Experimental investigation on galvanized steel elements at elevated temperature

Recent studies showed that hot galvanization can reduce the surface emissivity with abeneficial effect on the steel temperature. Therefore, background documents for next generation of Eurocode suggest considering this effect through a temperature dependant surface emissivity relationship. This paper shows the results of high-temperature small-scale tests, aimed at investigating the galvanization effect on steel plates temperature with variable section factors (A m/V). For each Am/V, both galvanized and blank steel specimens were tested to directly compare the temperatures, by using an input curve with a slower heating rate than ISO834 fire curve. The test results show that the heating in galvanized specimens was slower than the one recorded in blank samples, confirming the galvanization beneficial effect. To quantify this effect and to calibrate the emissivity of galvanized steel, the analytical method to assess steel temperature development, was applied using the temperature recorded in the furnace and in the samples. The surface emissivity was confirmed to be temperature dependant. Some applications of temperature dependant emissivity law were carried out, by varying Am/V and the fire curves, to quantify the galvanization beneficial effect. In particular, the ISO834 fire curve and several parametric fire curves, obtained by varying the opening factor, were considered.