FIRE RESISTANCE OF REINFORCED CONCRETE AND STEEL STRUCTURES

The scientific bases of ensuring fire resistance of reinforced concrete and steel building structures in the conditions of modern extreme influences are laid. The current state of fire safety of buildings and structures, as well as approaches, methods and tools for its assessment are analyzed. Analysis of emergencies and fires in the world has shown that the vast majority of them occur in buildings and structures. It is shown that the cause of catastrophic consequences and destruction is the non-compliance of the actual limit of fire resistance of building structures with regulatory requirements. This is due to the imperfection of methods and means of assessing the fire resistance of building structures, including fire-retardant. To overcome the shortcomings identified during the analysis, the paper develops physical and mathematical models of thermal processes occurring in the fire-retardant reinforced concrete structure. Based on the proposed models, a computational-experimental method for estimating the fire resistance of such structures has been developed. The efficiency of the proposed method was tested by identifying the relationship between the parameters of the fire-retardant plaster coating “Neospray” and the fire resistance of fire-retardant multi-hollow reinforced concrete floor. The study of fire resistance of steel structures is proposed to be carried out using reduced samples in the form of steel plates with dimensions of 500×500×5 mm. Based on the proposed models, a calculation and experimental method for estimating the fire resistance of steel structures, as well as an algorithm and procedures for its implementation have been developed. The verification of the efficiency of the proposed method was carried out in the ANSYS software package using the aged coating “Phoenix STS” and the coating “Amotherm Steel Wb” under heating conditions at the temperature of the hydrocarbon fire. The reliability of the developed models and methods is checked. It is established that random errors in temperature measurement significantly affect the accuracy of determining the thermophysical characteristics and limits of fire resistance. In general, the efficiency of the proposed calculation and experimental methods with sufficient accuracy for engineering calculations is confirmed

Construction of A Method for Detecting Arbitrary Hazard Pollutants in the Atmospheric Air Based on the Structural Function of the Current Pollutant Concentrations

This paper reports the construction of a method for calculating the structural function within a moving window of the fixed size, based on measuring the vector of current concentrations of arbitrary air pollutants. The use of a moving window makes it possible to reveal the current moments of the emergence of inhomogeneities in the polluted atmosphere. In this case, the time shift of the structural function reveals the corresponding time scale of this heterogeneity. It has been shown that, in contrast to the known method, the proposed method makes it possible to reveal the dynamics of the levels and scales of local inhomogeneities of the polluted air using only the current measurements of concentration for an arbitrary number of pollutants. It is noted that the method does not use information about the current meteorological conditions of the atmosphere and the features of urban infrastructure near a pollution control point. Therefore, the method is universal; it could be applied to arbitrary control points of atmospheric pollution across various territories of states. The efficiency of the proposed method was tested using the example of actual measurements of the concentrations of urban air pollutants involving formaldehyde, ammonia, and nitrogen dioxide. The reported results generally indicate the applicability of the proposed method. It has been experimentally established that the method makes it possible to identify, in real time, the areas of local inhomogeneities characteristic of hazardous air pollution associated with the absence of dispersion and accumulation of pollutants in the air. In addition, the method makes it possible to detect in real time both the levels and the scale of inhomogeneities in the polluted atmosphere. It has been experimentally established that before the occurrence of the tested reliable emergency in a polluted atmosphere, the level of local heterogeneity was 0.015 units at its time scale corresponding to 8 counts. Next, by the time of the emergency, the level of heterogeneity decreased to 0.0025 units at the time scale corresponding to 2 counts. It has been experimentally established that for this case the forecast time of the occurrence of an emergency was 4 counts or 24 hour

Construction of A Method for Detecting Arbitrary Hazard Pollutants in the Atmospheric Air Based on the Structural Function of the Current Pollutant Concentrations

This paper reports the construction of a method for calculating the structural function within a moving window of the fixed size, based on measuring the vector of current concentrations of arbitrary air pollutants. The use of a moving window makes it possible to reveal the current moments of the emergence of inhomogeneities in the polluted atmosphere. In this case, the time shift of the structural function reveals the corresponding time scale of this heterogeneity. It has been shown that, in contrast to the known method, the proposed method makes it possible to reveal the dynamics of the levels and scales of local inhomogeneities of the polluted air using only the current measurements of concentration for an arbitrary number of pollutants. It is noted that the method does not use information about the current meteorological conditions of the atmosphere and the features of urban infrastructure near a pollution control point. Therefore, the method is universal; it could be applied to arbitrary control points of atmospheric pollution across various territories of states. The efficiency of the proposed method was tested using the example of actual measurements of the concentrations of urban air pollutants involving formaldehyde, ammonia, and nitrogen dioxide. The reported results generally indicate the applicability of the proposed method. It has been experimentally established that the method makes it possible to identify, in real time, the areas of local inhomogeneities characteristic of hazardous air pollution associated with the absence of dispersion and accumulation of pollutants in the air. In addition, the method makes it possible to detect in real time both the levels and the scale of inhomogeneities in the polluted atmosphere. It has been experimentally established that before the occurrence of the tested reliable emergency in a polluted atmosphere, the level of local heterogeneity was 0.015 units at its time scale corresponding to 8 counts. Next, by the time of the emergency, the level of heterogeneity decreased to 0.0025 units at the time scale corresponding to 2 counts. It has been experimentally established that for this case the forecast time of the occurrence of an emergency was 4 counts or 24 hour