Materials Science Forum Vol. 1006

Abstract: The paper analyzes the scientific work on fire protection, fire resistance, mathematical modeling of fire-proof properties, mathematical planning of experiments. The factors determining the efficiency of fire-proof coating have been determined. The experimental technique for determining fire-proof efficiency as an output parameter was selected. A factor space was constructed, and an experimental plan was drawn up. Experimental studies of the fire-proof effect of the coating based on the xerogel of the gel-forming system at all points of the factor space were carried out. A regression equation was obtained that describes the effect of the qualitative and quantitative composition of the coating on its fire-proof efficiency.

Abstract: In analytical form, formulas are obtained for the amplitude of forced harmonic longitudinal vibrations of reinforced concrete and fiber-reinforced concrete columns with fixed edges. In order to verify the proposed approach, columns were simulated in the ANSYS program and calculated by the finite element method. Analysis of the calculations shows that a significant raise in the amplitude of the forced vibrations is observed only in the region of the first resonant frequency. It has been established that the value of the maximum amplitude of the vibrations of the fiber reinforced concrete column is 16% less than that for a reinforced concrete column.

Abstract: In the paper, the tests have been analysed for fire-resistant quality of the hollow-core reinforced-concrete floors with fire-retardant plaster covering under standard temperature regime of the fire. Using the methodology for determining the characteristics of fire-retardant coatings ability for reinforced-concrete floors, the dependences have been obtained of the fire-retardant coating thickness from the concrete protective layer of a hollow-core reinforced-concrete floor for a fire resistance limit of 180 minutes with a temperature regime of hydrocarbon fire and a tunnel curve according to the Netherlands standards (RWS). It has been concluded about the minimum required thickness of the studied fire-retardant coating to provide the required fire resistance limit of a hollow-core reinforced-concrete floor under the indicated fire regimes.

Abstract: Based on analysis of appropriate literary sources we established that estimation of fire separation distances was based of two criteria: heat flux and temperature. We proposed to use “ignition temperature of materials” as principal criterion when determining fire separation distances between adjacent construction facilities. Based on the results derived while performing complete factorial we created mathematical model to describe trend of changing fire separation distances depending on caloric power of fire load (Q), openings factor of the external enclosing structures (k) and duration of irradiation (t); moreover, its adequacy was confirmed. Based on linear regression equations we substantiated calculation and tabular method for the determination of fire separation distances for a facility being irradiated which contains combustible or otherwise non-combustible façade and a facility where liquid oil products turn. We developed and proposed general methodology for estimation of fire separation distances between construction facilities by calculation.

Abstract: The results of experimental studies of the impact strength of samples of concrete and steel fiber concrete are presented. For dispersed reinforcement, three types of steel fiber were used - with bent ends, wave and flattened. Tests were conducted to determine the static and dynamic bending strength, and then - impact tests on the pendulum headstock MK-30. It was found that the impact strength increases significantly in the presence of fiber, but the type of fiber has almost no effect on it. Since specimens reinforced with a fiber content of 1.0 and 1.5% differ slightly in impact strength, 1.0% dispersed reinforcement in volume is recommended, both under static and dynamic loads.

Abstract: There was researched the influence of fire temperature regimes, obtained by the proposed mathematical models, on the mechanical characteristics of metal structures. As a result, the identified patterns of the influence of the parameters of the premises with fires are shown as the slit coefficient decreases and the fire load density increases, the actual limit of fire resistance begins to decrease, as well as at values of fire load density less than 600 [MJ/m²], there is an area where the occurrence of a boundary state is not observed and Nomograms for determining the limit of fire resistance for steel structures at standard values of critical temperature were constructed and an appropriate method was developed.

Abstract: The main aims of this study are to assess numerically the mitigation effects caused by the solid wall installed at the fueling station in order to protect personnel from the consequences of the emergent gas explosion, evaluate the optimal location of the wall and choose the appropriate material the wall have to be made of in order not to be destructed. A three-dimensional mathematical model of an explosion of hydrogen-air cloud is used. A computer technology how to define the personnel damage probability fields on the basis of probit analysis of the explosion wave is developed. The mathematical model takes into account the complex terrain and three-dimensional non-stationary nature of the shock wave propagation process. The model allows obtaining time-spatial distribution of damaging factors (overpressure in the shock wave front and the compression phase impulse) required to determine the three-dimensional non-stationary damage probability fields based on probit analysis. The developed computer technology allows to carry out an automated analysis of the safety situation at the fueling station and to conduct a comparative analysis of the effectiveness of different types of material the protective facilities made of.

Abstract: The known methods of calculation of oscillation amplitudes of massive foundations of machines taking into account damage are analyzed in the article. It is established that the method set out in the building codes allows to determine the amplitudes of the foundation oscillations at any point of the foundation, approximately enough. This technique does not take into account the interaction with the soil of the deepened foundations, but takes into account only the physical and mechanical characteristics under the sole of the foundation. The authors propose a finite element method (FEM) calculation using the Plaxis 7 software package installed on a personal computer and a vibrometer. The result is the oscillation amplitude of the massive foundation. The presence of cracks and damage increases the magnitude of the oscillation amplitudes from the dynamic impact. If you make timely planned repairs to the foundations, the amplitude of the oscillations can be reduced.

Abstract: The article deals with the assessment problems of especially essential structures. Increased demands on prevention of emergency situations and minimizing the consequences in the event of their occurrence require constant determination of especially essential structures condition. Achieving the goal of reliability and continuity of information is possible by coating the structure surface by a layer of electroconductive concrete, working as a monitoring system sensor. The study of the electrical properties of concrete was performed using the voltmeter – ammeter scheme. After the measurements had been made, the conditional electrical resistance of the electrode pair was calculated. The analysis of the above dependencies found that the change in the electrical resistance of the material from its stress approaches the linear law at lower values of W/C over a larger section of the studied interval. Processing of the obtained data showed that the measurement results were significantly affected by the shape and size of the electrodes used during the experiments.

Abstract: The basic problems of the theory such as principle of assigning classes of fire resistance, reliability issues, alternative approach to calculation methods, mathematical models of concrete and reinforcement deformation diagram, numerical modelling techniques, temperature analysis and calculation of mechanical work of structural system in fire conditions have been considered. It is revealed that the real practical problem is the lack of professional training of civil engineers in Ukraine and abroad.