Журавський Максим Миколайович
@nuczu.edu.ua
Національний університет цивільного захисту України
Scopus Publications
Scopus Publications
Ivan Nesen, Stanislav Sidnei, Olena Petukhova, Maxim Zhuravskij, and Eugene Tishchenko
Private Company Technology Center
This paper reports the analysis of fire resistance assessment methods of building structures. Based on the results, it was established that conducting fire tests is not expedient and harmful to the environment. The use of estimation fire resistance assessment methods for reinforced concrete staircases is not considered possible due to the lack of appropriate tables with fire resistance classes for the tabular method. The use of the estimation zone method is also impossible because of the lack of temperature nomograms of temperature distribution during exposure to the standard fire temperature regime. There are also no described procedures for applying the estimation refined method for reinforced concrete staircases. So, using mathematical models, the existing type of reinforced concrete staircase was reproduced. Employing the finite-element method, the behavior of reinforced concrete stairwells under the influence of fire was investigated. Based on the results of these experiments, it was analyzed which structural geometric parameters of reinforced concrete stairwells have the greatest influence on their fire resistance. In this way, three independent, most significant geometric parameters of reinforced concrete stairwells were established – the height of the solid base, the thickness of the protective layer of the lower row of reinforcing bars, and the length of the span. Therefore, the ranges of the most significant structural geometric parameters of reinforced concrete stairwells were used to build a regression dependence of the fire resistance limit on these parameters in order to design a full factorial numerical experiment. After proving the adequacy of the results obtained according to the regression dependence, tables were constructed with the geometric parameters of reinforced concrete stairwells to determine the compliance of these structures with the required fire resistance class. The use of these tables will make it possible to reduce the risks of threats to human life and health during a fire by determining the possibility of using these structures with a guaranteed fire resistance class during design
Boris Pospelov, Vladimir Andronov, Evgenіy Rybka, Olekcii Krainiukov, Nadiya Maksymenko, Igor Biryukov, Maxim Zhuravskij, Yuliia Bezuhla, Ihor Morozov, and Ihor Yevtushenko
Private Company Technology Center
A self-adjusting zero-order Brown’s model has been devised. This model makes it possible to predict with high accuracy not only fires in the premises but also irreversible processes and phenomena of a random and chaotic nature under actual conditions. The essence of the self-adjusting model is that, based on Kalman’s approach, it is proposed to set the smoothing parameter for each time moment. Such a parameter is determined depending on the resulting current forecast error, taking into consideration the real and unknown dynamics of the studied series and noise. That does not require the selection of the smoothing parameter characteristic of known models. In addition, the proposed Brown’s model, unlike the known modifications, does not require setting a dynamics model of the level of the examined time series. The self-adjusting model provides negligible errors and efficiency of the forecast. The operability of the devised model was checked using an example of the experimental time series for the current measure of the recurrence of the increments of the state of the air medium in the laboratory chamber during alcohol combustion. As quantitative indicators of the quality of the forecast error, the current values for the square and absolute values were considered. It has been established that the current square of the forecast error is more than six orders of magnitude smaller compared to the case of a fixed smoothing parameter from a beyond-the-limit set. However, the current square of the forecast error for abrupt changes in the dynamics of the series level is half that of the fixed parameter of the beyond-the-limit set. It is noted that the results confirm the feasibility of the proposed self-adjusting Brown’s model
Andrii Kovalov, Yurii Otrosh, Oleksandr Chernenko, Maxim Zhuravskij, and Marcin Anszczak
Trans Tech Publications, Ltd.
The results of the experimental determination of temperature from a non-heating surface of steel plates with a fire-protective coating under conditions of fire exposure under the hydrocarbon fire temperature regime are presented. A calculated finite element model of the system “steel plate-flame retardant” was constructed to simulate the non-stationary heating of such a system in the ANSYS R17.1 software complex. The reliability of the numerical simulation results is estimated by real test, the adequacy of the developed model to the real processes occurring when heating the steel plates with fire-protective coating under the conditions of hydrocarbon fire temperature mode is made.
Yurii Otrosh, Yevhen Rybka, Oleksandr Danilin, and Maksym Zhuravskyi
EDP Sciences
There are about 200 operating mines in Ukraine, most of which have not been reconstructed for more than 20 years. Modern anthropogenic and ecological impacts are caused by local technogenic catastrophes and the global ecological crisis. The statistical data on the safety of Ukrainian mines were considered. A literary analysis has been made of advanced expertise in the technical state assessment of the building structures. The purpose of the study is to make optimal decisions when constructing, operating and maintaining the buildings. The procedure for assessing the building state is the result of research, the purpose of which is to develop a technique for reliable and operational assessment of the building structures technical state. In this paper, a technique is proposed for inspecting the constructions and assessing their technical state. The maximum efforts in elements of the adapted frame were used for checking calculations and constructional design. The obtained calculation results were used in determining the sufficiency of existing cross section value of the structure elements. According to the calculation results, a conclusion has been made that hardness, stability and rigidity of the frame elements as a whole are ensured; further operation of the building structures is possible providing for the project development to strengthen building structures and to implement the design solutions at the construction site. In order to ensure the continued normal operation, it is necessary to develop a project for strengthening the structures, as well as a project for fire protection of building structures.
Leonid Kutsenko, Volodymyr Vanin, Olga Shoman, Leonid Zapolskiy, Petro Yablonskyi, Serhii Vasyliev, Volodymyr Danylenko, Elena Sukharkova, Svitlana Rudenko, and Maxim Zhuravskij
Private Company Technology Center
The study of possibilities of geometric modeling of non-chaotic periodic paths of motion of a load of a swinging spring and its variants has been continued. In literature, a swinging spring is considered as a kind of mathematical pendulum which consists of a point load attached to a massless spring. The second end of the spring is fixed motionless. Pendular oscillations of the spring in a vertical plane are considered in conditions of maintaining straightness of its axis. The searched path of the spring load was modeled using Lagrange second-degree equations. Urgency of the topic is determined by the need to study conditions of dissociation from chaotic oscillations of elements of mechanical structures including springs, namely definition of rational parameter values to provide periodic paths of their oscillations. Swinging springs can be used as mechanical illustrations in the study of complex technological processes of dynamic systems when nonlinearly coupled oscillatory components of the system exchange energy with each other. The obtained results make it possible to add periodic curves as «parameters» in a graphic form to the list of numerical parameters of the swinging spring. That is, to determine numerical values of the parameters that would ensure existence of a predetermined form of the periodic path of motion of the spring load. An example of calculation of the load mass was considered based on the known stiffness of the spring, its length without load, initial conditions of initialization of oscillations as well as (attention!) the form of periodic path of this load. Periodic paths of the load motion for the swinging spring modifications (such as suspension to the movable carriage whose axis coincides with the mathematical pendulum) and two swinging springs with a common moving load and with different mounting points were obtained. The obtained results are illustrated by computer animation of oscillations of corresponding swinging springs and their varieties. The results can be used as a paradigm for studying nonlinear coupled systems as well as for calculation of variants of mechanical devices where springs influence oscillation of their elements and in cases when it is necessary to separate from chaotic motions of loads and provide periodic paths of their motion in technologies using mechanical devices
Leonid Kutsenko, Oleg Semkiv, Andrii Kalynovskyi, Leonid Zapolskiy, Olga Shoman, Gennadii Virchenko, Viacheslav Martynov, Maxim Zhuravskij, Volodymyr Danylenko, and Nelli Ismailova
Private Company Technology Center
Studies of geometric modeling of non-chaotic periodic paths of movement of loads attached to a variety of mathematical pendulums were continued. Pendulum oscillations in a vertical plane of a suspended weightless spring which maintains straightness of its axis were considered. In literature, this type of pendulum is called a swinging spring. The sought path of the load of the swinging spring was modeled with the help of a computer using values of the load weight, stiffness of the spring and its length without load. In addition, initial values of oscillation of the swinging spring were used: initial angle of deviation of the spring axis from the vertical, initial rate of change of this angle as well as initial parameter of the spring elongation and initial rate of elongation change. Calculations were performed using Lagrange equation of the second kind. Variants of finding conditionally periodic paths of movement of a point load attached to a swinging spring with a movable fixing point were considered. Relevance of the topic was determined by necessity of study and improvement of new technological schemes of mechanical devices which include springs, in particular, the study of conditions of detuning from chaotic oscillations of the elements of mechanical structures and determination of rational values of parameters to ensure periodic paths of their oscillation. A method for finding values of a set of parameters for providing a nonchaotic periodic path of a point load attached to a swinging spring was presented. The idea of this method was explained by the example of finding a periodic path of the second load of the double pendulum. Variants of calculations for obtaining periodic paths of load movement for the following set parameters were given: ‒ length of the spring without load and its stiffness at an unknown value of the load weight; ‒ length of the spring without load and the value of the load weight at unknown spring stiffness; ‒ value of the load weight and stiffness of the spring at an unknown length of the spring without load. As an example, determination of the values of a set of parameters to provide a non-chaotic, conditionally periodic path of movement of a point load attached to a swinging spring with a movable attachment point was considered. Phase paths of functions of generalized coordinates (values of angles of deflection of the swinging spring axis from the vertical and extension of the spring) were constructed with the help of which it is possible to estimate ranges of these values and rates of their variation. The results can be used as a paradigm for studying nonlinear coupled systems as well as in calculating variants of mechanical devices where springs affect oscillation of their elements when it is necessary to detune from chaotic movements of loads in the technologies using mechanical devices and provide periodic paths of their movement