Fire performance of a steel open car park in the light of the recent development of the localised fire model "LOCAFI"

The paper presents the results of a comprehensive finite element thermo-mechanical analysis conducted on a steel open car park subjected to localised fires. In particular, the LOCAFI model, a localised fire model recently developed in a European research project to estimate the radiative heat flux received by vertical members, was exploited to evaluate the fire performance of bare steel columns under the typical fire scenario of 4 vehicles burning around a column. The car park, to be built in Italy, was designed according to the Italian Building Code and the Eurocodes with steel grade S460M. Different column profiles were selected in order to optimise the structural fire performance, structural weight and related costs. The parametric analysis showed that, for this fire scenario and the selected profiles, the LOCAFI model was not the major governing factor of the column collapse. Indeed, when collapse occurred, it was mainly caused by material fracture in the column element just below the slab and subjected to the Hasemi model. As a result, it was observed that cross sections with thicker flanges and webs, i.e. HE of the M series are to be preferred with respect to cross sections with same area but higher inertia such as HE of the B series, that are characterised by thinner flanges and webs. Finally, no composite action and fireproofing are potentially needed for the vertical members by accounting for a profile with an adequate low section factor and higher strength, e.g. in this specific case an HE 260 M series S460M quality.