Standardization system in Europe
The standardization system in Europe is based on the national pillars, which are the National Standardization Bodies or the members of CEN. It is the responsibility of the CEN National Members to implement European Standards as national standards. The National Standardization Bodies distribute and sell the implemented European Standard and have to withdraw any conflicting national standards.
Eurocodes are intended to be applied uniformly across the CEN’s members or National Standardization Bodies (NSBs) of the 27 European Union countries, United Kingdom, the Republic of North Macedonia, Serbia, and Turkey plus three countries of the European Free Trade Association (Iceland, Norway, and Switzerland).
The Eurocodes are a series of European standards which provide a common series of methods for calculating the mechanical strength of element playing a structural role in construction works. Those methods make it possible to design construction works, to check the stability of construction works or part thereof and to give the necessary dimensions of structural construction products. The Eurocodes cover all principal construction materials (concrete, steel, timber, masonry and aluminium), all major fields of structural engineering (basis of structural design, loading, fire, geotechnics, earthquake, etc.) and several types of structures and products (buildings, bridges, towers, silos, etc.).
The verification procedure is based on the limit state concept used in conjunction with partial safety factors. The Eurocodes also allow for designs based on probabilistic methods as well as for designs assisted by testing and provide guidance for the use of these methods. The Eurocode Suite includes ten European Standards:
- EN 1990 – Eurocode: Basis of Structural Design.
- EN 1991 – Eurocode 1: Actions on Structures.
- EN 1992 – Eurocode 2: Design of Concrete Structures.
- EN 1993 – Eurocode 3: Design of Steel Structures.
- EN 1994 – Eurocode 4: Design of Composite Steel and Concrete Structures.
- EN 1995 – Eurocode 5: Design of Timber Structures.
- EN 1996 – Eurocode 6: Design of Masonry Structures.
- EN 1997 – Eurocode 7: Geotechnical Structures.
- EN 1998 – Eurocode 8: Design of Structures for Earthquake Resistance.
- EN 1999 – Eurocode 9: Design of Aluminium Structures.
Each of these codes, except EN 1990, is divided into a number of Parts covering specific aspects of the subject. In total there are 58 Eurocode Parts distributed in the ten Eurocodes.
The goal is to harmonize design practices and ensure consistency in structural design and construction methods within the EU. Therefore, the content of Eurocodes is generally the same across countries.
However, each member state has the responsibility to formally adopt the Eurocodes into its national standards. During this adoption process, some countries may choose to make certain modifications or provide additional guidance to suit their specific needs or to align better with their national regulations and practices. These national adaptations are known as National Annexes.
For example, the UK and Germany, being CEN member states, adopt Eurocodes as part of their national standards. However, they have their own National Annexes that provide country-specific parameters and values to be used in conjunction with the Eurocodes. The National Annexes are used to customize the Eurocodes to suit the specific conditions and requirements of each country.
In summary, while the core Eurocode principles are consistent, there may be variations at the national level due to the use of National Annexes.
Nationally Determined Parameters
The determination of the levels of safety of buildings and civil engineering works and parts thereof is, and remains, within the competence of CEN Members. The national standard implementing the EN Eurocodes in a country can have a National Annex, which is usually published by the relevant National Standardisation Body (NSB) and contains all national choices to be used for the design of buildings and civil engineering works to be constructed in the relevant country.
Possible differences in geographical or climatic conditions (wind or snow maps) or in ways of life, as well as different levels of protection that may prevail at national, regional or local levels can be taken into account by choices left open about values, classes, or different methods that are identified in the Eurocodes to be determined nationally.
The values, classes or methods to be chosen or determined at national level (called National determined parameters) will allow the CEN member states to choose the level of safety, including aspects of durability and economy applicable to works in their territory and they include:
- Values and/or classes where alternatives are given in the Eurocodes:
For example: Table NA.A1.1 — Values of Ψ factors for buildings (NA to BS EN 1990:2002+A1:2005)
| Load Category | Ψ0 | Ψ1 | Ψ2 |
|---|---|---|---|
| Category A: domestic, residential areas | 0.7 | 0.5 | 0.3 |
| Category B: office areas | 0.7 | 0.5 | 0.3 |
| Category C: congregation | 0.7 | 0.7 | 0.6 |
| Category D: shopping | 0.7 | 0.7 | 0.6 |
| Category E: storage area | 1 | 0.9 | 0.8 |
| Category F: traffic area vehicle weight ≤30kN | 0.6 | 0.7 | 0.7 |
| Category G: traffic area 30 < vehicle weight ≤ 160kN | 0.7 | 0.5 | 0.3 |
| Category H: roofs | 0.7 | 0 | 0 |
| Snow Loads, H > 1000 m a.s.l. | 0.7 | 0.5 | 0.3 |
| Snow Loads, H ≤ 1000 m a.s.l. | 0.5 | 0.2 | 0 |
| Snow Loads, H ≤ 1000 m a.s.l. | 0.5 | 0.2 | 0 |
| Wind loads on buildings | 0.5 | 0.2 | 0 |
| Temperature (non-fire) in buildings | 0.6 | 0.5 | 0 |
Table A1.1 DK NA Ψ factors for buildings (DS/EN 1990 DK NA:2021)
| Load Category | Ψ0 | Ψ1 | Ψ2 |
|---|---|---|---|
| Category A: domestic, residential areas | 0.5 | 0.3 | 0.2 |
| Category B: office areas | 0.6 | 0.4 | 0.2 |
| Category C: congregation | 0.6 | 0.6 | 0.5 |
| Category D: shopping | 0.6 | 0.6 | 0.5 |
| Category E: storage area | 0.8 | 0.8 | 0.7 |
| Category F: traffic area vehicle weight ≤30kN | 0.6 | 0.6 | 0.5 |
| Category G: traffic area 30 < vehicle weight ≤ 160kN | 0.6 | 0.4 | 0.2 |
| Category H: roofs | 0 | 0 | 0 |
| Snow Loads, for combination with Leading imposed loads of category E or leading thermal actions | 0.6 | 0.2 | 0 |
| Snow Loads, for combination with Leading wind actions | 0 | 0 | 0 |
| Snow Loads, for all other conditions | 0.3 | 0.2 | 0 |
| Wind Loads, for combinations with a leading imposed load of category E | 0.5 | 0.2 | 0 |
| Temperature (non-fire) in buildings | 0.6 | 0.2 | 0 |
| Wind Loads, for all other conditions | 0.3 | 0.2 | 0 |
| Thermal actions | 0.6 | 0.5 | 0 |
- Values to be used where only a symbol is given in the Eurocodes.
- Country-specific data (geographical, climatic, etc.).
- Procedures to be used where alternative procedures are given in the
Eurocodes:
For example, the choice between equation 6.10, or 6.10a and 6.10b for Combinations of actions for persistent or transient design situations (fundamental combinations) made in the National annex.
NA to BS EN 1990:2002+A1:2005 : Either expression 6.10, or expression 6.10a together with and 6.10b may be made, as desired.
NF EN 1990/NA:2011-12 : For the application, in France, of Table A1.2(B) of European Standard EN 1990:2002 to the design of buildings, it is appropriate to take into account the fundamental combination of actions defined by expression 6.10.
DS/EN 1990 DK NA:2021 : Equations 6.10a and 6.10b are applied for STR as well as GEO. Equation 6.10a relates only to permanent actions.
The National Annex may also contain the national choice on the application of informative annexes (In relation to the national choice on the application of an informative annex, a Country may: (i) permit its use, (ii) prohibit its use in full or in part, (iii) stay silent on whether to use it or not)
The National Annex may contain, directly or by reference, non-contradictory complementary information for ease of implementation, provided it does not alter or contradict any provisions of the Eurocodes
Additional Information
- National Annex is published by the National Standards bodies on behalf of and with the agreement of the national competent authorities.
- A National Annex is not required if the EN Eurocode part is not relevant for the Member state – for example seismic design for some counties where there is low seismic activity.
- A National Annex cannot change or modify the content of the Eurocode text in any way other than where it indicates that national choices may be made by means of Nationally Determined Parameters.
For example, EN 1990 gives three alternative proposals in two instances:
- The expressions combining action effects
- Soil/structure interaction
The National Annex will make a choice of one of the alternatives. Annexes are not transferable – Each CEN member state will have a different National Annex.
For example, a UK designer will have to use the appropriate Eurocode with the UK National Annex when designing a building in the UK, and the same designer will have to use the Eurocode with the German National Annex when designing a building in Germany
Challenges and learnings in National Annexes Implementation in CLT Toolbox
We are implementing National Annexes for the UK, Germany, France, Norway, Denmark, Spain, Italy, The Netherlands, Finland, and Sweden.
Each National Annex refers to specific national standards – because these references help adapt the Eurocodes to the specific technical, regulatory, and construction practices of each country. The references to national standards in the National Annexes ensure that the Eurocodes are applied in a manner consistent with the national context.
For example, DIN EN 1995-1-1/NA (2013) refers to DIN EN 1995-1-1:2010-12, and the National Annex for the UK, NA to BS EN 1995-1-1:2004+A2:2014, refers to BS EN 1995-1-1:2004+A2:2014.
Although Eurocodes are intended to be a common set of design standards for the CEN member, each country has its own long-standing standards and practices. By referencing national standards in the National Annexes, the Eurocodes can be adapted to align more closely with existing national standards.
Also, references to specific editions of national standards in the National Annexes also help manage transitional periods. This is important when new editions of Eurocodes are published, and there is a need to ensure a smooth transition from older versions to the latest ones – this is exactly what is happening with the new series of Eurocodes.
Also, some calculations that we have implemented according to the new draft version of Eurocode 5 do not have an appropriate national annex. Since these codes are in the process of development, and National Annexes will be published in the next few years, we are not able to cover these calculations with current National Annexes. For those situations, we will implement national annexes when released for the new Eurocode and, where possible, add calculations according to the current Eurocode with appropriate National Annexes accordingly (as for Large Dowel/bolt calculators).
Also, there is a challenge with material selection and National Documentation related to. Each standard for material definition has a version according to each country. For example, values according to BS EN 338:2016 are defining strength, stiffness properties and density for timber classes. Some of these numbers could be different to the same material in another country.
Author
Marko Dimitrijevic
