Compliance with Eurocodes

by Alan Murray
NBS Technical Author

Eurocodes are becoming the required design standards for all building and civil engineering works in the UK, Europe and across the global construction market. After 31 March 2010, they replaced the previous British Standards for design in the UK. This article describes how NBS are managing the application of their structural specifications during this transition.

This affects specification of building and geotechnical structures and structural cladding in two respects:

• Design requirements for elements in the design of the Contractor or his supplier must be specified to the appropriate Eurocode and sufficient information provided concerning the structural use of the element and its environment as to ensure its adequacy for the working life of the building
• For the completed work to be Eurocode compliant, structural materials and execution must comply with the appropriate Eurocode, whether the design is prepared by the Employer's Engineer, the Contractor or his supplier.

NBS are implementing these requirements by:

• The preparation of new section B50 to cover general structural requirements for compliance with Eurocodes
• Updating the structural work sections, e.g. section G10 for steel, to be compatible with section B50
• Replacing references to BSI standards by the CEN (BS EN) standards referenced in Eurocodes and execution standards as the BS EN standards are published
• Introducing new BS EN standards for structural work not covered by BSI standards when this is appropriate.

Work on updating reference standards has been underway for some time and is continuing. Section B50 is included in Update 2010-1, and revisions of the main structural work sections which will refer to B50 should be included in Update 2010-2 and beyond.

British Standards that conflict with Eurocodes will be withdrawn on 31 March 2010. They will remain available from BSI but will no longer be updated, so they may not be suitable for some aspects of structural design. Designers can continue to specify projects in the private sector to British Standards in the short term. However, in England, Wales and Northern Ireland, public sector projects (and those for statutory authorities and product manufacturers) must be specified to Eurocodes .The implementation of the Eurocodes that replace British Standards will not be immediate and there will be a period of transition as the use of Eurocodes becomes better understood by designers and regulating authorities. Designs started before 31 March, using British Standards that are to be withdrawn, will be valid.

Useful reading is included in an article published in The Proceedings of the Institution of Civil Engineers, February 2010 (also on the ICE website). The article is entitled Eurocodes: the new British Standards for structural design by Professor Haig Gulvanessian, Chaiman of ICE's Eurocodes expert Panel. It refers to legal proceedings relating to structural design where the Eurocodes will most likely be referred to for dispute resolution.

Section B50 – General structural requirements

The original concept for section B50 was to gather together in one place all general Eurocode requirements , thus avoiding repetition of the same general requirements in multiple sections. We quickly realised that this would be unsatisfactory in the interim period while Eurocodes and British Standard design Codes of Practice (BS codes) coexist for design. Hence, we have extended section B50 to cover both types of code.

For contractual purposes, some requirements need to be named or briefly described in the Preliminaries sections and amplified in either section B50 or in the relevant work section (but not both). Advice on this has been included in section B50 general guidance 1.1.

Features that have been introduced in section B50 include:

• Designated codes of practice (clause B50/120): This defines the codes to which structural work has been designed or with which Contractor designed elements must comply. Also, the completed structure is required to comply with the designated codes and the standards referenced therein.
  
  Having been named in section B50, the standards are referenced in the work sections as 'the designated codes of practice'. Hence, a material such as concrete which occurs in a number of work sections will always be required to comply with either BS 8110 or BS EN 1992 (whichever has been designated in section B50), without naming BS 8110 or BS EN 1992 in the work section.
  
  This has the added advantage that to change a specification where the structure has been designed to BS Codes for use on a project designed to Eurocodes, it will only be necessary to change the designated codes of practice in one clause.
• A structure can be either a 'building structure' or a 'geotechnical structure', but the term 'structure' is reserved for the description of work designed to a BS code or a Eurocode. Other properties, e.g. weathertightness, are referred to in the work sections as 'Functional requirements'.
• The preparation of a 'geotechnical design report' (general guidance 5.3 and clause B50/160) has been introduced for geotechnical work as a requirement when design is to comply with Eurocodes, and as good practice for design to BS Codes. Provision is also made for monitoring ground conditions during construction to identify differences between actual ground conditions and those assumed in the design and for testing when necessary to demonstrate the adequacy of the geotechnical design.
• Monitoring of disturbance to and movements of existing structures and general requirements for monitoring new structures is covered in clauses B50/250 to 310 (250 to 290 in Intermediate Version) and 760 to 790.
• Tests to demonstrate the adequacy of the design remain in the work sections, e.g. performance tests for piles are still covered in clause D30/280.
• Consideration of conflicts in documentation. If a conflict occurs between the specification and referenced documents, Preliminaries section A31 requires the specification to prevail.
• Clause B50/700 provides an opportunity for reconsideration for structural elements. Similarly, notwithstanding tolerances specified elsewhere, clause B50/700 limits tolerances to the requirements of the designated code.

Section B50 contains Contractor's design requirements for:

• The submission of information at time of tender
• The naming of the Engineer responsible for overall stability of the structure
• Design supervision/ checking, quality control and maintenance
• Assessment of ground conditions
• Performance criteria.

The structural work sections define additional Contractor's design requirements for:

• The scope of the Contractor's design responsibility in that work section and reference any associated design work in other sections, e.g. for an in situ concrete retaining wall, scope for the geotechnical design will be specified in section D20 and for the concrete structure will be specified in section E05.
• Any modifications/ additions to the requirements of section B50.
• Detailed requirements for the content and timing of submission for design and production information.

Further updates to work sections are underway to ensure that they will be fully compatible with section B50. Until that process is complete, specifiers will need to ensure that the same requirement is not specified in both section B50 and the work section. This will entail the omission of some clauses in the work section, e.g. loading clauses and the editing of others, e.g. Contractor's design clauses.

Related NBS information:

Articles:

• Currency of NBS with respect to Eurocodes
• NBS and the structural Eurocodes
• Calibration report for Eurocode 1 on wind actions

Selected links:

• Civil and structural engineering, general

Written March 2010

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