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"Member States should use the recommended values provided by the Eurocodes when nationally determined parameters have been identified in the Eurocodes. They should diverge from those recommended values only where geographical, geological or climatic conditions or specific levels of protection make that necessary.
Member States should, acting in coordination under the direction of the Commission, compare the nationally determined parameters implemented by each Member State and assess their impact as regards the technical differences for works or parts of works. Member States should, at the request of the Commission, change their nationally determined parameters in order to reduce divergence from the recommended values provided by the Eurocodes."
Commission Recommendation 2003/887/EC

Further Harmonization of the EN Eurocodes

The EN Eurocodes are the result of a long procedure of bringing together and harmonizing the different design traditions in the Member States. In the same time, the Member States keep exclusive competence and responsibility for the levels of safety of works. The differences in the environmental conditions and in the ways of life in the Member States also require flexibility in the National Application of the EN Eurocodes.

Therefore the EN Eurocodes include Nationally Determined Parameters (NDPs) which

  • take into account differences in geographical, geological or climatic conditions;
  • result from different design cultures and procedures for structural analysis;
  • arise from the requirement for safety levels in the relevant Member States.

Member States are encouraged to minimize the number of cases where recommendations for a value or method are not adopted for their NDPs. The principal objectives of further harmonization are as follows

  • the reduction of NDPs in the EN Eurocodes resulting from different design cultures and procedures in structural analysis;
  • the reduction of NDPs and their variety through the strict use of recommended values;
  • the gradual alignment of safety levels across Member States.

It is important to harmonize not only the values of the NDPs (harmonization across national borders), but also the methodologies used for their assessment, as well as the design procedures used for different structures (harmonization across different materials), e.g. reinforced concrete, steel and composite structures.

Further harmonisation of the EN Eurocodes will be achieved through collaboration within CEN/TC250, National Authorities, International Technical Scientific Organisations, Industry and the Commission/JRC.

In the mandates M/466 EN pdf-download and M/515 EN pdf-download for amending the existing Eurocodes and extending the scope of structural Eurocodes, the European Commission requested CEN to assess all existing Eurocodes concerning the potential to significantly reduce the number of Nationally Determined Parameters. This work should be done in close collaboration with the JRC and be based on the NDPs as defined on National level and uploaded in the specific NDP database.