Eurocode FAQs
1. What are the Eurocode equivalents of BS 8110-1, BS 8110-2, BS 8007, BS 5400, BS 8102, CIRIA 139?
BS EN 1992-1-1 and BS EN 1992-1-2 replaced BS 8110-1 and BS 8110-2.
BS EN 1992-2 replaced BS 5400-4, but note that BS EN 1992-2 has to be used in conjunction with BS EN 1992-1-1.
BS EN 1992-3 replaces BS 8007, but note that BS EN 1992-3 has to be used in conjunction with BS EN 1992-1-1.
BS 8102 was revised in 2009.
CIRIA 139 is a guidance document on the design of basements. It has largely been superseded by BS EN 1992-3, which should be used together with CIRIA C660 (Early thermal cracking). See Concrete Basements.
2. When will I have to change from using BS 8110/BS 5400 to using Eurocode 2?
Although Eurocode 2 replaced all previous national codes dealing with the design of structural concrete, there continues to be a period of transition. Previous British Standards such as BS 8110, BS 8007 continue to be used but were ‘withdrawn’ in 2010, i.e. they are no longer supported by the relevant British Standards Institute committee. BS 8110 is not necessarily unsafe, but will increasingly become outdated and therefore not current best practice.
For bridges, the major clients are public bodies and under European law they should require designers to use Eurocodes from March 2010 for new contracts. For buildings there is no obligation to use Eurocode 2 from this date as the building regulations only require that the designer shows that design is safe; there is no obligation to use a particular Code of Practice. Clients (particularly those which are public bodies) or a designer’s insurers may require the latest Codes of Practice to be used, this will be a driver to change over to Eurocodes.
3. What is the minimum number of bars in a circular column?
Eurocode 2 has a minimum number of 4 (BS 8110 recommends 6). If only using 4 bars use any column design charts with caution because they may have assumed a minimum of 6 bars.
4. In Eurocode 2, is the lap length based on the size of the smaller bar as is the case to BS 8110.
Eurocode 2 is not specific, but logically the strength of the lap will be limited by the smaller bar and therefore this should be used to determine the minimum lap length.
5. What is the relationship between cylinder strength and cube strength? And is it the same for lightweight concrete?
There is no single expression linking cylinder strengths to cube strengths in Eurocode 2, but they are given in Table 3.1 of BS EN 1992-1-1 for normal weight concrete and roughly speaking the cylinder strength is 80% of the cube strength. For lightweight concrete, the information is given in Table 11.3.1 and roughly speaking the cylinder strength is 90% of the cube strength.
6. What angle of the concrete strut should I take in assessing the shear strength to Eurocode 2 as it is not set at 45 degrees?
Generally, it will be found that a strut angle of 21.8° provides adequate strength and it is therefore advised to assume this in the first instance.
For heavily loaded and transfer beams the strut angle may need to be increase and the angle required can be calculated. Further guidance is given under Shear and in How to design concrete structures using Eurocode 2: Chapter 4, Beams.
7. Are there any worked examples for design to Eurocode 2?
Yes. Worked Examples by The Concrete Centre are available in the Publications Library, and some are included within this section of the site.
A set of examples has also been published by British Precast for precast concrete elements, including prestressed elements.
Other worked examples include:
from JRC - http://eurocodes.jrc.ec.europa.eu/doc/1110_WS_EC2/report/1110_WS_EC2.pdf
and from ERMCO: http://www.ermco.eu/documents/ermco-documents/worked-examples-ec2-def080723.pdf
8. Where do I find a list of the new symbols and abbreviations used in Eurocode 2?
Each Eurocode has a list of symbols in section 1. The symbols are also usually described in full at the point at which they are introduced. A comprehensive list of symbols can be found at the front of Concise Eurocode 2 and Concise Eurocode 2 for bridges. (Note, they are slightly different lists to suit buildings and bridges respectively.)
9. What load case should I take when designing for cracking in prestressed concrete?
The frequent load combination should be used.
10. Can I design for the shear force at d away from the support in Eurocode 2?
Yes, providing the load is predominately a udl. See clause 6.2.1(8) of BS EN 1992-1-1.
11. How do I work out the appropriate concrete cover?
Concrete cover is required for three reasons:
1. For bond - use bar diameter for reinforced concrete. See clause 4.4.1.2(3) for prestressed concrete.
2. For durability – use BS 8500.
3. For fire resistance – use BS EN 1992-1-2, section 5. Fire resistance works on ‘axis distance’ to the centre of the main bars - cover has to be calculated from there.
An allowance for deviation (usually 10 mm) is added to the maximum cover required from 1 to 3 above to obtain the nominal cover, cnom.
Further guidance is given in How to design concrete structures using Eurocode 2: Chapter 2, Getting Started.
12. How have you derived the formulae for K and K'?
We have worked from first principles see Flexure
13. How do I work out the slenderness limit for a column to Eurocode 2?
A column is slender if l > llim
Slenderness, l = lo/i = 3.46l0/h for rectangular columns
Limiting slenderness llim = 20ABC/n0.5
Where
lo = effective length (=1.0l for pinned ends, generally = approx. 0.75l for rotationally restrained ends)
i = radius of gyration
h = minimum dimension of rectangular column
A = an allowance for creep, default value 0.7
B = an allowance for the ‘mechanical ratio’ default value 1.1
C = an allowance for moment distribution, default value 0.7 but that is onerous and a value of approx. 2.5 might be obtained by rudimentary calculation.
n = axial load / area of the concrete
A procedure for working through the guidance can be found in How to design concrete structures using Eurocode 2, chapter 5, columns. It is dealt with in BS EN 1992-1-1 Section 5.8.3.
14. Is there a maximum limit for horizontal deflection to Eurocode 2?
There is no guidance given in Eurocode 2.
15. Can I enhance the shear capacity of a section close to the support in Eurocode 2?
Clause 6.2.2(6) of BS EN 1992-1-1 explains how the shear from a concentrated load close to the support can be reduced to take into account direct strutting action to the support. The attendant rules for shear links can be more conservative than ignoring this ‘enhancement’. For bridges, the UK National Annex to BS EN 1992-2 amends this clause so that is the shear resistance is enhanced.