ANALYTICAL METHOD FOR DESIGN OF FIRE RESISTANCE OF STEEL STRUCTURAL ELEMENTS

The engineering approach in the design of fire prevention allows the engineer to study fire pre-vention solutions that do not meet the requirements of the Rules provided that they ensure the same level of fire safety. To design interventions appropriate to ensure the fire resistance of structures, and in particular for the steel structures, the performance approach of the Rules requires the adoption of prede-fined solutions as a function only of the structural material and the required fire resistance. The performance approach of the Norms, therefore, does not take into account the loads acting on the structural element and the critical temperature, which is the temperature at which the load that can be worn in hot equals the exercise load. Often, during the design phase, some of the requirements of rules are difficult, if not impossible to meet. A practical example is that of a restoration project of a historic building, for which interventions are required non-invasive, reversible and compatible. In this paper it is presented a study that enables you to design interventions appropriate to en-sure the fire resistance of structural elements with an analytical method and, therefore, with an engineering approach. In particular, according to the fire scenario adopted, the analytical method proposed allows to determine the critical temperature of the structural element under study, depending on the working load, the resistant section and solicitation of project. Subsequently, depending on the critical temperature and the required fire resistance, it is possible to design the appropriate fire-fighting interventions.