Introducing the Eurocodes

Introduction

On the 31st of March 2010, British Standard Institution (BSI) withdrew the 57 parts of the British Standards and other conflicting Standards for the 58 parts of the Eurocodes. The British Standard Institution has since made public declarations for all public works to be in accordance with the Eurocodes. It was also made public that the withdrawn standards will not be updated nor will it be revised. It is almost 10 years now since the standards were withdrawn which suggests that the design codes are now obsolete.

In several countries including Nigeria, the British standard has been adopted almost exclusively with the exception of variation of nationally determined parameters within the codes. Surveys have continued to show that a majority of Nigerian engineers, lecturers, students, graduates are not aware of this replacement and dangers associated with the use of withdrawn standards. Even though the Nigerian Institution of structural engineers developed a document for the structural design of structures in Nigeria, it was a nothing but a monotony of the already withdrawn BS codes.

The benefits of using the Eurocodes cannot be over-emphasized. Numerous literatures have continued to show that the Eurocodes are very economical in design and less prescriptive allowing each country the flexibility to impose certain safety parameters based on variations in construction practices, environmental conditions amongst others within countries.

The Eurocodes are seen as leading the way in structural codes. Their flexibility enables adoption and use not only within Europe but internationally. This feature has been recognized by several countries outside Europe and they are already committed to adopting Eurocodes. This post under this series aims to introduce the Eurocode to engineers new to the Eurocode but already familiar with the withdrawn BS codes.

Structure of the Eurocodes

There are ten separate Structural Eurocodes Each Eurocode comprises a number of ‘Parts’, which are published as separate documents. The full text of each Eurocode Part is issued initially by the (European Committee for Standardization) in three languages with the above ‘EN’ designations; national standards bodies may translate the text into other languages but may not make any technical changes

The Eurocode text is then provided with a front cover and foreword by each national standards body and published within that country using a designation with the national prefix – for example EN 1990 is published by BSI as BS EN 1990. The text may be followed by a National Annex or a National Annex may be published separately.

CEN documents

EN 1990 Eurocode: Basis of Structural Design
EN 1991 Eurocode 1: Actions on Structure
EN 1992 Eurocode 2: Design of Concrete Structures

EN 1993 Eurocode 3: Design of Steel Structures
EN 1994 Eurocode 4: Design of Composite Steel & Concrete Structures
EN 1995 Eurocode 5: Design of Timber Structures

EN 1996 Eurocode 6: Design of Masonry Structures
EN 1997 Eurocode 7: Geotechnical Design
EN 1998 Eurocode 8: Design of Structures for Earthquake Resistance

EN 1999 Eurocode 9: Design of Aluminum Structures

The Eurocode parts contain two distinct types of statement “Principles” and “Application rules”. The former must be to achieve compliance with the principles, the latter are rules that aid compliances with the principles but its permissible to use alternative design rules, provided that they do not contradict the principles.

Within the text of the Eurocode provision is made national choice on some parametrs and choice of design methods (i.e the selection of a particular application rule). these choices are generally reffered to as the Nationally determined Parameters (NDP’s) and are published in the National Annex to the part been used.

National Annex

The National Annex (NA) is an essential document when using a Eurocode Parts. The national annex allows a country to impose safety factors such as

Specify the value of a factor, to modify limiting values or a formula
Specify which design method may be used

Although the NA may specify the value of partial factors to be applied to Actions and resistances, in many cases it simply accepts the value recommended in the Eurocode text.

NCCI

The National Annex may give references to publications that contain non-contradictory complementary information (NCCI) that will assist the designer when designing a structure to the Eurocodes. According to CEN rules, an NA cannot contain NCCI, but references to NCCI may be given. As the name suggests, any guidance that is referenced in the National Annex must not contradict the principles of the Eurocode.

The Eurocodes omit some design guidance where it is considered to be readily available in text books or other established sources. Publications that contain such design guidance may be referenced in the National Annex as NCCI.

Additional Information

In most of the Eurocode parts, Principles are denoted by the letter ‘P’ after the clause number for example 1.2(3)P. Whereas application rules are not denoted by letter P e.g 1.2.(3).

Supplementary provisions for the design of buildings in some general parts are denoted by letter B after the clause number for example 1.2.(3)B.