The stress values at the crack tip in bending reinforced concrete beams are considered. The stress state is analytically determined with an initial and propagating crack. Equations of the equilibrium of a part of the beam cut along the crack line are compiled. These equations are reduced to a system of two nonlinear algebraic equations using the plane-sections hypothesis. The equations determine the stress zone’s height and the nominal stress at the crack tip for a beam with an initial crack and the crack length. The rest of the stress state parameters are expressed regarding the zone stress height and the nominal stress or crack length. The same equation system determines the external moment starting from which the crack length increases. The analytical method for determining the stress intensity factor (SIF) with an initial and growing crack in bent reinforced concrete beams is proposed. The method is based on the assumption that the size of the stress concentration zone at the crack tip is determined by the equality of the nominal and local stresses at the end of this zone. The method determines the value of the external moment starting from which the crack length increases. The stress zone’s size is determined by the coincidence of the local stress with the nominal stress. The same problem is solved in a three-dimensional formulation by the FE method, considering the stress field’s peculiarities at the crack tip. The calculation results coincide with the analytical solutions.

Scientometric analysis using the Scopus database and VosViewer program identified the critical directions of development of this or that field to identify promising technologies and to understand how these achievements affect the practice of design and construction. According to the analytics, the average number of articles per year on the topic of structural fire resistance and flame retardants increased by 18% compared to the previous period, and according to preliminary data, the trend will continue in 2024. Among the most cited papers, studies on composite materials and polymers dominate. Among the most productive researchers in the field of flame retardancy of materials are Hu, Yuan (54 papers), Wang, WeiYong (47 papers), and Jiang, Jian (39 papers). According to Scopus, research papers on this topic have been published in 2175 sources. The leading journal in terms of the number of published papers is Fire Safety with 250 publications, but journals such as Fire and Buildings of MDPI Publishing are strongly increasing the pace. Chinese researchers are actively studying various aspects of fire resistance of materials and have published 40% of all papers. Keyword analysis revealed a lack of papers on calculation of fire resistance of structures with fire protection means, calculation of fire resistance of composite structures, and 3D-printed structures compared to the number of articles on the reliability (strength calculation) of building structures.

The creep of concrete is one of the main problems threatening concrete structural development and the stability and safety of structures. However, the nonlinear theory is the key to solving the problem of taking into account the physical and mechanical properties of concrete creep in shell structures. To create such a theory, the original shell is replaced by a continuous equivalent elastic shell. To determine the stress–strain state of the structure, the equations of nonlinear creep and crack growth are derived, and a deformation model of the section is created. The behavior of the structure at all stages of the life cycle is investigated by solving the solving systems of differential equations of equilibrium, motion, and perturbation of the equivalent shell. The values of the ratios of dependence of long-term and short-term critical loads on deformations, forces, cracks, etc., are given. The accuracy of the solution of the developed nonlinear theory is compared with the linear theory of concrete creep as well as experimental data. The results show that, according to the linear theory, for the values for the short term and long term, up to 56% and up to 39% of critical loads are overestimated, respectively. The creep process in practical engineering can be effectively controlled by the results of the proposed theory.

The results of studies on solid fuel quality control by neutron gamma radiation spectrometry of the inelastic scattering of fast neutrons on carbon and the

The operation of reinforced concrete wall panels with holes used in civil engineering has been studied. Under conditions of plane stress wall panels operate in vertical (q_y) and horizontal (q_x) evenly distributed loads conditioned by the own weight of the panels and pressure of the overlying overlap and covering structures. The effect of wind load on the building develops the flexural state of wall panels, i.e. loading the structures with the transverse evenly distributed load takes place. To study the stress-strain state of the above-mentioned structures, the work proposes a rod approximation in the form of a rod of a step-variable cross section, taking into account the presence of a hole in the body of the wall panel. Using the numerical finite-difference method there one solved the initial fourth-order differential equation for the compressed-bent state of the deformed rod. The results are presented in the form of the diagrams of transverse, axial and angular displacements, bending moments, longitudinal and shear forces diagrams. The results of the studies are of scientific and practical importance.

Studying the causes of accidents allows avoiding mistakes in the design, construction and operation of the building. According to the results of a continuous visual and detailed instrumental examination, the materials are collected and analyzed in the article that characterize the causes of the accidental collapse of the overlapping section of the metal frame. The calculation of steel beams of the overlapping section in the “2-3/B-V” axes at the + 4,500 mark of the overland parking building was performed in the LIR-STC design system of the LIRA-CAD 2013 program both for design combinations of efforts and for design combination of loads. Design errors that led to the accident are identified. Both the results of the calculation of the bolted connection, and the calculation of steel profiled flooring are presented. In addition, technical decisions are made on the further safe operation of the facility. This accident draws attention to the problem of ensuring safety of buildings and structures and the need for an integrated approach in the framework of industrial safety expertise.