Eurocode 2: Design of concrete structures

An example of a concrete structure

EN 1992, also known as Eurocode 2: Design of concrete structures, is the European Standard for the design of concrete, reinforced concrete and prestressed concrete structures, using the limit state design philosophy. It was approved by the European Committee for Standardization (CEN) on 16 April 2004 to enable designers across Europe to practice in any country that adopts the code. There is however, one proviso, the design of buildings in a specific country requires the National Annex for that country to be applied in the design. The National Annex for the UK for example contains all the nationally determined parameters which refer specifically to the UK due to our unique circumstances.

Eurocode 2 is subdivided into the following parts:

EN 1992-1-1: General rules, and rules for buildings

Concrete is a very strong and economical material that preforms exceedingly well under compression. Its weakness lies in its capability to carry tension forces and thus has its limitations. Steel on the other hand is the opposite; whilst it is strong in tension, it is extremely weak in compression. Combining these two materials means engineers would be able to work with a composite material that is capable of carrying both tension and compression forces.

EN 1992-1-1 deals with the rules and concepts required for designing concrete, reinforced concrete and prestressed concrete structures. There are three main stages are involved in the design of elements in these structures:

• Pre-design: Before any other designing is undertaken, the limit states of durability and fire design are considered in order to ascertain the required cover to the reinforcement, the minimum size of members and the appropriate concrete strength.
• Ultimate limit state: Accurate section sizes are determined for corresponding concrete properties (usually compressive strength). The size of the reinforced concrete element and the quantity of reinforcement to resist bending, shear and torsional forces are determined.
• Serviceability limit state. In this phase of the work, checks are made to ensure the serviceability criteria (i.e. that the building is comfortable to use) are met.

Pre-design

Pre-design stage involves selecting initial section sizes (e.g. reinforcement diameter), from which the minimum required cover depth could be selected to attain the required fire resistance. Although these initial estimates are likely to change throughout the design, giving considerable amount of thought at this stage is likely to save a lot of time later on.

Ultimate limit state

Ultimate limit states are often more critical for concrete structures. Consequently when design is undertaken, the ultimate limit state is designed for and then if necessary serviceability is checked for. However, element sizes ascertained in the pre-design stage usually ensure serviceability criteria are met.

Serviceability limit state

Serviceability requirements to check for deflection and crack widths are generally satisfied by observing the following details.

• Checking and keeping within permitted span/effective depth ratios
• Providing not less than the minimum permitted percentage of reinforcement.
• Limiting the spacing of tension reinforcement.
• Using “deemed to satisfy” empirical methods.

If actual deflections are required, then the structure must be analysed for the serviceability limit state, using design service loads. The deflections obtained will generally be short term values and will be multiplied by a suitable factor to allow for creep effects and to give realistic long term values.

Contents

1. General
2. Basis of design
3. Materials (concrete and steel) including
   1. Concrete
   2. Reinforcing steel
   3. Prestressing steel
4. Durability and cover to reinforcement
5. Structural analysis
6. Ultimate limit states
7. Serviceability limit states
8. Detailing reinforcement and prestressing tendons
9. Detailing members, and particular rules
10. Precast elements - additional rules
11. Lightweight aggregated concrete structures
12. Plain and lightly reinforced concrete structures

External links

• Information about Eurocode 2