The design projection of the inclined section is an important factor in the estimation of strength of reinforced concrete structures by inclined sections. The problem of determination of the crack inclination angle is also essential for the elements strengthened by the external composite rein-forcement. The method of the inclination angle determination in any point along the span of strength-ened bending element is proposed. The design inclination angle of a crack corresponds to the minimum of external load causing its opening, which is obtained from the energy balance equation. The calculations of bending elements strengthened by composite materials have been carried out. The ob-tained dependence of cracks inclination angles on the conventional to composite reinforcement ratio and on the coefficient of the bilinear section hypothesis.

A beam statically determinate truss with an arbitrary number of panels, in one of the nodes of which there is a massive load, is considered. The mass of the rods of the truss is neglected. A formula is derived for the dependence of the vibration frequency of the load on the hinge number in which it is located. The rigidity of the truss in the frequency equation is determined by the Maxwell-Mohr's formula. Forces in rods are determined in symbolic form by cutting out nodes in a program written in the computer mathematics system Maple. By a method of double induction (by the number of the node where the load is located and the number of panels), a series of particular solutions is generalized to an arbitrary case. A recurrence equation that is satisfied by a sequence of coefficients of particular solutions is given by a special operator of the Maple system.

The paper notes the relevance of introducing into practice the calculations of structures on seismic effects of methodologically sound initial data - reaction spectra. In the course of the work, the concepts of pseudo-spectra of responses in displacements, speeds, and accelerations are formulated. The results of determining the relationship between the amplitude Fourier spectra and the spectra of the maximum reactions of systems with damping equal to zero are presented. Relations between the spectra Fourier and response spectra for systems with viscous damping are obtained, similar to the dependences between the Fourier spectra and the response spectrum for non-damped systems (Kawasumi, 1956; Rubin, 1961; Hudson, 1962; Jennings, 1972). In contrast to the work “Damped Fourier Spectrum and Response Spectra” (Idvadia and Trifunak, 1973), the functional Damped Fourier spectrum is not used in our work. The classic Fourier transform is used.

The study of the literature showed the absence of a detailed algorithm for calculating the strength of reinforced concrete elements of a rectangular profile under oblique out-of-center compression using a nonlinear deformation model. This article, which presents such an algorithm, is intended to fill this gap. The peculiarity of the proposed method is that a local coordinate system is introduced for each component of the reinforced concrete section (concrete platform, reinforcing bar) with the beginning of the report located on the neutral axis of the section. This makes it possible to equate the longitudinal deformations to zero, ε ₀ =0, on this axis, and significantly simplify the formulas for determining the curvature and other parameters. The results of calculating the destructive load of Nult using the method are compared with the experimental data presented in the work of M. S. Toryanik. The comparison was made for 7 short samples that differ in cross-section size, reinforcement, concrete class, and load application eccentricity. The similarity of the results is established, the difference is from -6.8 to +6.1 %, which can be considered acceptable, so the proposed method is recommended for implementation in the design standards.

A calculation was made of a centrally compressed concrete specimen reinforced with a tape FRP jackets in the analysis complex Ansys Mechanical software in the Static Structural module. Substantiated models of materials included in the system of "concrete- FRP jackets" and the parameters that determine them. Stress-strain relation for the control and reinforced samples were obtained using different concrete deformation diagrams, which are regulated by the current Russian regulatory documents. It was revealed that when describing the work of confined concrete by a carbon fiber FRP jackets, the correspondence to experimental data is achieved using a diagram of concrete deformation with a yield point. An assessment of the existing regulatory approach to determining the bearing capacity of elements reinforced with FRP jackets. Suggestions were made for the assignment of other criteria for the limiting state that take into account real deformations.

During the development of the buildings design models, very important to take into account the conjugation of prefabricated structures, and to understand whether the continuity of their continuous conjugation will remain under the load. Sometimes errors in modeling can lead to an unreasonable increase in cross sections of structures, their damage, or even an accident during the construction and operation of a building. Below it is drawn attention to the number of tasks in which there are interface problems in the design of buildings and structures from prefabricated structures.

Increase of energy performance of buildings and structures is the subject of the research. Energy consumption both in Russia and abroad is analyzed, and energy performance measures and energy saving technologies at construction and reconstruction of buildings in the developed countries of the world are thoroughly considered herein. History of making thermal imaging devices and diagnostics of engineering structures is presented. Current regulatory framework and procedures for making thermovision inspection are reviewed. Main problems of energy consumption in the Republic of Bashkortostan and the frequent reasons thereof are found. Heat loss rate in Ufa is analyzed, with the results of thermovision inspection of various facilities being conducted, are given. Under the results obtained the reasons for reducing heat efficiency indicators are analyzed, economic efficiency of different insulation methods is defined, and optimum installation of enclosing structures are proposed.

In accordance with SP 385.1325800, during the reconstruction of facilities of an increased and normal level of responsibility, their protection against progressive collapse should be ensured. However, studies devoted to the resistance of reconstructed structural systems subjected to sudden structural transformation are practically absent in the scientific literature. In connection with this the subject of research in this article is the resistance to the progressive collapse of the reinforced concrete frame of the reconstructed industrial building with reinforcing elements made of steel rolling profiles. It is shown that with a greater initial flexibility of compressed-bent elements, a scenario of exhaustion of the bearing capacity associated with a buckling is possible. In this regard, it is proposed to use a nonlinear calculation of the stability of the deformed states of the structural system as an additional tool in assessing the resistance of building frames and structures to progressive collapse.

Russian Federation Federal Law No. 384-FZ "Technical regulations on the safety of buildings and structures" contains requirements for ensuring the mechanical (structural) safety of structural elements of structures at the stages of design, manufacture, construction and operation. Quantitative measures of mechanical (structural) safety are reliability, risk, survivability, etc. The article considers the new algorithm for design load-bearing structural elements based on the reliability index for one or more limit state criteria with limited statistical data. Examples of design of the load-bearing element using the probabilistic method are given. The method is based on the provisions of the possibility theory and fuzzy sets theory. As a measure of reliability, the necessity N and the possibility R of non-failure are used. The proposed approach to the order (algorithm) for load-bearing elements design has an advantage over the known traditional approach since it reduces the design time and, accordingly, the costs. The proposed algorithms for structural elements design for a given reliability level can be used when selecting cross-sections of load-bearing elements of structures according to the limit state criteria of the first and second groups with the specified reliability level, in particular, with limited statistical information about the controlled parameters, which will ensure compliance with the requirements of GOST 27751-2014.

Results of experimental investigations of deformation, crack resistance and bearing capacity of multi-storey monolithic reinforced concrete frames reinforced by indirect reinforcement at their static-dynamic loading caused by sudden hypothetical removal of one of the columns are presented. According to the experimental data, diagrams "moment - curvature" and "load - crack opening width" are built under the considered two stage loading mode: the obtained results allowed to estimate dynamic loading in frame elements (static - at the first stage and dynamic - at the second stage). Comparison of experimental parameters of the diagram for structures of frames reinforced by indirect reinforcement and frames without indirect reinforcement shows that the use of indirect reinforcement in addition to conventional rod reinforcement increases the survival of the structural system under special effects and can be considered as one of the ways to protect reinforced concrete frames of buildings from progressive collapse.

The article addresses the problem of standardizing comfort and safety of the city’s living environment as an effective mechanism for regulating the anthropogenic impact on the environment. A review of publications was carried out, as well as an analysis of the experience of developing the Russian regulatory framework affecting scientific and technical issues of ensuring the safety and comfort of the city’s living environment. A classification is presented and an analysis of the requirements contained in various legal, regulatory and methodological documents, as well as standards of quality of living, is carried out. A review of the methodological documents on the assessment of the quality of the living environment of the city. The conclusion is drawn about the need to create a full-fledged, not fragmented structure of technical regulation of capital construction and spatial arrangement of the territory, corresponding to its social significance and the degree of influence on the development of the country's economy, content and organization of work in this field of activity. The research results can be used in the development of the future code of rules “A comfortable and safe living environment of the city. General positions.”