This paper deals with the peculiarities of calculating the seismic resistance of reinforced concrete railway bridges based on real earthquake records. Using finite element and finite difference methods, the problem is discretised by taking into account the interaction between the foundations of the bridge piers and the ground according to the Winkler model and the prestressing of the span structure. The prestressing of the span is provided by the stressed elements of the working reinforcement. The coefficients of the interaction stiffness matrix are calculated from the areas of the contact surfaces of the suspension piles with the soil.

The example of calculation of a three-span reinforced concrete railway bridge for real seismic effects of earth-quakes shows the influence of the prestressed state of the span during an earthquake. The 53.2 m long railway bridge is located in the area of 7points in seismic intensity between Shavat – Gurlen stations, which is located on the railway section Shavat – Gurlen – Jumurtau – Kipchak – Koibakli. Numerical solution of the problem of earth- quake resistance of the bridge shows the change of its stress – strain state in time. The results of calculation of the railway reinforced concrete bridge are obtained on the basis of real records of earthquake “Boshroyeh” (Iran) with intensity of 7 MSK-64. According to the calculation results, we conclude that the normal stresses in the spans, without taking into account prestressed reinforcement, become tensile from the bottom side. Since the tensile strength of concrete is poor, it causes gradual cracking of the span, resulting in a shorter span life. According to the obtained results, without prestressing the reinforcement of the railway bridge, the calculated values were higher than the tensile stress values allowed by the normative documents by 0.45 MPa. Taking into account the prestressing of the reinforcement, the stress values corresponding to those accepted in the normative document were obtained.

Issues related to the operation of artificial structures in the northern construction and climatic zone, which covers 40 percent of the territory of the Russian Federation and 80 percent of the territory of the Russian Far East are important in all aspects. At the same time, we are talking not only about existing artificial structures of the transport infrastructure, but also about objects under construction, as well as about objects planned for construction. For example, in the territory under the jurisdiction of the Far Eastern Railway, there is 1 object per 1 km of track belonging to small artificial structures, these objects are located in the cryolithic zone, which imposes additional requirements for monitoring the technical condition and carrying out additional measures aimed at preventing the transition of the object's structures to an emergency state. The currently existing methods of monitoring the technical condition make it possible to control and predict with a high degree of reliability possible conditions, causes and consequences of incidents, however, taking into account the growth of the possibility of digital modeling, visualization and forecasting, it is advisable to use all available possibilities for the formation of digital models of artificial structures objects, for the most effective preservation of their working condition.

The article reviews an example of numerical modeling and digital simulation of base and foundation of artificial structures, given a solution of the numerical task of thermal fields distribution, also solved a numerical task with a forecasting of changes in the time perspective. The purpose of this research was assessment of possible negative events at various stages of the artificial structure’s life cycle and establishing a digital model for the forecasting safe operations.

As a result, a digital model of foundations was obtained, which can be used to solve various tasks.

In this article, the object of research is the structures of engineering protection of bridge crossings from the hydrodynamic effects of the marine aquatic environment. The problems of design and evaluation of wave effects are considered in order to choose a method of engineering protection.

Mathematical modeling of wave conditions and lithodynamic processes in the coastal zone was performed using the example of a specific section of the Tuapse – Adler North Caucasian Railway. To protect against erosion by sea waves of five railway bridges located on this site, as well as the earthwork of the railway, three variants of engineering protection structures are considered: an artificial free beach (protective wave-extinguishing strip) with periodic operational replenishment, an artificial beach with beach-retaining structures (buns) and a wave- extinguishing berm made of stone.

The research was carried out by the method of mathematical modeling out according to the programs of Professor K. N. Makarov, implementing models of wave propagation and transformation, as well as lithodynamic processes of the coastal zone of the seas, which are the basis of the normative methods of SP 38.13330.2018 and SP 277.125800.2016.

Modeling of wave generation in deep water, their transformation and refraction in the coastal zone of the sea, as well as calculations of long-range sediment transport were performed using the developed digital terrain models.

Based on the results of mathematical modeling, the parameters of wind waves affecting structures in the offshore coastal zone of the site under consideration and the parameters of long-shore sediment transport were obtained. The volume of deposits to create a protective wave-damping band was determined, and the beach-holding capacity of the bun was evaluated. The parameters of the wave damping berm are determined.

The anchorage zone of a prestressed reinforcement element is a critical area of the reinforced concrete structure. The manufacturer of the prestressing system is only responsible for the local area – the area of concrete for which the confinement(local) reinforcement is designed. The analysis of national and international literature carried out by the authors has shown that when using complex forms of anchoring devices, confinement (local) reinforcement is difficult to select by analytical methods, and changes in its design must be confirmed by full-scale tests.

The article presents the experience of local reinforcement design for the OS-55 bearing plate by STSd, which has a complex shape and is used in nuclear power plant (NPP) containment. Requirements for testing of anchor zones are given. The description of calculation schemes with indication of applied models and properties of materials, assumptions in calculation is made. Methodology of testing according to European standards with indication of stages of loading, controlled parameters and scheme of installation of measuring devices is described. The results of calculations, tests and their comparison are given. The difference between the calculated and experimental values of displacements of the support surface of the bearing plate was not more than 2.9 % at loading levels of 80-105 % of the characteristic ultimate resisting force of the tendon. According to the methods of two national codes the calculated values of crack opening widths at the loading level of 80 % of the characteristic ultimate resisting force were determined. The theoretical and actual values were compared, the difference was not more than 3.5 %.

On the basis of comparison of the calculation results with experimental data, obtained during testing, the conclusion about successful verification of the accepted methodology of anchor zone design was made.

The paper presents some results of measurements of relative strains and stresses in the middle section of reinforced concrete spans of the railway overpass from the impact of static loads, obtained with the use of hardware-software complex TENZO, which implements the interpretation and processing of digital records of primary transducers. The dependences of the stress-strain state of the girder spans of the railway overpass under static application of the test load consisting of the cohesion of three TEM-18 diesel locomotives and two loaded gondola cars (up to 25 tones per axle) were obtained. The purpose of this study was to ensure reliable and safe operation of artificial structures, and bring them into compliance with the requirements of the Rules of Technical Operation of Railways of the Republic of Kazakhstan. Periodic measurements of deformations of the span structure during 3–5 years allowed to forecast changes in its condition over time and determine the residual life in terms of load-bearing capacity and load carrying capacity. The differences in the numerical values of stresses in the elements of the railway overpass (right and left block) are a consequence of uneven wear of structures due to climatic factors. The results of the study are recommended to be used for inspections and tests of typical girder bridge spans, as well as in case of monitoring their technical condition under increasing operational loads. The safety of transport infrastructure facilities depends on the application of progressive technologies and scientific methods of monitoring to solve technical issues at all stages of operation. The use of digital hardware and software complexes in testing of bridge girders will significantly reduce the cost of current maintenance of artificial structures.

The technical condition of bridge structures in the form of farms used for railway traffic is the subject of wide scientific discussions at present. Ensuring this technical condition is a rather significant scientific problem, the solution of which is now becoming increasingly practical. Obviously, one of the most effective tools for managing this technical condition of such structures is the monitoring of engineering structures. A brief technical and operational analysis of railway farms was carried out in the article, highlighting the main problems of their maintenance. The existing monitoring systems (subsystems) were reviewed with a brief description of their operating principles. Proposals for improving existing solutions and approaches to monitoring are described. The relevance of considering this issue is especially important when justifying the optimal number of controlled parameters. This question constantly arises when design documentation undergoes state examination, as well as when communicating with the customer when justifying costs. It is especially important at the stage of developing a monitoring program to take into account the need to analyze the structure from the point of view of its representation by the monitoring object. Obviously, this requires a transition from the subjective determination of control points based on an ideal structure model to strict mathematical dependencies. The condition of the structure in this case, characterized by the number and types of defects, as well as an assessment of permanent and temporary impacts. As an example, data are given on the survey of two bridge structures for a railway with spans in the form of trusses.

The paper considers an approach to determining the stress intensity factor (SIF) in the fatigue crack tip based on the principles of thermodynamics. The proposed approach is based on the Vestergaard model – the change in the SIF ΔKI value per observation cycle (e.g., during the time a train passes over a bridge) is determined from the data on the stress state around the crack tip. Such data are obtained by infrared thermography using the Kelvin relationship between the change in the sum of principal stresses and the change in surface temperature near the crack tip. Knowledge of the crack length is not required to calculate the SIF.

The paper presents the results of experimental studies of fatigue crack development on a specimen simulating the operation of a section of a beam wall of a metallic span structure supported by a stiffener with a notch at the top of the weld. Such sections are characterized by the development of fatigue cracks of T-9 and T-10 types.

The paper discusses the conditions of application of infrared thermography method for determining the stress field around the crack tip, defined the boundaries of the stress selection area for calculating the SIF, as well as the requirements for improving the signal-to-noise ratio when using thermography.

The results of the study are presented in the form of comparison of SIF values for experimental specimen at different length of fatigue crack, calculated by the known method of linear fracture mechanics and the developed method based on thermodynamic approach, their good coincidence is shown.

Cable-stayed bridges are one of the most complex structures in design, construction and maintenance. The cable is flexible load–bearing steel element with a low level of structural damping. Cable vibrations with significant amplitude can cause fatigue damage to the cables, which reduces the safety and reliability of the structure. Hydraulic dampers are an effective way of damping cable vibrations.

The article presents the experience of development, installation and testing of the first national cable-stayed system STS with parallel seven-wire strands on the bridge over the Oka River on the M-12 highway in Murom.

The purpose of the research is the experimental verification of the methodology of hydraulic dampers characteristics determination to achieve the required logarithmic decrement of cable vibrations after their installation. The author does not consider the methodology of theoretical calculation of the characteristics of dampers in this research.

A test program has been developed to achieve this goal. The selected method of vibration diagnostics for dynamic tests of cables is applicable to verify the logarithmic decrements of cables with dampers. The dependence of the values of the logarithmic decrement of vibration on the amplitude of vibration is revealed. The operability of the damper installations has been proved for all tested cables.

The values of the logarithmic decrement of the vibrations of the cables before the installation of the dampers are in the range from 0.5 to 3.0 %. After installation of the dampers, the values of the logarithmic decrement of vibrations ranged from 5.45 to 11.85 %, which is more than the minimum required value of 5 %.

The actual values of the logarithmic decrement of parallel strands cables, rare for the construction of cable-stayed bridges and valuable from a scientific point of view, were obtained on the same cables before and after the installation of dampers under the same constant loads on the superstructure.

In order to improve the transport infrastructure of the Republic of Uzbekistan, they began to use the monolithic structure of bridges and overpasses. The article presents the calculation of a monolithic overpass with a length of 120 meters, located in the area of 8-point seismicity according to MSK-64 in the city of Jizzakh over the high-speed railway lines Tashkent-Samarkand (Republic of Uzbekistan). A numerical solution to the problem of seismic resistance of an overpass determines the change in its stress-strain state over time. The results of calculating a monolithic bridge under dynamic load based on records of real accelerograms of the Gazli (Uzbekistan) earthquake, with an intensity of more than 9 points on the MSK-64 scale, are presented. The results of calculations of changes in normal stress in the upper and lower parts of the span along the length of the bridge are analyzed. The calculations show that the bridge has a safety factor for a magnitude 9 earthquake. To ensure guaranteed seismic safety of bridge structures, it is necessary to carry out design calculations based on sets of records of earthquakes that have occurred that are close in dominant frequencies to the characteristics of the construction site.

This article discusses the use of vibration mats on the superstructures of railway bridges with ballast riding and mating sections of the roadbed. Numerical experiments were carried out using finite element modeling in the Midas FEA software package. The article presents the results of calculating the stiffness of various types of sub-rail base, different design of the rail grating, a ballast layer with different modulus of elasticity and sub-ballast vibration mats laid under the ballast. Spatial diagrams of vertical pressure along the surface of the ballast trough slab were constructed, taking into account the rigidity of the under-rail base, indicating graphs of pressure distribution through the elements of the superstructure of the track in the thickness of the ballast layer. It has been established that the rigidity of the under-rail base in the presence of vibrating mats decreases, which leads to a decrease in the ordinate value of the spatial diagram of vertical pressure along the ballast trough slab, by including a longer section of the rail and sleeper grid in the work. A calculation of the load-carrying capacity of the ballast trough slab in the presence of vibrating mats was carried out, as a result of which an increase in the minimum classes for the load-carrying capacity of the ballast trough slab up to 30% was noted. The dynamic calculation indicates the presence of subsidence of no more than 20 mm with a tonnage production of up to 330 million tons gross on an equally elastic path with mats on the superstructure and approaches, which ensures equal elasticity of the path, the absence of “bridge pits” and equal resource life of the path in the area where the embankment meets the bridge structure.