSCS 4', is such a document. It is referred to in the National Annex of BS EN 13670 as 'Non-contradictory complementary information'.

Consequences for punching shear systems

An appreciation of this background is essential in understanding the requirements for specific building products, e.g. punching shear reinforcement. The double headed studs, introduced in the 1980’s, are a safe and quick method of catering for punching of columns through slabs. Nowadays, this solution is widely known and used. As a structural component, they need to be designed and specified. EC2 and its National Annex defines the design rules – however they do not ensure the quality of the product used. Therefore, the above mentioned NSCS 4 makes a clear statement: 'All punching shear reinforcement system manufacturers shall hold a valid Technical Approval certificate issued by CARES (…)'. This ensures the quality of the product used by complete traceability of the reinforcement steel and quality control of the manufacturing process. A design according to EC2, however, consequentially requires the usage of a CARES approved punching shear system – which finally ensures the quality of the building.

CE Mark

The request for CE Marked products is becoming increasingly popular. CE Marks are mandatory for products covered by a harmonised European standard (hEN). Punching shear reinforcement is currently not covered by a hEN, therefore CE Marking is not mandatory, however, it can be achieved voluntarily based on a 'European Assessment Document' (EAD). Nevertheless, the CE Mark in this case is still not a quality mark, but only states conformity with the EAD. It therefore cannot replace a CARES approval – furthermore, in reality, none of the CE Marked punching shear products comply with CARES requirements. A design in compliance with EC2 and the respective UK National Annex therefore must not rely on a CE Marked product, but should also consider the usage of CARES approved systems.

Shearail® as a CARES and BBA approved punching shear system

MAX FRANK offer a wide range of reinforcement related products. Shearail® punching shear reinforcement is well known and is the only system available on the market which holds both
CARES and BBA approval, clearly demonstrating the technical benefit of the product.

MAX FRANK provides a design software with graphical CAD output and detailed calculations, which can be downloaded here. MAX FRANK’s technical team supports with the design of punching shear reinforcement and CPD seminars and Design Workshops are offered to all UK Engineering practices.

References:
1. BRITISH STANDARDS INSTITUTION: BS 8110. Structural use of concrete. Code of practice for design and construction. BSI, London, 1985, withdrawn.
2. BRITISH STANDARDS INSTITUTION: BS EN 1992-1-1. Eurocode 2: Design of concrete structures. General rules and rules for buildings. BSI, London, 2004+A1:2014.
3. BRITISH STANDARDS INSTITUTION: BS EN 13670:2009. Execution of concrete structures. BSI, London, 2009.
4. THE CONCRETE CENTRE & CONSTRUCT: National Structural Concrete Specification for Building Construction – Fourth edition complying with BS EN 13670:2009. Blackwater, 2010.
5. BRITISH BOARD OF AGRÉMENT: BBA Agrément Certificate 14/5112. Max Frank Ltd reinforcement systems – Shearail® punching shear reinforcement system. Watford, April 2014.
6. UK CERTIFICATION AUTHORITY FOR REINFORCING STEELS: CARES Certificate 5043. MAX FRANK punching shear reinforcement system for use in accordance with Technical Approval Report TA7 – 5043. Kent, January 2016.

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