Introducing Second Generation Eurocode 2

The revised design code could usher in a new generation of more efficient structures and lower-carbon concrete and reinforcement. Tony Jones outlines what to expect, and when

A new suite of Eurocodes, branded the “Second Generation Eurocodes”, is in the process of being introduced across Europe. For concrete, the requirements for the vast majority of structures are contained in Eurocode 2 (see box, next page), which could be published in the UK as early as next year. It is set to have a major influence on the environmental impact of concrete, with significant changes that will encourage the use of a wider range of concretes and reinforcement with lower embodied carbon, as well as recycled aggregates and more efficient designs.

Programme to publication

At the time of writing the Second Generation documents had just passed the Formal Vote stage. Once any editorial comments have been addressed, the documents will be made available to national standards bodies (NSBs). It is then down to NSBs to determine the timing of publication and implementation in their country, but the documents must be published by the end of 2027 and conflicting standards withdrawn in 2028.

For the UK, the British Standards Institution (BSI) is expected to receive the final document in October 2023. For the industry to use the new Eurocodes, National Annexes will also need to be published. These permit each country to adjust key factors that can have a significant impact on the efficiency of the structures produced. As no technical changes are expected prior to the approval of the current version of the document, preparation of the UK National Annexes has already started and it is hoped that a draft of the National Annex, for public comment, will be available soon after BSI receives the final version of the Eurocode. This means that the Second- Generation and its UK National Annex could be available for use as early as summer 2024.

The Eurocodes and the associated product standards provide an interlinked framework of rules. Publishing an update to one part of the framework may cause problems at the interfaces with other documents. For example, the steel and concrete composite part of the Eurocode relies on the current structural concrete Eurocode for many of its provisions. Similarly, precast concrete product standards refer to rules in the current concrete Eurocode. Therefore, there is likely to be a period of coexistence, with both the current Eurocode and the Second Generation being available.

BSI is currently considering what this means contractually, and it is likely that wording in the National Foreword to the Second Generation will state that the existing Eurocodes remain “current” until withdrawn prior to 2028. On the face of it, this would seem to preclude the use of the Second Generation, but the way the UK Building Regulations are implemented means that there is nothing to prevent an engineer using the documents. It may, however, be prudent to agree this on a project basis with your client.

The period of coexistence will also allow supporting resources to be updated. The Eurocodes are detailed and extensive, applicable to a wide range of structures. While early adopters at specialist practices or major consultancies may have the expertise to implement the new standard directly, using the raw document will be a significant burden for many engineers. Experience shows that developing simplified guides, explanations of key changes and principles, and simple software for typical cases all ease the adoption of new codes of practice.

MPA The Concrete Centre provides a significant set of resources, including technical guidance documents, webinars, courses and spreadsheets for the current Eurocode. The key resources will be updated before the existing code is formally withdrawn.

Key changes to Eurocode 2

It is worth highlighting technical changes that have the greatest potential to impact the industry. New models have been introduced for certain key areas of behaviour. In some cases, these would lead to more conservative designs, and calibration work is ongoing to see if, where justified, this can be addressed in the National Annex. In other cases, models have been introduced that have the potential to enable more efficient design of columns, for example.

Some simplified design methods have been removed – generally where they have proved contentious by reflecting one nation’s historic practice above others. National bodies can provide their own simplified methods, as long as they can be shown to be consistent with the more detailed models within the code. These additional methods are referred to as non- contradictory complementary information (NCCI). MPA The Concrete Centre is working with the industry to develop this in parallel with the National Annex and it will be published in due course.

Completely new areas covered by the Second Generation include:

• Information on the background to the safety factors used. This allows the factors to be reduced, and hence a more efficient design produced, where there is more certainty in the material properties than assumed in the derivation of the default factors.
• Assessment of existing concrete structures, encouraging reuse and adaption and therefore supporting the “long-life” argument for concrete structures.
• Strengthening of structures with carbon-fibre reinforcement polymers. This will likely be used most in conjunction with the assessment of existing structures.
• Structural use of steel fibre reinforced concrete. While already used in basic applications, the codification of these rules will allow wider use of the material where it is the most efficient solution.
• The use of recycled aggregate concrete in structures. This formalises the use of the material and provides guidance on the design implications, which is currently missing.

Photos Tarry + Perry, Laing O’Rourke, Chris Mansfield