Concrete @ your Fingertips

Design working life

BS EN 1990, Eurocode - Basis of structural design, (Eurocode 0) gives indicative design working lives (in Table 2.1) for design purposes for various types of structures, as follows:

Category 1 Temporary structures, not including structures or parts of structures that can be dismantled with a view to being re-used 10 years
Category 2 Replaceable structural parts, e.g. gantry girders, bearings 10 to 25 years
Category 3 Agricultural and similar buildings 15 to 30 years
Category 4 Building structures and other common structures 50 years
Category 5 Monumental building structures, bridges and other civil engineering structures 100 years

It should be noted that the UK National Annex to BS EN 1990:2002 gives modified indicative design working lives for some of the Categories as follows:

Category 2 10 to 30 years
Category 3 15 to 25 years
Category  5  120 years

Presumably the Category 5 change to 120 years was to bring the recommendations into line with the requirements of the Highways Agency (now Highways England). This was covered in  IAN 95, although this has now been withdrawn as Highways England now refer to BS 8500-1 Concrete for limiting constituents for durability i.e. based on at least 50 or 100 years intended working life. See Manual of Contract Documents for Highway Works (MCHW), Vol. 1, Specification for Highway Works, Series 1700

Prior to the introduction of the Eurocode a design life of 60 years was required for buildings, though this period was never included in any of the structural design Codes. For concrete bridges up until 1978, it had always been a 100 year design life. 100 years does not appear to be explicitly included in prior codes, just seems to be an expectation for that type of structure. The design life figure went up to 120 years with the introduction of BS 5400 Part 2 in 1978 and BS 5400 Part 4 in 1984.