EVALUATION OF FIRE PROTECTIVE PROPERTIES OF COATINGS AND FACINGS FOR STEEL STRUCTURES

Abstract

When developing a new or upgrading an existing formulation (composition) of fire protective materials intended for coating or facing steel structures, the use of European methods set out in EN 13381-4: 2013 and EN 13381-8: 2013 is not acceptable for economic reasons. These reasons are related to the significant cost and duration of fire tests, as well as the need to use a large amount of fire protective material in the design of test specimens. For these purposes, it is advisable to conduct tests that require much lower costs.

The conducted research aimed to substantiate the method of evaluation of fire protective properties of coatings and facings for steel structures, acceptable for use at the stage of their development or modification of their formulation (composition). Its components and procedures are defined, which allow to carry out such assessment at much lower test costs compared to the European methods.

The suggested method has experimental and computational components. In the experimental part, the temperature of samples of steel structures equipped with fire protection with the same thickness and different formulation of the coating is measured under fire conditions at standard temperature regime. For the manufacture of these samples square steel plates 5 mm thick with a side of 500 mm, insulated from their unheated surface, were used. Based on fire test results, the basic sample with the best fire protective properties was determined.

Time interval t_D required to reach the design temperature in the range from 350 °C to 600 °C with 50 °C steps was determined for both basic and additional test samples. The obtained data are approximated with respect to the time interval t_D, using the numerical linear regression equation, which establishes the relationship between the time interval of reaching the design temperature and the thickness of the fire protective coating. According to the obtained values of regression coefficients the predicted value of coating or facing thickness, which provides a normalized class of fire resistance of the steel structure (column, beam), can be determined if necessary.

This method was used to evaluate fire protective properties of the coating based on "Thermodon TOP" formulation (at the stage of its development). According to the results of this evaluation, the most effective composition of the formulation, as well as the relationship between the time of reaching the design temperature and fire protective coating thickness was determined and the predicted values of coating thickness for normalized fire resistance classes of steel structures were calculated.

The directions of further researches were defined: they would focus on revealing the influence of a geometrical form of sample steel structures with coatings and facings on the results of fire protective properties evaluation.