What does the new Eurocode 2 for the design of concrete structures bring us?

A public debate is underway for the new Eurocode 2 – a radically different standard that is more modern and comprehensive.

The construction community in Serbia has long been waiting for new standards for the design of concrete structures. Since 2004, when in the member states of the European Committee for Standardization (European Committee for Standardization, CEN) started national implementation Eurocode 2 (EN 1992) a great deal of work was done by experts from the Institute for Standardization of Serbia (ISS), faculties of civil engineering and companies in translating this standard and preparing the so-called national annex (NA) which defines the parameters for which selection is allowed in individual countries.

On January 1, 2017, ISS became a full member of CEN, which provided an opportunity for domestic experts to be actively involved in the work of European technical bodies, ie to attend meetings of these bodies, participate in decision-making and writing European standards. In 2019, the legislator announces Rulebook for building constructions (Official Gazette of RS No. 89/2019 with amendments 52/2020 and 122/2020) within the list of standards for the design of building structures. In this way, Eurocode 2 (now in the official version for Serbia SRPS EN 1992-1-1: 2015) was proclaimed valid standard for the design of concrete structures (with the transitional period of parallel validity of Eurocode 2 and the previous Rulebook “BAB 87”).

CEN and continuous work on standardization

Although Eurocode 2 was published in 2004, CEN did not stop working then. Moreover, since then, the use of Eurocode 2 has been analyzed as well as the possibilities for its improvement. What does it look like in practice?

CEN is an organization made up of all European Union (EU) countries as well as Iceland, Norway, Switzerland, the United Kingdom, Northern Macedonia, Serbia and Turkey. Through its technical committees, subcommittees and working groups, CEN is responsible for drafting all European standards that apply in the member states. One group of standards consists of standards for the design of building structures, ie Eurocodes (with numbers 0 to 9, ie 1990 to 1999, Figure 1).

Eurocode structure (source)

Eurocode 2 has been declared a valid standard for the design of concrete structures with a transitional period of parallel validity of Eurocode 2 and BAB 87.

In areas where harmonization between EU Member States is important, CEN receives a Mandate (request for drafting standards) directly from the European Commission (EC). Precisely with such a mandate, M / 466 EN from May 19, 2010 initiated work on the first generation of Eurocode standards. This mandate was later updated by mandate M / 515 EN on 12 December 2012, which provided the basis for the second generation of Eurocodes.

The development of Eurocodes is assigned to Technical Committee 250 (CEN / TC 250) whose current structure is shown in Figure 2. Eurocode 2 for the design of concrete structures is under the authority of Subcommittee 2 (CEN / TC 250 / SC 2) within which the “operational” part of the work is performed working group 1 (CEN / TC 250 / SC 2 / WG 1). In other words, representatives of CEN member states participate in the work of subcommittee 2, while only the “writing” of standards is done by individual experts in working group 1.

Structure of CEN 250 technical committee (source)

Draft of the new Eurocode 2

Since receiving the mandate, subcommittee 2 and working group 1 have been working on the draft of the new Eurocode 2, on parts 1-1, ie general rules – rules for buildings, bridges and civil engineering and 1-2, ie. general rules – design of structures on fire action.

The work included the engagement of leading experts in the field of concrete and concrete structures to improve existing and adopt new calculation models as well as to expand the scope to include new materials that have become available in the meantime (but also sufficiently researched).

After 7 working versions of the text of the standard, there was a version that in part 1-1 contains 375 pages of text and 75 pages in part 1-2, ie significantly more than the current versions (Figure 3). This is largely due to the new contributions as well as the fact that the previous part 2 (EN 1992-2) for the design of concrete bridges and part 3 (EN 1992-3) for tanks and silos have become “only” contributions in part 1-1.

Figure 3. Title page of the draft of the new part 1-1 of Eurocode 2; Photo: ISS

What does the new Eurocode 2 bring?

The draft of the new Eurocode 2 brings significant changes both in the basic text of the standard and in a number of annexes, of which there are 13. In the basic text, there are numerous changes in the characteristics of the material, of which it is worth noting new expressions for design values ​​of compressive and tensile strength, modulus of elasticity, as well as new models for calculation of deformations due to shrinkage and yield.

Another (potentially) major change is in the durability section where it is proposed radically different concept of determining the protective layer by determining the so-called. exposure resistance class (XRC) resp. classes of resistance of concrete to exposure to environmental influences. However, this part is not necessarily mandatory because each CEN member can replace it with Annex P, which is equal to the current provisions of Eurocode 2 for durability.

There are also changes in certain budget models, above all on shear and breakthrough where completely new expressions and models have been adopted in relation to the current Eurocode 2. There are then changes in shaping, anchoring and overlapping reinforcement.

However, probably the biggest changes, ie novelties, are brought by the articles. The new part 1-1 of Eurocode 2 brings us, among other things:

  • new and improved attachments for modification of partial coefficients, calculation of deformations due to shrinkage and flow, evaluation of existing structures, design of concrete bridges and concrete with light aggregates;
  • brand new attachments for steel fiber reinforced concrete (steel fibre reinforced concrete), reinforced concrete structures carbon strips and canvases, concrete structures reinforced with bars of polymer reinforced fibers (fibre reinforced polymer) i concrete with recycled aggregate.

As for Part 1-2, it also brings novelties in calculation models (indirect and direct, simplified and rigorous) as well as in annexes that also cover new materials (such as steel fiber concrete and recycled aggregate).

Overall, the new Eurocode 2 brings a handful of newspapers and represents not only an incremental change over the existing version but a radically different standard that is more modern and comprehensive and accompanied by rich background documentation that justifies any change.

Public debate and next steps

Although there is already a “complete” version of the new Eurocode 2, it is still not final. The reason for this is the process of adopting standards within CEN. Namely, the new versions of parts 1-1 and 1-2 are draft standards for public discussion (CEN Inquiry phase). This is the period during which everyone can have an insight into the draft standard and submit comments in the form of proposals for amendment through their national standardization organization.

In this case, The CEN public hearing began on September 2, 2021. and lasts until 23.12.2021. In our country, the public debate on draft standards lasts a bit shorter, 60 dana, and in that period all interested parties can submit their comments via web site ISS. Draft standards for public discussion are available on the ISS website, ie. the search of the “1992” standard leads to documents on SRPS EN 1992-1-1: 2020 and naSRPS EN 1992-1-2: 2020 which can be read free of charge during the period of public debate.

It is a clear responsibility of each member of the construction community to adopt the best possible standard.

During the period of public debate, the ISS commission responsible for Eurocode 2 (U250-2 led) prof. Dr. Dušan Najdanović) will prepare comments and the cooperation of the entire construction sector on the best and most detailed preparation is welcome – the commission will, after 60 days from the beginning of the public debate, consider all received comments at the session.

Following the CEN public hearing, subcommittee 2 and working group 1 of the CEN / TC 250 committee will analyze the comments and implement any changes it deems necessary, and then the updated text of the standard will go to a formal vote (formal vote) in which CEN member countries vote. Formal voting for the new Eurocode 2 is scheduled for the first quarter of 2022. After that, each country decides when to publish the new standard, but it must be by the end of the first quarter of 2027 at the latest. withdraw by the end of the first quarter of 2028 at the latest.

From the above, it is clear the responsibility of each member of the construction community to adopt the best possible standard because it will have a direct and immediate long-term impact on the economy and society.

When you are already here…

Source: Gradnja by www.gradnja.rs.

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