Кафедра "Теоретична та будівельна механіка"<br>(з 2022 р увійшла до складу кафедри Технічна механіка ДІІТ) (з 2016 року об’єднано каф. "Теоретична механіка" та каф. "Будівельна механіка")

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http://crust.ust.edu.ua/handle/123456789/9307

ENG: Department "Theoretical and Structural Mechanics" "Theoretical Mechanics" and "Structural Mechanics"

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Dynamic Track Irregularities Modeling when Studying Rolling Stock Dynamics
(Kaunas Univ. of Technology, Lithuania, 2019) Bondarenko, Iryna O.; Lunys, O.; Neduzha, Larysa O.; Keršys, Robertas
ENG: Abstract The main purpose of this work is to study the process of transferring forces in the interaction of the rolling stock and the railway track in time. It was considered the wheel set movement on a straight track section without taking into account the rolling stock movements in the horizontal plane caused by the wheel conicity. And it was obtained the dynamic track irregularities depending on the rolling stock speed in the cross section of the railway track when a single force passes over it. Using the wave properties during the force propagation in the trackform elements is allowed to determine the time response of the elements to the force action. First, it allowed to take into account the influence of the state of the trackform elements on the work of the trackform itself and to obtain dynamic track irregularities that take into account both the length inhomogeneity and the depth anisotropy of the trackform. Secondly, it allowed to determine the change in strain in the trackform elements in time.
Influence of Atmospheric Humidity on the Critical Buckling Load of Reinforced Concrete Columns
(World Scientific, 2021) Magalhães, Kaique Moreira Matos; Brasil, Reyolando Manoel Lopes Rebello da Fonseca; Wahrhaftig, Alexandre de Macêdo; Siqueira, Gustavo Henrique; Bondarenko, Iryna O.; Neduzha, Larysa O.
ENG: In this paper, an evaluation of the influence of atmospheric humidity on the critical buckling load of reinforced concrete columns is performed. A particular case consisting of a real, extremely slender reinforced concrete pole was taken for the study. The chosen mathematical procedure for calculating the critical load is based on the Mechanics of Deformable Solids due to variations of structure vibration frequency over time. The rheological behavior of concrete related to creep and shrinkage, which illustrates the time-dependent aspect of the problem, was also considered in the analysis following normative recommendations from the Brazilian Association of Technical Standards (ABNT). In order to evaluate value changes of critical buckling loads, different time instants after loading the structure as well as different relative humidity from 0% to 100%, in 10% increments were considered. According to the selected criteria, it was possible to verify that a higher atmospheric humidity decreases the water transport from the interior out to the exterior surfaces of concrete, hence positively influencing structure stiffness. Therefore, the lowest reduction on critical buckling was 41.9% at 100% relative atmospheric humidity, versus the highest 60.7% at 0% relative humidity. A period of 7500 days after loading the structure was considered in the analysis.
Investigation of the Influence of the Rolling Stock Dynamics on the Intensity of Using the Railway Track Elements
(Дніпровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2019) Bondarenko, Iryna O.; Neduzha, Larysa O.
ENG: Purpose. The main purpose of this work is to research deformability parameters of the railway track under various operating conditions as the initial data for the formation of forced oscillations of rolling stock and the trackform use intensity. Methodology. For the research, an original model of the trackform, described with using the basic concepts of the theory of elasticity and the propagation of elastic waves was developed. Findings. It has been established that the ratio between the intensity of work of elements and the trackform, as criteria for deformability, can be used as the estimated parameters of the functionally safe operation of the track. It can be the basis for the classification of critical track states under which it had to perform work to restore its working capacity in order to ensure the required level of efficiency of use construction during the service life. Originality. Trackform and parameters of the elements of the track superstructure and substructure can be described using the railway tracks deformability behaviour. In the future this conclusion will help to increase the efficiency of the dynamic properties of rolling stock when designing and maintain in readiness the infrastructure while in operation. Practical value. Changes in the regulatory framework of rail transport in recent years provide for the observance of its functional safety, therefore, the question of the need to assess the impact of rolling stock on the way to be regarded as a dynamic process with consideration to the deformability resistance track. This research provides a basis for record of the stiffness of deformation that allows creating the regulatory framework for the functional safety of the railway track in Ukraine.
The Problem of a Lack of Material Behaviour Data For Risk Assessment
(Дніпровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпро, 2020) Bondarenko, Iryna O.; Nеduzha, Larysa O.
ENG: Purpose. The main purpose of this work is to provide theoretical support for the need to expand data on changes in the material behaviour under dynamic loads when railway track risk assessment over time due to railway track elements deformability. Methodology. For the research, an original model of railway track design described using the original method based on the ability of elastic waves to propagate energy of power pulses in space and time, as well as a model describing materials as discrete substances were used. Findings. It has been established that the properties of the material affect the deformability of the elements and the design of the railway track; the main parameter in the study of deformability processes is time; material, as a substance, consists of atoms and molecules, and therefore is not continuous; internal physical processes determine changes in the behaviour of the material of an element. Originality. It has been proposed to develop classifications of changes in the physical properties of materi-als according to the probability of irreversible deformations and the impossibility of deformations, as well as classi-fications of changes in the mechanical properties of materials according to the probability of the defect appearance and changing the material structure. Practical value. The ability to simulate analytically any physical processes occurring inside elements due to the proposed method allows combining the influence of mechanical and physical effects into a single calculation. This enables to assess the probability of appearing defects in elements under certain dynamic loads when assessing the railway track risk over time due to railway track elements deformability.

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