General approach for the assessment of the fire vulnerability of existing steel and composite steel-concrete structures

The fire safety of existing structures is very important from the socio-economic point of view and has high social impact for civil, industrial and commercial buildings. The minimum fire resistance of structures is verified through some regulations, drafted to ensure safety for occupants and rescue teams as well as limited structural damage. Fire design rules are not always directly applicable to existing buildings, which need specific provisions to take account of uncertainties on the structural geometry, and the mechanical and thermal properties of the materials. This paper aims to provide guidance about the assessment of structural fire safety of existing buildings during a fire. A possible approach is obtained by integrating the general approach suggested by the Eurocodes for the structural assessment of existing buildings with more specific details concerning the structural fire safety check. The approach focuses on the criteria and the tests required to assess thermal properties and effectiveness of protective materials. The methodology is applied to assess an existing steel building protected with intumescent coating (IC), designed and built about 30 years ago. Applied to assess the existing IC, the procedure also provides data required to design a new protection system with advanced calculation methods according to a performance-based approach.