A step-by-step finite element method calculation algorithm of concrete filled steel tubes is provided with an example. A comparison of the finite element calculation results with experimental data, calculations according to Russian (SP266.13 25800.2016) and European standards (Eurocode 4) and the “inverse” numerical-analytical method, which takes into account the actual rigidity of sections, is given as well. The study shows an accuracy of the proposed finite element model using Drucker-Prager model for concrete and the “inverse” numerical-analytical method in comparison with standard calculation methods.

Keywords: finite element method, concrete filled steel tubes, Drucker-Prager model, “inverse” numerical-analytical method, eccentric load

The article presents the results of experimental studies of the operation of mobile wood and metal-wood road pavement and work sites. The results allow to predict with sufficient confidence the stress-strain state of mobile road pavements in real conditions of operation ground as temporary roads, helicopter pads and drilling rig sites.

Keywords: mobile road pavement, demountable plate, temporary roads, static load testing

The process of optimizing the applied sections in steel frames with elements of variable stiffness, formed from rolled I-beams by their diagonal dissolution and subsequent welding, is considered. A table with groups of I-beams according to GOST R 57837-2017 is proposed, which are advisable to be used together to form a monosymmetrical I-beam of variable height. An algorithm for finding the optimal section is proposed, taking into account the discreteness of the assortment. The calculation of a typical building structure code 828KM according to the proposed algorithm is carried out and a comparative analysis of the applied sections with the found optimized sections is presented. The possibility of obtaining a more economical supporting structure, both in terms of metal consumption and in terms of the cost of rolled products, is noted.

Keywords: variable section, variable stiffness, diagonal opening, I-beam, steel frame

A review of publications by Russian and foreign researchers on the issues of modeling the process of assessing the degree of security of individual components of an informatization object (automated system) is presented. The main factors influencing the level of security are analyzed. The types of objects of unauthorized influence are given. The choice of the “information carrier” as the main generalized object and the list of actual threats to it are substantiated, their brief analysis is given. As the output (dependent) variable of the developed regression model, the level of information carrier security is determined. The input (independent) variables are the degree of danger of threats: illegal access to protected information; unauthorized copying of protected information; overcoming physical protection; loss of carriers of information. The developed model has the form of a regression equation and can be used to predict the level of security of information carriers.

Keywords: information security, informatization object, automated system, information carriers, information security threats, security level, regression model, expert information, adequacy criteria

This article presents the main achievements of the foreign engineering school in the field of research and application of composite materials to reinforce wooden structures. Some options for reinforcing glued and solid wooden elements are considered. The results of tests of reinforced wooden structures are analyzed. Errors made during the manufacture of samples and the course of testing are noted. Conclusions are drawn on the basis of the conducted research.

Keywords: wooden structure, prestressing, composite beam, tensile zone, carbon nanotubes, load-bearing capacity, epoxy matrix, carbon fiber, lamella, rebar, wood collapse

The paper is focused on the building heightening technologies employing modular structures, and in particular, three-dimensional units. It lists the global leaders in the field of manufacturing of three-dimensional/modular units and examines the work stages based on the analysis of scientific publications and patent searches. It is noted that the process arrangement upgraded to the current state of the art and the improved energy efficiency performance of a superstructure are mainly achieved through the use of modular units with greater dimensions but with a lighter weight.

Keywords: reconstruction, technology, energy efficiency, superstructure, modular constructions, volume blocks, organizational and technological solutions

This paper is a follow-up on the first part, which also reviews the process arrangement solutions for building reconstruction based on building heightening using modular structures. It highlights the importance of the use of transformer (stacked) modules, which allows improving the work process flexibility at the installation and transportation stages. It is further specified that, if reconstruction is carried out in congested urban environments, three-dimensional/modular units should be prefabricated, as prefabrication helps to significantly reduce a gap between the actual and standardized work timelines, even in case of force majeure.

Keywords: superstructure, organizational and technological solutions, transforming three-dimensional blocks, assembly and transport manufacturability

The article considers the concentration dependence of dust particles PM2.5 and PM10 on a curb stone on a number of influencing parameters. According to the data of field measurements, a quadratic regression equation was compiled, according to which the factors that have the greatest influence on the spread of fine dust near the roadway were determined. The results of mathematical processing of experimental data are presented in the form of a graph of the confidence area of the observed and predicted values constructed using the STATISTICA software product.

Keywords: PM10, PM2.5, fine dust, roadway, linear city, concentration dependence

This paper presents the results of a study of the interaction of the wheel tire with the support surface of the support-running module during the movement of the wheeled vehicle. The creation of a mathematical model of the movement of the wheel on the support base of the support-running module is given. For this, a design scheme for the movement of the wheel along the supporting surface of the support-running module was presented, and the following equations were given: the dynamics of the drive wheel; normal reaction and reaction vector of the interaction of the wheel tire with the support base; partial slip friction coefficient for cohesive soils and slip coefficient. Simulation modeling was carried out using the MATLAB Simulink environment, which allows, on the basis of a given mathematical model, to study the system being developed. When using this system, there is a reduction in the cost of expensive physical prototypes and an increase in the quality of products, as a result of an increase in the accuracy of calculations.

Keywords: wheel tyre, suspension module, wheeled vehicle, MATLAB Simulink, mathematical model, modeling

The forecast of fine dust pollution, the organization of monitoring and quality control of the air environment are relevant for cities with a developed transport infrastructure. The article checks the application of the distribution law for the concentration of fine dust PM2.5 and PM10 for highways of urban, district and local significance, the sample size was 50 values.

Keywords: linear city, distribution law, fine dust, roads, mixed gaussian distribution

Software algorithms for a microprocessor device for active control of the grinding process of bearing rings have been developed.

Keywords: grinding, active control, microcontroller, active control device, active control device software

With the right approach, the heat generated by chillers in an indoor ice rink can be used to melt ice, a dehydration system, or to heat a concrete pad under a layer of ice. In this way, energy can be saved. For the purpose of accumulation and subsequent distribution of thermal energy in the building, a reservoir that accumulates heat can be used. Heat is removed from the chiller condenser by a water cooling circuit, which is connected to the coil of an indirect heating boiler (heat accumulator). The coil heats the water that circulates in the heating circuit. Since the load on the ice can change during the day, heat extraction will occur in different amounts. For efficient transfer of thermal energy from one heat exchanger to another, it is necessary to control the speed of rotation of the pump impeller so that the controlled function is maximum. If the speed is insufficient, then the heat exchange flow will receive less heat. On the contrary, if the drive drives antifreeze too quickly, then the coolant will not have time to heat up. A mathematical model of the system was compiled from a plant condenser and a boiler with heated water, a dependence on the speed of the coolant (antifreeze) and the temperature difference at the inlet and outlet of the accumulator was revealed.

Keywords: heat accumulator, temperature control, shell-and-tube heat exchanger, optimal regulator, freon

The article discusses a new type of reinforced concrete columns with local prestressing of reinforcement. Such elements can be used for high flexibilities and eccentricities of the longitudinal force, for example, in the construction of industrial buildings. The derivation of resolving equations for determining the stress-strain state of the structures under consideration at the stage of prestressing is presented. Equations are obtained for calculating the level of prestresses in reinforcement, at which technological cracks are formed, expressions for determining stresses in concrete and reinforcement, as well as the deflection of the column at the manufacturing stage. The calculation algorithms are implemented numerically in the MATLAB environment. A comparison of the calculation by the author's method with finite element modeling in the LIRA software package in a three-dimensional setting is presented, taking into account the physical nonlinearity of concrete.

Keywords: reinforced concrete, columns, prestressing, stress-strain state, reinforcement, manufacturing stage, technological cracks, deflection

The researches results of the fuel ash waste’s and grain crops straw’s influence on the properties of the producing expanded clay gravel are presented in the paper. These wastes were used as auxiliary additives in the raw combination. The optimal composition of the raw combination has been established in the laboratory, for which physical and mechanical characteristics of the samples, including water absorption, compressive strength, bulk density, were analyzed. Characteristics of the expanded clay gravel samples are compared with the state standards requirements. It was found, that the addition 5% fuel ash and 1.5% crop waste (grain straw) ensures optimal swelling of the combination and high strength characteristics of the finished product.

Keywords: expanded clay, fuel ash, waste of crop production, swelling, construction materials, porosity.

The main elements of the system of external reinforcement of bent reinforced concrete structures are fabrics and lamellas. Fabrics and lamellas are glued to the surface of building structures in a polymer matrix. The matrix provides adhesion of the reinforcing filler with the reinforced structure. The price of reinforcement with carbon lamellas is several times higher than for reinforcement with carbon fabric. The article shows a comparison of proposals on the market of building materials for the reinforcement of reinforced concrete structures with lamellas based on carbon fibers. On the example of a reinforced concrete beam of four types of cross-section, a comparative analysis of the selected reinforcement systems under different temperature conditions was carried out, a conditional utility coefficient was identified, showing the ratio of price to the percentage reinforcement of the structure. The results obtained can be used to select the most cost-effective composite reinforcement system.

Keywords: reinforced concrete beams; strengthening; composite material; carbon lamellas; external reinforcement; operating temperature