Perehin A. Improvement of the experimental and calculation method of estimating the fire resistance limit of load-bearing reinforced concrete walls

The idea of the work is to improve the experimental and calculation method of assessing the fire resistance limit of load-bearing reinforced concrete walls to guarantee the normative time of their resistance in case of fire based on fire tests of their small-sized fragments without load, by taking into account the features of one-sided heating of the walls and substantiating the rational placement of points for temperature measurements inside the fragments, as well as taking into account the real dimensions of the structure at the calculation stage. The scientific novelty of the dissertation consists in solving the actual scientific and technical task of increasing the effectiveness of the process of assessing the fire resistance limit of load-bearing reinforced concrete walls through scientific substantiation and the further development of improvements for the experimental and calculation method of its determination, taking into account the characteristics of the materials used during experiments and mechanical load during the calculation process. The following main scientific results were obtained: At the same time, for the first time: - the ways for improvement of the experimental and calculation method of evaluating the fire resistance of full-scale structures of load-bearing walls based on the test of their fragments under the standard fire temperature regime without applying a load are proposed, which made it possible to determine the dimensions of the samples and the methods of installing them in the furnace chamber depending on the dimensions of the installation; - the minimum possible configuration parameters of the furnace chamber and possible deviations in its dimensions, which do not affect the reproducibility of the results of experimental studies on the heating of load-bearing walls are scientifically substantiated; - the possibility of minimizing the number of temperature control points during point measurements along the cross-section of a reinforced concrete wall and their rational location (on the non-heating side, armature and the middle of the cross-section of the studied fragment) is substantiated, which made it possible to reduce the number of measuring equipment in experimental studies on wall heating by 30% due to increasing the reproducibility of experimental data. It has been improved: - an experimental-calculation method for assessing the fire resistance of load-bearing reinforced concrete walls, thanks to the increase in environmental friendliness and economy of research, as well as taking into account the real dimensions of load-bearing wall structures; - computational interpolation algorithms for restoring temperature fields in load-bearing reinforced concrete walls based on temperature indicators in specified places, in the middle of structures during fire tests, are substantiated, which makes it possible to propose a more effective scheme for the location of thermocouples in cross-sections of fragments of load-bearing reinforced concrete walls. The application of experimental and computational methods for determining the real temperature distributions and strength of load-bearing wall materials during the assessment of their fire resistance limit has been further developed.