ADJUSTING THE TIME INTERVAL UNTIL THE CRITICAL TEMPERATURE IS REACHED FOR TEST SAMPLES OF PROTECTED STEEL STRUCTURES

Abstract

To evaluate the resistance to external environmental influences (water, humidity, ultraviolet radiation and air temperature) of reactive and passive fire protection systems intended for load-bearing steel structures, the test method described in EN 16623 and EAD 350140-00-1106 is used. This fire test determines the time interval from the beginning of the fire exposure at a standard temperature until the critical steel temperature of 500 °C is reached on the metal surface of four test specimens made in the form of 5 mm thick steel plates with the same fire protection thickness. Based on the results of comparing the experimental data obtained for the two exposed samples and the two control samples, a conclusion is made about the resistance to external influences. Differences in the temperature regime in the furnace, the thickness of the fire protection and the initial temperature of the test samples may lead to certain errors in the results of the assessment of this resistance.

The study revealed regularities in the influence of the non-uniformity of the initial temperature of the test samples on the results of assessing the fire protection resistance of steel structures to external environmental influences. It was found that the difference between the time intervals until the critical steel temperature of 500 °C was reached, obtained for test specimens with different initial temperatures, depends on the difference between the initial temperatures of these specimens and the value of this time interval and does not depend on the thermal properties of the fire protection material. This difference increases with the difference between the initial temperatures and the time interval, and its maximum value is 2.69%, which is 17.9% of the limit value used in making decisions on the resistance of fire protection of steel structures to external influences.

A procedure for adjusting the indicators of the time interval until the critical temperature of 500 °C is proposed, which allows eliminating the effects of the uneven initial temperature of test samples on the results of assessing the fire protection resistance of steel structures to external environmental influences.