THE RESEARCH OF THE FIRE RESISTANCE LIMITS OF A REINFORCED CONCRETE SLAB ACCORDING TO THE RESULTS OF FIRE TESTS WITHOUT MECHANICAL LOAD

The paper analyzes the thermal effect of fire on reinforced concrete slabs based on their heating according to the standard fire temperature regime in a small-sized installation for the study of the thermal effect of fire on building structures. On the basis of the proposed method, a methodology was created that makes it possible to obtain data on temperature distributions on the surfaces of a slab fragment and in its cross-section. The course and results of the conducted fire test are described, and the adequacy and reproducibility of the experimental data are verified. The temperature distribution over the entire area of the fire furnace, the studied fragments, was analyzed and the obtained results were processed. The possibility of creating a standard fire temperature regime in the fire furnace chamber has been verified. According to the results of this work, it was established that during the heating of reinforced concrete, the release of moisture and steam inside the material was observed: on the heated surface, this process took place from 15 to 25 minutes, on the unheated surface from 39 to 57 minutes, and at the level of the reinforcement from 31 to 55 minutes, the heating of the structure at all levels was uniform in the planes of placement of thermocouples, the maximum temperature at the level of the reinforcement was 200 degrees C, it was observed in the last minute of the experiment and continued to increase linearly after leaving the plateau, the maximum temperature on the unheated surface of the rock was 110 degrees C, it observed at the last minute of the experiment and continued to grow linearly after leaving the plateau. The adequacy of the experimental data was confirmed: the relative deviation did not exceed 4%, and the calculated adequacy criteria (Fisher, Student and Cochrane) were below the critical value.