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This study aims to propose a new design value, based on experimental and numerical studies, for surface emissivity of zinc hot-dip galvanized members exposed to fire.

The paper sums up experiments, used specimens and also shows results. Four experiments were performed in a horizontal furnace and one test in a fire compartment of the experimental building. Several tests were carried out for determination of the surface emissivity of galvanized steel structures in fire. The experimental and numerical studies were used for preparation of new generation of the structural steel fire standard Eurocode EN 1993-1-2:2025.

Hot-dip galvanizing is one of the most widely used processes for corrosion protection of steel products. The new design value for surface emissivity of zinc hot-dip galvanized members exposed to fire is determined using experimental results as 0.35. The value is proposed for next generation of EN 1993-1-2:2025. If hot-dip galvanization additionally can contribute beneficially to the fire resistance of unprotected steel members, it would be a huge economic advantage.

Experimental studies in the past years have indicated the influence of hot-dip galvanizing on the heating of steel members. This study suggests 50% reduction of the surface emissivity of a carbon steel member. This amendment will be incorporated in future versions of Eurocodes 3 and 4 and has already been implemented in some fire design tools for steel members in order to consider the beneficial contribution of hot-dip galvanized for fire-resistance requirements of less than 60 min.

The main results from a numerical investigation on a composite floor made of cellular beams at elevated temperatures are presented. From a full-scale natural fire test, a 3D finite element model has been developed under ANSYS code to simulate the thermo-mechanical behaviour of a composite floor with cellular beams. The calibration of this numerical model is based on the measured material properties and temperatures. A good correlation between the test and the numerical simulation is observed, in terms of temperatures, deformed shape and deflections. The finite element model is then used in a parametric study varying bay size, mechanical load and fire resistance rate. The results from this parametric study are compared to those from an analytical method, highlighting the conservativeness of the latter.