The relevance of this work stems from the absence, in current regulatory documents (SP 63.13330.2018), of methods for accounting for the restraining effect of reinforcement on concrete creep. This omission can lead to a significant overestimation of design deformations and an inadequate assessment of structural stiffness under long-term loading.

A series of 62 specimens of six types was manufactured and tested: control concrete prisms, prisms with internal bar reinforcement, and steel-concrete prisms with external steel plate reinforcement. The latter were produced in three configurations, differing in the length of the tie rods and the presence of transverse ties, as well as steel-concrete web-type specimens. The testing program included both short-term tests until failure and long-term tests under two stress levels (0.3 and 0.5 of the ultimate load) under uniaxial and biaxial compression. It was recorded that, for the same reinforcement ratio, the creep deformations of specimens with internal bar reinforcement were, on average, 20% higher than those of specimens with external plate reinforcement at a stress level of 0.3. When the stress level was increased to 0.5, this difference grew to 25%. Under biaxial compression of the web-type specimens, longitudinal creep strains decreased by 25% compared to the uniaxial compression regime, demonstrating an additional reserve in the deformability of structures operating within closed contours. The obtained data indicate that neglecting the restraining effect of reinforcement in design codes can lead to an overestimation of creep coefficients by a factor of 1.5 to 2 for reinforced concrete elements, and by up to a factor of 3 for steelconcrete composite structures under biaxial compression. The study substantiates the necessity of a differentiated approach to accounting for the influence of reinforcement, depending not only on its ratio but also on its type (bar vs. plate), bar diameter, and the stress-strain state of the element. Directions for improving the current regulatory framework are proposed.

The article addresses a pressing issue of limiting crack formation in semi-sleepers designed for tracks with reduced vibration. As an effective design solution, the use of steel-fiberreinforced concrete (SFRC), which possesses enhanced strength and deformation characteristics, is proposed. The study, conducted in two stages, involved experimental methods on full-scale specimens and numerical modeling of the stress-strain state. The results established that the steel-fiber-reinforced concrete semi-sleeper surpasses the traditional reinforced concrete one in load-bearing capacity by 198%. Furthermore, a multiple increase in crack resistance was observed: resistance to the formation of normal cracks increased by 300%, and to inclined cracks—by 679%. The obtained results confirm that the application of steel-fiber-reinforced concrete not only allows for meeting stringent regulatory requirements for crack resistance but also significantly enhances the overall reliability and durability of the structure under service conditions.

An approach is proposed for area-wide protection of buildings and structures from surface seismic waves using a seismic barrier in the form of an above-ground liquid storage tank placed on the surface of an elastic half-space. A mathematical model of the interaction between surface waves and the seismic barrier is developed, accounting for contact conditions at the interface between media and the weak compressibility of the fluid. A dispersion relation is obtained for Rayleigh waves beneath a finite-thickness liquid layer, which correctly reduces to the classical limiting cases of no fluid, infinite depth, and an incompressible fluid. For a barrier of finite length, based on continuity conditions at the lateral boundaries, the Rayleigh-wave transfer function T_R is derived and analytical approximations are proposed. Resonances kL=nπ, corresponding to no attenuation, are identified, along with zones of exponential suppression between them; the magnitude of the suppression is governed by a parameter α_f, proportional to the added mass of the fluid and dependent on the ratio of velocities. It is shown that for Love (SH) waves the liquid barrier provides no shear stiffness and does not produce attenuation, necessitating alternative solutions for area-wide seismic protection. Contour plots of the transfer function are presented to support preliminary design choices of the tank height and length needed to achieve a specified level of Rayleigh-wave attenuation.

In the current Russian framework for limit state design, partial safety factors are commonly calibrated for a reference service life (typically 50 years) and a conventional set of uncertainties. Modern practice increasingly involves temporary, modular and transformable facilities, as well as service-life extension of existing structures, where a consistent adjustment of target reliability and local safety factors to a specified service life is required. This paper reviews contemporary probabilistic concepts used in structural reliability and code calibration (Eurocodes, JCSS, ISO 2394 and service-life design). Based on R&D results obtained at NRU MGSU, an engineering procedure is proposed to map a reference reliability level to a target service life T by (i) converting the accepted total failure risk over the reference period into an equivalent annual target reliability index and (ii) adjusting local partial factors for actions and resistances using sensitivity factors from FORM under a lognormal representation of basic variables. The approach indicates that for variable climatic actions (snow, wind) the design partial factor γf may be reduced by approximately 10–20% for T≈10–15 years while keeping the accepted total risk over the service life constant; for permanent actions and resistance factors γm, the correction is usually minor. A step-by-step algorithm and an illustrative calculation example are provided.

This study presents a semi-inverse method for determining stresses in a rectangular cantilever beam using algebraic polynomials of a function. A 3rd degree polynomial was chosen as a stress function, the coefficients of which are determined based on the boundary conditions of the problem. To determine the displacements, Hooke's law was adopted, from which deformations were expressed through displacements using the Cauchy formulas. The influence of shear deformations on deflections and buckling of the cross section under direct bending was studied. It has been established that for beams with a ratio of cross-sectional height to span h/l <1/5, the influence of shears on the deformed state of >the beam is insignificant. We also carried out a comparative analysis of the analytical calculation results with the results of numerical modeling in the Lira CAD software package.

Under current conditions, the fire resistance assessment of building structures cannot be limited to the use of the standard time–temperature fire curve, since it does not reflect the transient and spatially non-uniform thermal exposure inherent to real fires. This paper describes the use of the Abaqus software package to analyze the behavior of reinforced concrete structures under real-fire conditions, enabling numerical simulation within a coupled thermo-mechanical framework. A numerical model of a reinforced concrete floor slab is presented on the basis of the adopted physical model of an existing structural frame, including the definition of geometric parameters, the thermophysical and mechanical properties of concrete and reinforcement, and the thermal loading conditions. The main objective of the study is to verify the correctness of the input data specified in the numerical model and to substantiate the feasibility of further investigations based on it. Model validation is carried out by comparing the results obtained from analytical and numerical solutions of the heat-transfer problem; the acceptable agreement achieved in this comparison confirms the correctness of the adopted numerical model and supports its further application for analyzing the thermal effects of real fires on reinforced concrete structures and assessing their fire resistance.

Territorial planning and urban design are a set of measures to ensure the sustainable development of cities and megacities today. Issues related to adaptation to climate change in the context of global warming are reflected in city master plans in a one-sided manner, based on analyses of the natural and climatic conditions of specific areas. Adaptation and mitigation measures are reflected in city adaptation plans or climate safety passports. Integrated development of territories is a highly effective tool for creating a comfortable living environment. The purpose of the study is to develop a methodology that ensures a balance between adaptation and mitigation in the integrated development of territories. The territory of the city of Rostov-on-Don was chosen as the object of the study. The methodological toolkit selected for this purpose is an adapted methodology for integrated land assessment, which interconnects diverse information about the state of urban territories. The need to select measures to reduce the negative impact of climate change is substantiated. The step-by-step implementation of the methodology is demonstrated on the example of a project for a general education institution building located on the territory of integrated development in the city of Rostov-on-Don.

The integration of additive technologies into the construction industry is driving a technological renewal of the entire building sector. Construction 3D printing is creating a fundamentally new approach, not only to manufacturing processes but also to architecture itself, unlocking unprecedented new possibilities. With significant potential for process optimization and reducing material consumption, additive manufacturing opens up prospects for the sustainable development of high-performance construction. Despite the growing interest in additive technologies, the issues surrounding their comprehensive assessment and optimal application require further study. A systematic analysis of the thermal performance characteristics of building structures created by 3D printing methods is becoming particularly relevant. This article addresses the pressing problem of optimizing building structures constructed using additive manufacturing methods. Despite the increasing prevalence of 3D printing in construction, a comprehensive investigation into the relationship between geometric parameters, thermal performance characteristics, and material consumption remains insufficiently studied. The aim of this work is to evaluate the influence of key geometric parameters on the operational performance and resource efficiency of building envelopes. The study employed a comprehensive methodology combining parametric modeling with subsequent thermal performance analysis. Three different configurations of wall elements with sinusoidal geometry were examined, varying in wall thickness and the number of sinusoids. The practical significance of this work lies in developing design principles for optimizing building structures intended for additive manufacturing, enabling a simultaneous reduction in material consumption and improvement in energy efficiency. The results obtained are valuable for the further development of sustainable construction and the optimization of resource consumption in the building industry.

The development of cement mixtures to enhance the quality of construction is a major focus in the field of building materials research. Based on an analysis of existing literature, the use of carbon-based additives to improve the properties of cement pastes is contradictory and strongly depends on the availability of the additive and the technical specification. Moreover, the mechanism of interaction of a carbon modifier with binding materials is described. The mineral and phase composition of the standard grouting Portland cement used is presented. The article considers the effect of a fullerene soot additive on the structural and rheological properties of cement paste. The X-ray phase content of the modified cements revealed the absence of chemical interaction of the carbon additive with the cement hydration products. The analysis of the physical and mechanical tests showed an increase in the strength of the cement stone during curing at normal and moderate temperatures. Computed tomography was used to calculate the parameters of the pore volume and porosity of the samples. As a result, the optimal concentration of fullerene additives was established to enhance the characteristics of the cement composition. The presented study proposes one of the possible solutios to the challenge of developing a grouting material that enhances the tightness and longevity of wells.