Fire design strategy in permanent tunnel linings (secondary linings)

The design of sprayed concrete and cast in situ linings, with both SFRC (steel fibre reinforced concrete) and RC (reinforced concrete), against fire load as an accidental situation, is included into the Crossrail C121 contract that has been undertaken by Mott MacDonald. The C121 contract is basically described as the engineering services for the SCL structural design of the following underground stations and shafts: Whitechapel Station, Liverpool Street Station, Farringdon Station, Tottenham Court Road Station, Bond Street Station, Eleanor Street Shaft, Stepney Green Shaft and Fisher Street Shaft.

The fire response of steel fibres reinforced concrete (SFRC) and reinforced concrete (RC) members is influenced by the characteristics of constituent materials, namely, concrete, steel fibres and reinforcing steel. These include thermal properties, mechanical properties, deformation properties, and material specific characteristics such as spalling in concrete. The complex behaviour of concrete under this extreme situation leads to a fire design methodology that is based on structural analyses and experimental tests of different liner configurations. Therefore this paper is divided in two main parts: