Existing methods for detecting of railway bridge scour do not exclude the occurrence of unforeseen emergencies. This is due to the impossibility of performing work during the flood period, as well as the rather rare frequency of depth measurements on small and medium-sized bridges. Therefore, the aim of the study is to improve the operational reliability of railway bridges by improving the method for detecting bridge scour by the natural vibration frequencies.
In the course of the study, in order to establish the actual dynamic nature of the operation of the railway bridge piers, full-scale measurements of the natural vibration frequencies were performed. The vibration measurement carried out for 30 supports of various designs at the actual depth of foundations. The measurements used the multifunctional measuring system “Tensor MS”. Computational studies completed to predict changes in the fixed natural vibration frequencies during the development of bridge scour. The developed mathematical models of piers take into account the compatibility of their work with superstructures and interaction with base soils. In this research, nature of the work of the carriages with free vibrations of the structure is estimated. Also, the required degree of detail in the modeling of structures is established to obtain data corresponding to the actually recorded ones. The assessment of the conformity of the model to the actual dynamic nature of the operation of the supports is made by the value of the design coefficient. After verification of the calculation models for all objects of study, the calculation and experimental dependences of the natural vibration frequencies of the piers on the depth of bridge scour are revealed.
The introduction of an improved method for monitoring soil erosion of railway bridge scours will improve the operational reliability of railway bridges, as well as reduce the cost of carrying out work to control the depth of bridge scours.

The article outlines the problem of directive assignment of the bridges service life in the current regulatory documents, in the absence of mechanisms for calculating and justifying these terms for a particular structure taking into account the conditions of its operation. The service life is one of the defining characteristics responsible for the main parameters of the bridge structure. The existing promising approaches that can be used to predict the durability of bridges are listed, as well as the main defects that are often encountered when examining reinforced concrete road bridges. This study proposes a method for determining the service life of a reinforced concrete slab of a carriageway of a beam span, based on the description of the mechanisms of degradation of the protective layer and the kinetics of corrosion processes. The period of degradation of the protective layer is described by two processes running in parallel: the carbonization of concrete, as well as the penetration and accumulation of chlorides to a critical value. The description of these processes is based on the fundamental laws of the Fick's laws of diffusion. The model of changes in such climatic parameters as ambient temperature and humidity is proposed to be represented as a sinusoidal function. A piecewise linear function of the change in the surface concentration of chlorides over time is proposed, simulating a sharp increase in the concentration in the winter period from the treatment of the carriageway of road bridges with anti-icing materials. A stochastic approach is presented that makes it possible to take into account the random nature of the initial parameters, which is based on the Monte Carlo method. The calculation was carried out in accordance with the stochastic model of the reinforced concrete beam superstructure of the bridge. Based on the calculation results, distribution histograms of the main service life periods were obtained, and integral distribution functions were constructed.

The design and construction of high-speed railways is accompanied by the need to consider certain loads and impacts that are not considered, as a rule, when designing conventional railways. It is one of such special loads, the consideration of which is mandatory when calculating infrastructure facilities of high-speed railways is the load from the aerodynamic impact of moving high-speed rolling stock One of the structures most susceptible to aerodynamic effects are pedestrian overpasses, which is due to their relatively small mass and proximity to a moving train. Performed analysis of domestic and foreign standards and the methods of accounting for the aerodynamic impact from a moving high-speed train showed that they lack a few calculated cases characteristic of pedestrian crossings, road overpasses, concourses, etc., namely, the impact on vertical surfaces located above the dimension perpendicular to the axis of movement of the train.
This paper examines the study of the aerodynamic effect of a high-speed train on a pedestrian overpass. Analysis of the results of the performed series of calculations made it possible to establish the nature of the pressure distribution on the surface of the structure under consideration, including on the frontal surface. The nature and intensity of the force impact on the structure, namely the longitudinal one, was also determined and lifting aerodynamic forces, depending on the position of the moving train and design parameters such as the height above the level of the rail head and the distance from the section under consideration to the axis of movement of the train.
In conclusion, proposals are made to improve the existing methods of accounting for aerodynamic effects.

The study of the dynamic operation of span structures of bridges under the influence of a high-speed temporary railway load is necessary for the correct modeling of oscillatory processes that occur in the structures of a bridge structure. Creation of complete computational models of dynamic interaction of the bridge – track – train system makes it possible to determine the permissible speeds of high-speed trains both on bridge structures in operation and for bridges under design. The article presents the results of experimental studies obtained during field dynamic tests of steel-reinforced concrete superstructures of a bridge structure located on the St. Petersburg – Moscow railway line during the passage of the high-speed train Sapsan. During the field experiment, measurements were made of accelerations and displacements that occur in the structures of superstructures under the influence of high-speed rolling stock. With further processing of the results of field measurements, two calculation models are considered to evaluate the dynamic operation of the structures of spans and rolling stock. As the first, a simplified model of a single span is taken, considering the impact of the rolling stock in the form of a model of successively located forces corresponding to the scheme of the rolling stock. The design scheme does not consider the stiffness and damping of the track superstructure and the dynamic parameters of the rolling stock. Considering the discrepancy between the experimental and calculated data during further research, a more complex model is considered, considering all span structures in the bridge, according to the construction scheme, stiffness and damping parameters of the track structure and rolling stock. The dynamic calculation of the interaction of the elements of the bridge – track – train system is carried out in a non-linear non-stationary formulation.
Based on the data obtained, the indicated calculation models are verified for compliance with the results obtained during a full-scale experiment, the areas of their rational application, as well as advantages and disadvantages, are determined.

The planned high-speed railway line Moscow – Saint-Petersburg makes high demands on the reliability and durability of artificial structures in its composition. The service life of the main load-bearing structures of bridges is prescribed by design standards at the level of 100 years, while there is no possibility of its justification and calculation confirmation. Operating experience allows us to conclude that single structures on existing railway lines reach such a period without reconstruction or major repairs. This article discusses corrosion-fatigue durability as one of the aspects of the method for predicting the service life of a bridge, taking into account the dynamic load. This type of degradation of reinforced concrete is caused by the combined action of pitting corrosion of reinforcement and cyclic loading, which leads to the initiation and growth of a fatigue crack in the reinforcing bar. A method for calculating the time of crack growth from its inception to a critical value is given. The methodology includes modeling and dynamic calculation of a reinforced concrete frame span of a bridge, processing the bending moment spectrum and extracting the average stress value and the number of its repetitions, modeling crack growth using the principles of fracture mechanics. Trains A1-A10 were analyzed along SP 453 in the speed range from 120 to 400 km/h. The values of the fatigue crack growth time for the selected trains and speeds, which cause the largest range of stresses in the reinforcement, are obtained.

The article presents a methodology for non-destructive testing of the appearance and development of fatigue cracks in the elements of steel bridges at all stages of their development using infrared thermography. Methods of thermal non-destructive testing based on energy balance (dissipative heating method and thermo elastic stress analysis method) are described, and the temperature gap method is introduced. The place of each method at each stage of the development of fatigue cracks is shown. The dissipative heating method is applicable at the stage of crack initiation and makes it possible to establish the cyclic durability according to the criterion of macro crack initiation based on the analysis of energy dissipation during inelastic deformation. The method of analysis of thermo elastic stresses makes it possible to identify areas in which there are stress concentrations caused by internal imperfections and fatigue micro cracks, to evaluate the stress intensity factor, to evaluate the change in the stress state after repair work on the structure, and to establish the exact position of the crack tip. The temperature gap method is based on the thermal insulation effect of the crack. Despite the fact that this method as a whole is of an auxiliary and approximate nature, however, it has the advantage that, unlike methods based on energy balance, it does not require mechanical action, which opens the way to its practical application. For this, as a rule, natural heating of the structure is sufficient, however, additional stimulation by an external heat source can be used. The results of applying the presented methods of thermal non-destructive testing for crack detection and structural integrity assessment both in laboratory conditions and on bridges in operation are presented.

The development and reconstruction of the transport infrastructure of cities and their agglomerations cannot be imagined without pedestrian overpasses. They allow you to increase the throughput of roads with a relatively small investment, while ensuring complete safety of pedestrian traffic. The span structures of pedestrian bridges are relatively light in comparison with road spans, which makes them sensitive to dynamic influences of various nature, as well as to simplifications and neglects generally accepted in engineering calculations.
As confirmation of this assumption, the paper presents the results of testing three pedestrian bridges built in 2009–2012 in the Far East region. The test results substantiate the proposed concept of regulation of the dynamic characteristics of span structures. The essence of the concept is the use of polymer bearing parts with a given shear stiffness and damping properties, which makes it possible to effectively control the dynamic characteristics of the span. It is proposed to use polyurethane of various grades as the base material.
Due to the lack of reference data on the physical and mechanical characteristics of polyurethane of various stiffness (hardness), experimental laboratory studies were carried out, as reflected in this article. As part of the experiment, three series of bearing parts were made from rubber and polyurethane of various grades. As part of the experiment, three series of bearing parts were made from rubber and polyurethane of various grades. As a result of the study, the shear modulus values of interest to us for the tested materials were obtained. In addition, during dynamic tests, signs of high dissipation of polyurethane were revealed compared to rubber used in bearing parts, which confirms its effectiveness as a damping element in a pedestrian superstructure.
The materials presented in the article substantiate the practical significance of the study, and the results obtained will be applied in modeling bearing parts for real objects.

Currently, the issue of the development of the northern regions of Russia due to the expansion of the network of railways and highways is acute. However, the regulatory framework for the design, construction and operation of bridges does not fully take into account the impact of natural and climatic changes, as well as the degradation of frozen soils on artificial structures throughout their life cycle. In order to improve building codes, it is necessary to conduct research about the problems arising in the process of operation in the conditions of the Far North. The creation of methods to solve these problems will improve the operational reliability of existing bridges. Therefore, it is necessary to develop a system for monitoring and maintaining artificial structures, including improving methods for monitoring the technical condition of bridges. Within the framework of this study, such methods as vibration diagnostics, electrotomography, electro profiling and georadar sounding were used to examine bridges built in the cryolithozone. The research was carried out at a landfill of 21 road bridges located on the Surgut – Salekhard and Labytnangi – Harp highways. The comparison of the considered methods testifies to the prospects of the method of vibration diagnostics. The natural oscillation frequency of the structure is taken as the main controlled parameter. A change in the frequency of vibration of the supports will indicate a change in the stiffness of the base of the bridge supports and the thawing of frozen soils. To better substantiate the results of the study, it is planned to organize monitoring of soil temperature, as well as perform geological surveys with the specification of the characteristics of the foundation soils.

The most important task of the Russian road industry is the qualitative improvement of the condition of highways and artificial structures on them. According to official data, about 30 % of bridge structures located on highways of regional and inter-municipal significance are in unsatisfactory, pre-emergency and emergency condition.
The aim of the author was to develop a new structural and technological solution for strengthening the span structure of bridge structures to significantly increase their carrying capacity, carrying capacity while maintaining traffic on and under the structure for the period of reconstruction. The article describes the author's research on the problem under consideration, including an analysis of the applied reinforcement methods, including a generalization of existing technical solutions, describes full-scale tests of the proposed method on a specially manufactured test bench. The advantages and specific examples of successful application of the method in the repair and reconstruction of facilities are given.
The method is based on a new approach to reshaping reinforcement elements – not in each separate beam, but by combining two or three adjacent beams into a new monolithic box. Moreover, such a design can be used to strengthen a separate split span, or it can also be used for reconstruction into an uncut span structure when replacing a set of supporting parts.
It turns out a completely new superstructure design, which is a box-shaped monolithic continuous solid beam, where the former beams of the split beam system serve at the first stage only as a fixed formwork, and at the subsequent stage, having joined in joint work as a "frame element" in the center of which there is a monolithic stressed structure.