Approach for modelling the galvanization effect on steel structures in fire

This paper presents the main results of an experimental program aimed at the investigation of the behaviour of galvanized steel members and the characterization of its surface emissivity starting from the temperatures measured during small-scale furnace tests. The results confirm the beneficial effect of galvanization on slowing down the heating, indeed, the temperatures in the hot dip galvanized specimens were found lower than the not galvanized ones. Tests results also confirm that the emissivity depends on steel temperature, in line with the new Eurocode. Considering the effect of hot-dip galvanizing by implementing a variable emissivity, allows for the extension of calculation methodologies for the fire resistance of steel elements, even for galvanized steel, using both simplified and advanced methods. Therefore, this paper presents results of several implementations of the Eurocode design methods for assessing the structural fire resistance of galvanised steel elements. In this framework, the simplified "nomogram procedure" approach, typically used for steel members, has been adjusted by authors for galvanized steel elements. Finally, the results of advanced thermo-mechanical analyses of steel single story frames, which were carried out to assess the effect of the galvanization on the whole structural fire behaviour were reported. This latter shows that, also in this case, if the required performance level is not particularly severe, the galvanization allows to guarantee the fire requirements, saving the application of fire protection.