Concrete is a non-combustible material and has a slow rate of heat transfer. For these reasons, most designers commonly perceive that concrete members do not require any additional protection because of its built-in resistance to fire. A prescriptive concrete fire design consists of specifying minimum geometric sizes and covers to all reinforcement for concrete members. By following these simple rules, designers will generally assume that the fire resistance will be achieved and will give no further thought to the fire design. In UK, designers seldom venture beyond BS8110-1 (1997) when checking the fire resistance of concrete members. BS8110-2 (1985) –Code of practice for special circumstances, which provides more guidance on achieving the required fire resistance, is usually only used when an error is made during construction relating to the cover, or when lightweight concrete is used.

Concrete buildings are commonly perceived to have sufficient fire resistance.

The typical prescriptive approach for concrete fire design gives tabular data specifying the minimum dimensions, and concrete covers to reinforcement, for various types of concrete members for a given standard fire resistance period. The minimum covers are normally derived to ensure that the temperature of reinforcement does not exceed a specified critical temperature. Different considerations may be made for distinguishing normal weight and lightweight concretes, siliceous and calcareous aggregates, support conditions and loading levels.

The tabular data from BS8110-2 (1985) and EN1992-1-2 (2003) are discussed below.

Tabulated Data

BS8110-2 is based on the information and tabular data contained in a Building Research Establishment Report published by the Department of the Environment (Morris et al. 1988). The tabular data are derived from standard fire resistance test data mainly conducted in the 1950¡¯s. BS8110-2 partially removes the conservatism in the prescriptive rules given in Part 1 of BS8110 by specifying cover to main bars. The tabular method may be used when no relevant test result is available from a laboratory that has carried out a test in accordance with BS476-20 (formerly Part 8).

Similarly, the tabular data of EN1992-1-2 have been developed on an empirical basis validated by experience and theoretical evaluation of tests. Compared with those of BS8110-2, the tabular data of EN1992-1-2 are more comprehensive.

In the following table, the main characteristics of the tabular data of both BS8110-2 and EN1992-1-2 are briefly discussed and compared.