Vitalii Kovalchuk

The object of research is reinforced concrete sleepers that are subjected to the impact of a wheel in a railroad rolling stock. A procedure is given to theoretically estimate the energy at the impact of a wheel into a reinforced concrete sleeper when a rolling stock wheelset derails. Experimental studies of the geometric parameters of impact traces that occur on reinforced concrete sleepers, depending on the height of the center of mass of the striker above the impact site, were conducted. Based on the results of the experiments, the average geometric parameters of the impact traces were obtained. It was established that the dependence of impact traces on the height of the center of mass of the striker above the place of impact into the reinforced concrete sleeper has a non-linear distribution. Experimental studies of the effect of the location of the reinforced concrete sleeper base on the geometric parameters of impact traces were conducted. It was established that the location of the reinforced concrete sleeper on a solid base and on crushed stone ballast does not exert a significant effect on change in the geometric parameters of impact traces. The obtained experimental values are within the limits of 3σ determined for the rigid abutment of the sleeper. It was established that when testing a reinforced concrete sleeper in a crushed stone box, the amount of energy depends on the height of the striker. At a height of 0.95 m, the amount of energy absorbed by the sleeper together with the ballast was 475 J, and at a height of 1.42 m – 710 J. Analytical dependences were obtained between the length of the face of the impact trace and the amount of absorbed energy, as well as the depth along the direction of the force and the amount of absorbed energy. It was established that the length of the impact trace has an extremum, which does not allow recommending this parameter for estimating the amount of absorbed energy for energy values E<200 J. To determine the amount of energy absorbed by the sleeper, it is recommended to use the parameter of the depth of the impact trace

The object of research is a tunnel conduit made of star-shaped metal corrugated structures. The stresses and magnitude of the plastic hinge occurring in the metal corrugated structures of the tunnel conduit were investigated, taking into account the degree of compaction and the height of the soil backfill. It was established that when the height of the backfill above the tunnel conduit made of precast metal corrugated structures increases and the degree of compaction of the soil backfill decreases, there is an increase in the values of stresses and plastic hinge in metal structures. With the height of the backfill above the conduit equal to 2.75 m and the degree of compaction of the soil backfill RP=80 %, stresses of 235.89 MPa are reached, exceeding the permissible 235 MPa. At the same time, the value of the plastic hinge is 1.03, which exceeds the normative 1.0. It was established that at embankment heights above the tunnel conduit structures from 1.75 m to 2.0 m, the smallest difference in stresses and magnitude of the plastic hinge is observed. At RP=98 %, the stress difference is 0.66 MPa, and the value of the plastic hinge is 0.008. In the case of the height of the embankment above the conduit from 1.5 m to 1.75 m, the stress increase was 5.5 MPa, and the value of the plastic hinge – 0.031. When the embankment height increases from 2.0 m to 2.25 m, the stress difference is 7.57 MPa, and the value of the plastic hinge is 0.041. It was determined that when the height of the embankment above the conduit was increased by 1.0 m in the range from 0.75 m to 1.75 m, the stress difference at RP=98 % increased by 27.84 MPa. However, when the height was increased by 1.0 m in the range from 2.75 m to 3.75 m, the stress difference increased by 12.66 MPa. At the same time, the value of the plastic hinge at embankment heights from 0.75 m to 1.75 m increased by 0.139, and at embankment heights from 2.75 m to 3.75 m – by 0.093

The object of research is the asphalt pavement of road bridges. Its residual period was assessed taking into account the joint effect of the ambient temperature and vehicles. It has been established that a set of negative factors affects the reduction of the service life (residual resource) of asphalt pavement on bridges. These include different modulus of elasticity of reinforced concrete base and asphalt pavement and the difference in coefficients of linear thermal expansion. As well as loads from the wheels of vehicles, temperature fluctuations, alternating freezing-thawing of water in pores and damaged places. It was found that one of the reasons for reducing the residual life of asphalt pavement on reinforced concrete road bridges is the insufficient study and use of polymers in order to adjust the properties of asphalt concrete. Taking into account the joint influence of temperature and transport in assessing the crack resistance of asphalt pavement on reinforced concrete road bridges would allow a more objective assessment of the residual life of such coatings and their service life. Arrangement of asphalt pavement with improved properties, due to polymeric latex, could increase its residual life. This, in turn, would lead to a reduction in costs for the repair and maintenance of not only asphalt pavement but also the road bridge as a whole

The object of this study is the process of determining the dynamic indicators of the pneumatic spring, which is used as the main element of the second stage of spring suspension in the high-speed rolling stock of the railroad, based on the influence of the geometric parameters of the connecting pipeline. It has been established that the dynamic indicators of rolling stock mainly depend on the operation of the pneumatic spring, the characteristics of which are largely determined by the geometric parameters of the connecting element between the pneumatic spring and the additional tank. A mathematical model of oscillations of a dual-mass system has been constructed, the elements of which are connected through a pneumatic spring suspension system. The operation of the pneumatic system is described using the Boyle–Mariotte equations, the state of the ideal gas, the energy for the flow in the connecting pipeline, and the law of conservation of energy. Theoretical studies into the influence of the diameter and length of the connecting element of the pneumatic spring suspension system on energy loss and damping coefficient for the cycle of its operation and the rigidity of the pneumatic spring have been carried out. It was established that the dependence of the stiffness of the pneumatic spring, while changing the value of the diameter of the connecting element from 6 mm to 30 mm, is nonlinear. In the process of compression, the rigidity of the pneumatic spring changes with the length of the connecting element of 1 m from 927 kN/m, static rigidity, to 497 kN/m, dynamic rigidity. The dependences of energy loss and damping coefficient for the operation cycle of the pneumatic spring suspension system based on the hysteresis loop have been constructed. It was found that the difference between the damping coefficient in the process of compression and expansion of the pneumatic spring is no more than 4 %. It was established that the design of high-speed rolling stock is impossible without high-quality modeling of the process of operation of the pneumatic spring suspension system

The object of this study is a reinforced three-layer transport pipe, which is subjected to the joint action of ambient temperature and static loading of the road subgrade soil. The analytical model for assessing the stressed-strained state of reinforced three-layer pipes, under the combined action of temperature and static loads, has been improved using the theory of elasticity. The stressed-strained state of the reinforced pipe was assessed taking into account the values of the joint action of temperature and loads from vehicles, the physical and mechanical parameters of structural materials, and the geometric parameters of the pipe. As a result of the calculation of the reinforced multilayer pipe, it was found that the maximum movements that occur on the outside of the defective pipe are 0.64 mm, the metal pipe – 0.75 mm, and in the concrete mortar (fine-grained concrete) – 0.69 mm. It was established that under the combined action of ambient temperature and static loads from the road subgrade soil, ring stresses are maximum. They are 151 MPa. Axial stresses are also high – 141 MPa. At the same time, the maximum radial stresses are the smallest – 37.4 MPa. It has been established that a small difference in displacements occurs on the contact of structural materials of the reinforced pipe. However, the magnitude of the stresses is high. The maximum difference in ring stresses was 73 MPa, while the difference in radial and axial stresses was up to 1.0 MPa. It has been established that to restore the bearing capacity of damaged reinforced concrete pipes, it is possible to use the repair technology by the method of "sleeving". It involves pulling a metal pipe into the middle of the layer damaged with concrete mortar remaining between the concrete defective and the new metal pipes.

The object of this study is a concrete pipe and a pipe whose integrity was restored using a metal clamp while filling the layer between the existing pipe and the metal clamp with self-expanding concrete mortar. It has been established that the most common types of defects and damage to pipes on the roads are transverse and longitudinal cracks, as well as concrete chipping and spalling. A procedure has been devised to test experimentally a new concrete pipe without reinforcement and a concrete pipe reinforced with a metal clamp under static load. Experimental tests of the concrete pipe without reinforcement and with reinforcement with a metal clamp were carried out in the laboratory. Digital indicators, an analog-to-digital converter, and a personal computer were used to measure pipe deformations. It was found that the maximum value of vertical deformations of a new concrete pipe before cracking was 4.75 mm, and that reinforced by a metal clamp – 4.36 mm. At the same time, the maximum deformation at which the destruction of the new pipe occurred was 6.36 mm, and that of the reinforced pipe with a metal clamp – 10.51 mm. It was established that the reinforcement of the destroyed pipe with a metal clamp in the initial period of loading leads to detachment of the clamp from the concrete of the pipe. Further, when the clamps are included in the work, there is a stable operation of the concrete pipe and the amount of growth of pipe deformations increases smoothly. The results of measuring vertical deformations at the top of the pipe without reinforcement and with it showed different deformation values. It was established that the complete destruction of the pipe with a reinforced metal clamp takes place during deformations 61 % higher than the deformation at which the non-reinforced new concrete pipe is destroyed. It was found that one of the methods of restoring the bearing capacity of damaged and defective pipes in the road industry is the use of metal clamps

This paper reports the analysis of prospects for the use of prefabricated metal corrugated structures in the body of the embankment of a railroad track in the form of a tunnel overpass in order to pass road vehicles and railroad rolling stock. A technique of inertial dynamic tests of the deformed state of a tunnel overpass from prefabricated metal corrugated structures during the passage of railroad rolling stock is given, by measuring accelerations at the top and on the sides of overpass structures. An algorithm is proposed for processing the acceleration signal for assessing the strained state of metal corrugated structures of a tunnel overpass under the action of dynamic load from railroad transport. Experimental dynamic measurements of accelerations arising at the top and on the sides of a tunnel overpass during the passage of passenger and freight railroad rolling stock were carried out. The maximum value of accelerations arising at the top of a tunnel overpass during the passage of a freight train was 7.99 m/s2, and when passing a passenger train – 6.21 m/s2; the maximum accelerations that occur on the sides were 2.63 m/s2 and 1.77 m/s2. It is established that the maximum deformations of metal corrugated structures of the top of a tunnel overpass, when passing freight and passenger trains are, respectively, 1.63 mm and 1.11 mm. The maximum strains of metal corrugated structures on the sides of an overpass are 1.07 mm and 0.48 mm. The value of relative deformations in the vertical and horizontal dimensions of the structures of a tunnel overpass under the action of dynamic loads from the railroad rolling stock has been found. The relative vertical strains of an overpass amounted to 0.020 %; horizontal – 0.012 %. The practical significance of this work is that with the help of the devised procedure for measuring accelerations, it is possible to assess the strained state of metal corrugated structures under the influence of dynamic loads from the railroad rolling stock