Eurocode background
The Eurocodes are the most technically advanced suite of design codes in the world and probably the most wide-ranging codification of structural design ever experienced. Eurocodes are intended to be a CEN (Comité Europeen de Normalisation) standard for buildings as a ‘passport’ for designers between EU countries. From March 2010 they are to be used as the principal codes to demonstrate compliance with the UK Building Regulations and the requirements of other public authorities. There are 10 codes, with each being split into a number of subsections (not listed here):
These codes cover the principles, rules and recommended values for ultimate limit state struc- tural design. However, safety, economy and durability have been ‘derogated’ to the member states, and for each Eurocode there is a supplementary National Annexe which must be con- sulted in parallel. Allowing for regional variations, the UK National Annexes have adjusted Eurocode values and methods to bring these into line with standard UK practice. These changes are termed Nationally Determined Parameters (NDPs). The British Standards Institute cannot change any text in the core CEN document nor publish a version of the CEN docu- ment with the values of the NDPs pasted in, but the National Annex may include reference to non-contradictory complimentary information (NCCI), such as other non-Eurocode national standards or guidance documents, for example information from Access Steel.
An additional complication is that while British Standards included design guidance along- side materials and workmanship requirements, the Eurocodes rely on separate standards for materials and workmanship. Also several topics typically covered in significant detail in British Standards have been omitted, so that the provision of supplementary technical information is essential in some areas. It is not considered safe or appropriate to adopt a ‘pick and mix’ design due to fundamental differences in philosophy, safety factors, underlying assumptions and construction detailing issues. Structures should be designed to either Eurocodes, or British Standards, not to a mixture of both.
To help keep the documents concise, Eurocodes are divided into ‘Principles’ and ‘Application Rules’. Principles are normally general statements, definitions, models and requirements for which no alternative is permitted. This is indicated by the use of ‘P’ after the clause num- ber. Applications rules give users design methods which follow the requirements described by the Principles. While it is possible to use alternative rules to demonstrate compliance with Eurocode Principles and produce a safe and economic design, any design which has not used the Application Rules cannot be called ‘Eurocode Compliant’ or obtain the equivalent of a CEN. This may be relevant to those who are contracted to provide Eurocode building designs under EU Public Procurement Directive rules or at their client’s request.
BS EN 1990 Basis of design 1991 Actions 1992 Concrete 1993 Structural steelwork 1994 Composite steel and concrete
1995 Timber
1996 Masonry
1997 Foundations 1998 Seismic
Preparation of the Eurocode suite has been at glacial pace, with the whole process having taken over 25 years to get to the March 2010 implementation date. From this date the British Standards were ‘Withdrawn’ (which is not the same as outlawed) and the Eurocodes became current. In addition to design codes, engineers rely on a large amount of support documenta- tion (e.g. textbooks, software, proprietary products) and it will take some time for this informa- tion to become fully available. In 2014, this process is not yet complete, with coverage being patchy when designs other than the most straightforward cases are considered.
Engineers need to refer to several Eurocode documents in place of one British Standard: the Eurocode, the National Annexe, the NCCI and the British Standard for materials and workman- ship. British Standard users will have to familiarise themselves with a fairly daunting array of changes to both design vocabulary and notation. Some of these changes appear to stem from philosophical changes in the design approach and standardisation of symbols across Europe, but other (less obvious ones) appear to stem the need for precision when translating between other European languages. Some of the most common alterations are as follows:
The cumulative effect of the changes in language, notation, technical approach and layout is quite considerable, particularly for those familiar with British Standards. It is therefore likely that it will take quite some time for Eurocodes to be fully adopted by established designers – especially when the new codes produce similar answers as British Standards and limit the use of quick/simple hand calculations. While many argue that the Eurocodes offer better nuance and scope for international work, others cite commercial reasons and limited benefits for the slow adoption. Whatever view is taken, the example of BS449 for steelwork design (still in use by practising engineers nearly 20 years after the introduction of BS5950) is probably a fair indicator of how speedy the full Eurocode transition will be.
For safety and simplicity, this book will use the UK convention of ‘.’ for the decimal point throughout instead of using the Eurocode convention of ‘,’. This is in line with the convention used in about half of the UK National Annexes.
Eurocode English translation
Action Load phenomena (including temperature, inertia, etc.) Effect of actions Stress/strain/deflection/rotation
Permanent action Dead load
Variable action Live load
Execution Construction process
Auxiliary construction works Temporary works
‘ + ’ To be combined with