The article presents the results of experimental studies of the complex stress-strain state in reinforced concrete structures with a round cross-section, made of B25 concrete, which includes graphs of deflection and rotation angles, as well as the dependence of concrete deformations obtained from the indications of strain gauges. The main deformations of elongation (and shortening) of concrete were determined by an experimental method using the proposed scheme for installing strain gauges. Rebar for experimental structures was selected in such a way that it achieved yield stress in the stage before destruction.The obtained experimental data allow us to evaluate the calculation method for circular cross section structures in the considered stress state, in particular checking such calculation parameters as the values of the general load of crack appearing and the level of thisload relative to the distruction load; distance between cracks at different levels of crack formation, width of cracks opening at the level of the main reinforcement axis and at the distance of two diameters from the reinforcement axis, coordinates of spatial cracks formation, schemes of crack formation, crack development and crack opening. The experiment found that the width crack opening at the level of the main reinforcement axis is two to three times less than at a distance of two diameters from the main longitudal (or transverse) reinforcement axis. The parameters and crack patterns established during the experiments allow us to clarify the accepted working hypotheses for constructing a calculation model of the resistance in reinforced concrete structures of circular cross-section under torsion with bending.

Structures experiencing torsion strains are widespread in construction, therefore, the development and improvement of methods for calculating such structures is one of the urgent problems of building mechanics and elasticity theory. Exact solutions can be obtained only for rods with an elliptical and rectangular cross-section; in other cases, it is necessary to resort to the use of approximate analytical or numerical methods, many of which are quite laborious. In this regard, the purpose of this article is the demontration of new possibilities of applying the interpolation methods to solving problems of free torsion of prismatic rods. The article compares the values of reduced geometric stiffness of straight-angle cross sections for free torsion of a rod, obtained using exact and approximate solutions. The exact solution is presented depending on the ratio of the sides of the rectangle, and the approximate solutions - depending on the geometric arguments - the shape factor and the ratio of the conformal radii (inner to outer). In the first case, for rectangular sections in the range 1 < a/b< 8, the error of the solutions obtained is 2%, and in the second case, 3.2%.

N the XXI ^th centurypracticallyinallcountries, erectionsin the form of analytically non-given surfaces areappeared. Architecture of arbitrary shapeswasspringingup. Architectsusedtheirentire arsenal of analytical surfaces suitable for realization of their creative ideas. The investigations carried out in RUDN showed that only 43 analytical surfaces from 600 known surfaces found the application in the World at present time. But many noted and young architects and designers began to use surfaces that are impossible to give by analytical formulas. Their intentions were realized into many civil, public, and industrial erections and they came to be as the architectural sights of the towns and countries equally with the erections built before in the form of canonical surfaces. In a paper, the examples of the most interesting buildings are presented; the classification of shells and shell spatial structures of free forms is given according to their analysis schemes, material, and structural solutions. The aim of presented research is to elucidate an extent of involving of architects, geometricians, and designers into working up and building of shells and rod structures in the form of analytically non-given surfaces.

It is known that in the case of dynamic influences, the important dynamic characteristics of the structures of a structure are the frequencies and forms of natural vibrations, with which its response to dynamic effects is associated. These structures include structures lying on the ground, which can be considered when calculating them as beams on an elastic foundation. Using the method of initial parameters for a beam with free edges located on an elastic base, the problem of determining the influence of the attached mass m1 on the circular frequency of natural transverse vibrations (without taking into account the resistance forces) is solved, the first three frequencies and forms of natural transverse vibrations of the beam are determined. The problem of determining the efforts in the beam, taking into account its own weight and dynamic load (perturbing force) F (t), with the frequency of forced vibrations corresponding to the resonance and interresonance zones applied at an arbitrary point d, was solved. The conditions are formulated that must be taken into account when analyzing the dynamic behavior of a structure under the action of variable loads in various design situations.

We consider the relationship between the maximum deflections from a static uniformly distributed load W0 and the basic frequency of proper transverse vibrations of an annular isotropic plate under inhomogeneous support conditions along the outer and inner contour, depending on the ratio of the radius of the inner ring to the outer radius of the plate. Based on the results of the study, graphs of the dependence of the maximum deflection and the frequency of natural vibrations of the plate on the R/R ratio are constructed. It is shown that for annular plates at r/R =0.75, the K coefficient coincides with the same coefficient for single-span beams with non-uniform boundary conditions to an accuracy of 4%.

The approach to the design of steel frame structures is considered, taking into account the potential risk of occurrence of emergencies associated with their mechanical local damage, and possible material losses. It is proposed to classify these systems according to the safety level of the solution. In accordance with the introduced classification, methods for finding solutions are proposed based on the use of evolutionary modeling with subsequent risk assessment from the onset of an emergency. These methods include a combination of two-level stochastic optimization procedures. At the first level, a search is performed on discrete sets of design parameters of a design variant with a minimum cost. As constraints in the absence of emergencies, regulatory requirements of limit states are accepted, and the strength ratio is regulated. In a possible emergency for the construction is considered a limitation on survivability. At the second level, a heuristic search is performed for the design variant for which the risks of receiving material damage from an accident are minimal while ensuring a minimum of capital investments on the considered stages at building life cycle. Examples of the steel frame design with different levels of safety are given, which demonstrate the efficiency of the proposed approach.

The article discusses the multimodal nonlinear static method (MNSM) in assessing the seismic resistance of high-rise structures. The object of the study is a wind power plant 80 meters high. The article proposes a method for taking into account the higher forms of vibrations, as well as a modified algorithm for finding a characteristic point when assessing seismic resistance by a nonlinear static method. To verify the results obtained, the calculation for the seismic effect of the level "Maximum Design Earthquake" ("MCE") was performed using the direct dynamic method, taking into account the possibility of development of inelastic deformations and local brittle fractures in the load-bearing structural elements. A comparative analysis of the results was carried out, according to the results of which the error in the calculations does not exceed 12%.

The method of experimental analysis of concrete and reinforced concrete elements is given in order to determine the parameters of concrete deformation under static loading to a given level, followed by a single dynamic high-speed loading by a shock load. Tests of samples are carried out by means of mode static-dynamic loading, which is carried out using a specially designed device that allows you to fix a given level of static loading of the test specimen and load it from this level by a shock load with the specified dynamic parameters. The developed method static-dynamic tests, the priority of which is protected by a patent of the Russian Federation, allows to experimentally determine the parameters for diagrams of deformation of concrete such as dynamic modulus of deformation, dynamic strength of concrete, the ultimate strain of concrete at different conditions considering static and dynamic loading, and the change of the coefficient of dynamic strength of concrete under different levels of initial static load. The analysis of test results the first series of concrete prisms and deformation the strength and time parameters for tested samples and also obtained using ultrasonic PULSAR 2.1 of stress changes and volume deformation of concrete under these modes of loading.

The research is based on identified archival and printed sources, as well as on-site research by the author, which allows us to reconstruct the architecture of lost and preserved fragments of noble and merchant estates in the territory of the Russian border region during the "Golden age" of the Russian estate. The scientific novelty of the research is associated with the author's expeditions to identify signs of existence and field survey of a number of preserved manor complexes that did not previously attract the attention of researchers. Of particular importance is the identification of archival and printed sources that allow us to reconstruct more reasonably the figurative and material structure of the lost elements of noble and merchant estates. The special significance of the completed complex research work is due to the possibility to fill in the gaps in the study of important pages of the history of national and regional Russian culture, which were reflected in the formation of regional features of construction techniques and imagery of architectural ensembles of estates in the Kursk region.

The use of injection mixtures based on finely dispersed mineral binders (microcements) intended for injection formation of hardened massifs (soil concrete) in permeable soils (sands of all kinds) makes them economically feasible in solving a wide range of different geotechnical problems. For the correct assignment of the parameters for the use of finely dispersed binders for the injection of soils, appropriate criteria for assessing their properties have been developed. However, the question of assigning the consumption of raw materials to obtain soil concrete structures and hardened massifs with the required properties remains poorly studied. Nowadays, the regulatory framework for finely dispersed binders (micro binders) used in injection is practically not presented in the Russian Federation. There is no scientific basis for the formation of soil concrete formed by injection, including there are no adequate dependencies like the Bolomey-Skramtaev formula for concrete, which reflects the resulting strength from the consumption and quality of the components. The series of experiments were conducted, showing the inapplicability of the basic laws for standard concrete when creating soil concrete obtained by injection methods. Various types of finely dispersed binders used in geotechnical construction are considered. As control parameters, the particle size and mineral composition of finely dispersed binders were compared. There were assessed penetration at different modes of preparation and injection of the injection mixture into the soil, and the characteristics of the resulting concrete. Two technologies for creating soil concrete - by mechanical mixing and by the method of injection impregnation of control samples of sandy soil were compared for compliance with the principles of selecting the composition of existing regulatory documents for heavy and light concrete. Significant differences between the properties of soil concrete obtained by the methods of injection impregnation and mixing are confirmed. Studies have confirmed the possibility of injection impregnation with binders of a certain composition in order to strengthen sandy soils in accordance with the assigned technological parameters. The coefficients of the efficiency of the use of micro binders during injection are shown, data on the properties of the formed soil concrete at different technological parameters are reflected.

The problem of industrial waste disposal is becoming more acute every year. The environmental situation in our country and around the world is steadily deteriorating. Natural resources used by humans are also declining, which also necessitates their replacement with alternative sources. In this regard, the problem of obtaining effective composite construction materials and products using industrial wastes is becoming increasingly urgent. A promising direction of solving this problem is application of contact-condensing hardening technology. The article presents the results of the study of strength properties of composites made using cement dust, glass and slag. The results of the study of physical and mechanical properties and resistance under the conditions of aggressive media are given. Various ways of combining components of these composites have been investigated. As a result, industrial waste materials having improved strength characteristics, resistant to various aggressive media are obtained.

Since the second half of the 20th century, many attempts have been made all over the world to create polymer composites with enhanced performance characteristics by modifying them with additives such as rubber, mineral filler, and also organic and inorganic particles [2-3]. To achieve enhanced performance properties of composites, manufacturers introduce combinations of various modifier additives into epoxy matrices, the use of which allows solving most of the problems associated with the operation and durability of polymeric materials. Currently, the most successful fillers of epoxy systems are the most successful carbon nanotubes (CNTs), which are rightly considered ideal additives for polymers because of their high strength and tubular structure [18-20]. In this study, we studied the effect of halloysite nanotubes (HNTs) on the mechanical properties of cured epoxy-based samples. Mechanical tests were carried out according to the methodology of national standard of the Russian Federation GOST R 56800-2015 “Polymer composites. Determination of mechanical tensile properties of unreinforced and reinforced materials” (ASTM D638-10 “Standard test method for tensile properties of plastics”). The following results were obtained: uniaxial tensile strength was improved by + 18.58%, elastic modulus - by + 6.90%, elongation decreased by -15.57% in samples containing 10 wt% halloysite. In this study, halloysite nanotubes have been shown to be effective as an epoxy filler compared to CNTs - halloysite particles are more preferred because of their low cost.

Over the past 150 years, artificial marble has been used, which can have a variety of colors and textures, and also has the ability to easily take the required shape in the manufacture of parts of any complexity. There are many ways to obtain artificial marble and formulations of mixtures, most of which include cement as a binder and quartz sand as an aggregate. This paper shows that ground glass waste can be a substitute for quartz sand or a part of it in the preparation of mixtures for producing artificial marble, which leads to an increase in the strength of the material in compression and a decrease in its water absorption. Black iron oxide pigment, light ocher, redoxide have been approved as coloring additives in the production of artificial marble. It is proposed to unevenly distribute these additives in mixtures with the inclusion of ground glass waste, which makes it possible to achieve an approximate similarity in the appearance of the resulting material with natural marble.