Introduction. The limit state method is the primary tool in both domestic and international design practice; however, its “semi-probabilistic” nature does not allow for an explicit consideration of the distributions of random variables. At the same time, the use of probabilistic methods, such as the First-Order Reliability Method (FORM), provides a more objective assessment of safety. Particular attention is drawn to the lack of a clear quantitative specification of the target reliability index β in Russian design codes, which complicates the evaluation of the safety of adopted design solutions.

Materials and methods. The study was carried out on the example of a steel beam operating as part of an office building floor system. Two modern approaches were applied for the analysis: the limit state method (Level I) and the First-Order Reliability Method (FORM, Level II). The input data included the beam’s geometric characteristics, material densities, and the statistical properties of loads.

Results. Calculations based on the limit state method confirmed compliance with strength requirements, with a utilization factor close to unity. The application of FORM made it possible to determine the statistical parameters of the limit-state function, the probability of failure and survival, and the corresponding reliability index, β = 2.332. Comparison with calculations according to European standards revealed stricter requirements: when considering the statistical properties of loads according to JCSS, the required section modulus increases by 27 %, and the reliability index reaches β ≈ 2.943. Neither approach achieved the normative level of β = 3.8 specified in EN 1990 for RC2 class structures.

Conclusions. A significant divergence in reliability assessments was identified when comparing deterministic limit state calculations under Russian and European standards. The reasons for these differences (distribution models, load parameters, and code factors) were highlighted. The study emphasizes the need to improve national approaches to structural reliability. Promising directions for further research include refining distribution models for strength and load characteristics, as well as developing simplified engineering methodologies for the application of probabilistic methods in design practice.

Introduction. Modelling of geotechnical systems faces the challenge of inaccuracy and incompleteness of data about the system being modelled. Existing deterministic methods for foundation design do not allow for a quantitative assessment of risks associated with the spatial variability of soil properties. The aim of this research is to demonstrate the application of a probabilistic-stochastic approach based on the Random Finite Element Method (RFEM) for assessing the reliability and risk of exceeding allowable settlements of the foundations of a temple complex in Moscow.

Materials and methods. The study used engineering geological investigation data obtained by electric-contact dynamic sounding (ECDS) to analyze the spatial heterogeneity of soil mechanical properties. Two approaches were used to predict the final precipitation of the base: deterministic calculation using the layer-by-layer summation method and numerical modelling using the finite element method in OPTUM G2. Stochastic analysis was performed using the Random Finite Element Method (RFEM), in which the spatial variability of soil parameters is determined using random field theory. Vertical and horizontal correlation distances, as well as coefficients of variation for the deformation characteristics of the soil, were defined for each engineering-geological element.

Results. Deterministic calculations using the layer-by-layer summation method showed settlements in the range of 22–51 mm, not exceeding allowable limits. However, numerical modelling using FEM revealed significantly larger settlements (56–118 mm, depending on the assumed deformation modulus of the fill soils). Probabilistic analysis demonstrated that with a fill soil deformation modulus of 5 MPa, the probability of exceeding the limiting settlement for Foundation I is 61 %, and for Foundation II, 23 %. A high probability (approximately 9 %) of the occurrence of inadmissible differential settlement between Foundations II and III was established.

Conclusions. It is shown that traditional deterministic calculation methods may fail to identify potentially hazardous foundation performance scenarios. The application of stochastic methodology (RFEM) allows for a quantitative assessment of foundation reliability and the risks of exceeding limiting deformations. The implementation of modern calculation methods requires refinement of the regulatory framework, particularly regarding the methodology for determining the depth of the influence zone and the processing of field test data considering the spatial variability of soil properties.

Introduction. In combined arch systems, supports are often hinged to prevent moment transmission to underlying structures. For combined arch systems, support options include either hinged supports on both sides, or hinged supports on one side with a lower tie to support thrust. This paper analyzes the advantages and specific features of both support options using the stress-strain analysis of an arch with radial ties.

Materials and methods. The comparison was conducted using a preliminary theoretical study and subsequent numerical calculations. The calculation models were implemented in the SCAD finite element software package, taking into account the geometrically nonlinear nature of the structure’s operation. Tension forces in the tie rods were selected using a previously published algorithm.

Results. Based on the results of experimental studies and numerical calculations, stresses and displacements in arch sections were obtained. The movements of the circuit, graphs of correspondence between experimental data and calculation results are shown. Directions for improving experimental models of such combined systems with ties are analyzed.

Conclusions. A comparison of a combined arch system with two fixed hinged supports and an arch system with a single hinged movable support and a lower tie revealed that the horizontal and vertical displacements of the arch chord are several times greater in the arch with a movable support. After selecting and redistributing the prestressing forces in the ties, the resulting longitudinal and transverse forces in the chords of both arches are comparable, but the bending moment in the arch with a movable support is half as strong. In terms of the required metal content for the chord, both arches require virtually the same amount of steel. However, in terms of the required metal content for the tie rods, the arch with a movable support requires one and a half times more material, as greater tensioning force is required for the tie rods. If there is no bottom tie rod, and the arch thrust is supported by other supporting structures, it is advisable to use arches with fixed supports. If this is not possible, an arch with a bottom tie rod and one movable support should be used.

Introduction. The subject of the study is the determination of parameters for a physically nonlinear computational model of steel fibre-reinforced concrete (SFRC) to be used in the numerical analysis of the stress state of precast tunnel lining segments subjected to loads transmitted by tunnel boring machine (TBM) thrust jacks during TBM advance. The relevance of the study is related to the need to account for the post-cracking behaviour of SFRC under localized jack forces. Although residual tensile strength parameters obtained from standard three-point bending tests, R0.5 and R2.5 (GOST R 59535, EN 14651), are available, a practical procedure for converting these parameters into inputs for nonlinear constitutive models is not specified. The aim of this work is to develop a procedure for determining the tensile strength ft and the tensile fracture energy Gt for the Concrete Plastic Damage Model (CPDM) based on standard test results.

Materials and methods. The study uses results of three-point bending tests on notched beam specimens with crack mouth opening displacement control, characterized by residual tensile strengths R0.5 and R2.5. An inverse numerical analysis was performed: the tests were simulated in ZSoil using the CPDM constitutive model; a series of parametric analyses was carried out by varying ft and Gt; and regression analysis was applied to establish functional relationships between the model parameters and the residual tensile strengths of SFRC.

Results. The influence of ft and Gt on R0.5 and R2.5 was quantified, regression relationships were obtained, and nomograms were developed for determination of CPDM parameters from test data. The procedure was verified and further applied to the analysis of a tunnel lining segments under localized loading from TBM thrust jacks, demonstrating an adequate reproduction of the cracking process while accounting for the residual tensile load-carrying capacity of SFRC.

Conclusions. The proposed approach enables practical determination of CPDM parameters from standard SFRC tests and can be used in the design and structural analysis of tunnel lining segments subjected to localized concentrated loads from TBM thrust jacks.

Introduction. This study investigates the seismic performance of high-rise buildings using the linear response spectrum method (LRSM). Six buildings of different heights with a frame–shear wall structural system are considered. Natural frequencies and vibration mode shapes were determined, along with contour plots of internal forces and displacements and maps of required reinforcement. The variation of the stress-strain state of the main load-bearing elements depending on the number of storeys and support conditions was analyzed. The limiting number of storeys for the considered structural system under seismic action with an intensity of 9 according to the MSK-64 scale was determined. The influence of increasing building height and foundation stiffness on the dynamic characteristics of the structures was also evaluated.

Materials and methods. The study considers six monolithic reinforced concrete buildings of different heights with a frame–shear wall structural system and different support conditions. The structural analysis was carried out using the linear response spectrum method. The calculations were performed in accordance with current seismic design codes for buildings constructed in seismic regions.

Results. The results made it possible to obtain a quantitative assessment of the applicability of the frame–shear wall structural system for buildings within the considered height range. The influence of the number of storeys and foundation stiffness on the distribution of internal forces, lateral displacements, and the required reinforcement of vertical load-bearing elements was identified.

Conclusions. The obtained results may be used to develop recommendations for selecting structural systems, determining rational cross-sections of vertical load-bearing members, and assessing the permissible height of buildings constructed in seismic regions.

Introduction. There are currently a large number of brick buildings in use, the plastered facades of which require periodic repair. This paper examines the problem of the insufficient durability of façade cladding, as it often ceases to be serviceable well before the end of the specified intervals between repairs. One of the key causes of premature deterioration of the finish is the incompatibility of the technical properties of the brickwork, plaster, and paint layers, which manifests as the compositional instability of the material system under the influence of cyclic climatic factors. Implementing a comprehensive approach in formulating requirements for finishing, which define the operation of facade materials and the base as a single system, appears to be one of the most important directions for solving the stated problem. The main objective of the research is to justify the criteria and method for selecting finishing systems based on ensuring chemical and physico-mechanical compatibility of materials, taking into account the operating factors affecting them. The article considers the first stage of the study, which consists of experimentally determining the extent to which the type of binder in plaster mortars, as well as the presence of primer and paint components in the system, influence one of the key criteria for choosing a finishing system — the vapour permeability.

Materials and methods. The critically important criterion of compatibility between finish and base is the comparability of vapour permeability values. The study presents results on the vapour permeability of plaster finishing systems that differ by the type of binder and by the methods used to prepare the surface for painting.

Results. It is shown that applying finishing plaster layers instead of putty increases vapour permeability and achieves values characteristic of brickwork. It was found that the use of a hydrophobic additive in silicone paint does not significantly affect vapour permeability, which may be used, if necessary, for systems with water-repellent properties.

Conclusions. A methodology for selecting materials for plaster facade finishes of brick buildings based on a comprehensive assessment of compatibility is proposed. Preliminary recommendations for selecting finishing systems based on the vapour permeability criterion are developed, aimed at increasing facade reliability and reducing repair costs.

Introduction. The study aims to develop and optimize the composition of a four-component binder using locally sourced raw materials from Iraq. The goal was to create a mathematical model describing the influence of variable factors — additive component ratios — on key output parameters: compressive and flexural strength at 28 days of age.

Materials and methods. The materials used were Portland cement CEM I 52.5 N, metakaolin (MK), fly ash (FA) from brick production, and date kernel ash (DKA). The latter component is of particular interest for waste management in the region. Beam specimens were prepared from mortar using standard methods. To optimize the composition, a rotatable central composite planning (CCP) method was used, allowing the construction of second-order multiple regression equations.

Results. As a result, adequate regression models were obtained linking flexural Rbend and compressive Rcomp strengths with two factors: the ratios of FA/MK and DKA/MK. The analysis showed that maximum strength is achieved with a partial replacement of cement (10 % of the mass) with a mixture of active mineral additives. The optimal ratio of components in this mixture is MK:FA:DKA = (55–60):10:(30–35).

Conclusions. It was found that the best mechanical properties (compressive strength of 72.4 MPa and flexural strength of 7.58 MPa) are demonstrated by a composition consisting of 90 % Portland cement, 6 % metakaolin, 1 % fly ash, and 3 % date kernel ash. Thus, the study confirms the feasibility of effectively using local industrial and agricultural waste from Iraq to create a high-strength multi-component binder.

Introduction. In most Russian cities and settlements, there is a lack of centralized surface wastewater (SWW) treatment systems, which makes it necessary to improve the technological reliability of local SWW treatment facilities.

Materials and methods. The analysis of design and passport data and the practice of operation of a number of local wastewater treatment facilities in the city of Moscow, the study and modeling of the process of wastewater treatment by the filtration-sorption method on a laboratory installation and a pilot plant (PP) with loading of various filter materials in different modes and dynamic conditions on real wastewater formed in residential areas, highways, and industrial zones in Moscow.

Results. Full-scale and experimental studies have shown that the technological solutions and designs of such installations have a number of significant drawbacks. The declared degree of purification of the SWW by the residual content of only three pollution indicators is insufficient to obtain permission from environmental authorities to discharge treated wastewater into water bodies. An improved technological scheme for the purification of the SWW has been developed, which uses a new flow-type pre-treatment unit for the SWW made of glass composite materials, for which a utility model patent RU 207418U1 “Device for Purification of Surface Wastewater” has been obtained.

Conclusions. The local flow-through SWW purification systems currently being designed do not comply with the design standards in force in the Russian Federation and do not meet the regulatory requirements for the degree of SWW purification established by environmental and water legislation. The studies conducted at the PP confirmed the functionality of the laboratory setup and the selection of media and reagents, and showed that the concentration of SWW after post-treatment on filters with various media corresponds to the maximum permissible concentrations of pollutants in a water body of fishery importance, as well as to Sanitary rules and regulations 1.2.3685–21.

Introduction. The results of the study of modified polymer ultrafiltration membranes used to separate stable emulsions of process waters of circulating water supply cycles, pipe and electric welding shops, and the heat-generating assembly of a metallurgical enterprise are presented.

Materials and methods. Experiments on filtration of wastewater containing colloidally dissolved and suspended impurities of petroleum products were carried out while maintaining a constant filtration pressure of 0.2 MPa. The filtering mode is dead-end. Before each series of experiments, the emulsion was injected with coagulant in prescribed doses. The filtration process was performed using a laboratory filtration cell. A hollow fibre ultrafiltration membrane made of polyvinylidene fluoride was used as a filter element. To increase hydrophilicity, the membrane surface was subjected to a two-stage modification with sequential treatment with solutions of tannic acid and potassium permanganate in buffer solutions with different pH values.

Results. It was found that the modified membranes provide a high degree of removal of petroleum products and organic compounds that determine the COD value. The optimal coagulant dose was determined to be 20–25 mg/L of Fe3+, at which the minimum content of petroleum products (up to 0.2 mg/L) and COD (up to 190 mg/L) in the filtrate is achieved. The specific productivity of the membranes was 17–12 L/(h·m2) at coagulant doses of 5–25 mg/L. A further increase in the coagulant dose is not advisable due to the lack of significant improvement in treatment efficiency and the increase in reagent costs.

Conclusions. The results obtained confirm the promise of using modified ultrafiltration membranes for the removal of emulsified petroleum products during wastewater treatment and post-treatment.

Introduction. The most promising of the rapidly developing energy-saving technologies used in life support systems is the regulation of ventilation system performance depending on the indoor air quality in the serviced rooms. In the process of regulation, transients occur, accompanied by fluctuations in indoor air parameters. The study of the patterns of development of transient processes in the air flow is necessary for the design of energy-efficient elements of climate systems, the development of adaptive algorithms for climate control. Experimental data on changes in the parameters of air flow and heat in the “heater – fan – room” system with stepwise sequential control of fan performance are presented and analyzed.

Materials and methods. The method of studying the process of heat exchange between air, a climate control system and a serviced room is based on a field experiment carried out in a building in actual operation. The air flow parameters in the system under study were recorded as for a system with concentrated parameters.

Results. At different time intervals between step changes in fan performance and for different modes of operation of the air heater, transient processes of changing air flow parameters have been experimentally investigated and studied.

Conclusions. The minimum duration of the transient process of changes in the parameters of the air flow passing through the climate control unit is achieved with a certain optimal value of the time interval between fan performance spikes.

Introduction. The paper notes the relevance of the concept of a deterministic model of organizational and technological reliability of construction (DM OTR) for the development and exploration of the Arctic region in Russia. The methods of developing the DM of OTR are presented. Including engineering formulations of definitions of key concepts, the goals of developing the DM of OTR, the application of the method of describing organizational and technological reliability (OTR) from the standpoint of the general theory of systems is shown, the DM of OTR is structured into mathematical and engineering parts, the connection of the DM of OTR with information technologies is considered.

Materials and methods. When describing the OTR as a system, its influence on the result of the construction period of the investment project is clearly shown. The engineering part of the DM OTR is described as a method of coordinating the performers of the organization and management of construction production in solving technologically and organizationally related tasks of performing technical processes in the design marks of a capital construction project and their resource provision. The practical basis of the engineering part of the DM OTR in the article is the standard scheme of coordination of performers, algorithmically connected with the mathematical part of the DM OTR.

Results. Results of the research carried out within the framework of the article are presented in the form of a system of symbolic expressions of the characteristics of the OTR system, an analysis of the properties of special spherical functions of higher mathematical analysis in relation to the topic of the article, in the form of a table of the staffing scheme for coordinating the solution of production problems the corresponding simulation model of the functioning of the engineering part of the DM OTR, in turn parametrically connected with the mathematical part of the model, as well as in the form of a comparison table of the operational characteristics of various platforms for the development of special software and communication support for the functioning of the DM OTR.

Conclusions. Conclusions were made that the use of DM OTR will allow for timely prediction and elimination of unfavorable production trends. The development of the DM OTR is promising, with a medium-term duration, complex, carried out by specialists of various specialties: technology of construction of buildings and structures, organization of construction production, management of construction production, management of production activities of the enterprise, as well as IT specialists.

Introduction. The paper presents the results of a study of the life cycle of multifunctional construction facilities, taking into account their functional specifics. The scientific problem of the study is the discrepancy between the existing methods of managing projects for the construction of multifunctional facilities and modern requirements for the quality and effectiveness of their implementation within the framework of the theory of life cycle management. The object of the research is organizational and technological solutions implemented within the framework of end-to-end processes through the stages of design, construction and operation within the life cycle. The subject of the research is a set of criteria for assessing the quality of decisions made: cost, reliability, adaptability and functionality. The purpose of the research is to develop a multi-criteria evaluation system for a set of organizational and technological solutions for managing key end-to-end processes of the multifunctional facility’s life cycle.

Materials and methods. A database of organizational and technological solutions related to the stage of the life cycle of a construction facility and the type of end-to-end process was proposed as research materials. The developed mathematical model for selecting and evaluating design solutions based on the matrix data processing method allows for a comprehensive analysis of the effectiveness of a construction project during the life cycle of a multifunctional facility.

Results. The research results include: a database of organizational and technological solutions for end-to-end processes throughout the life cycle of a multifunctional construction facility, a mathematical model for selecting and comprehensively evaluating design solutions, and a practical life cycle management tool based on comparing different scenarios for organizing life cycle stages and selecting optimal solutions based on cost and technological characteristics.

Conclusions. The scope of the assessment tool lies in setting the task of optimizing the cost and technical characteristics of the life cycle management scenario of a multifunctional facility. The optimal choice of technologies, materials, and planning solutions reduces construction and maintenance costs, and increases the durability and comfort of buildings.

Introduction. The relevance of the topic under study is determined by the fact that transport logistics is directly involved in providing enterprises, including the construction sector, with material flows and the sale of finished products, and economic growth, the country’s defense capability and the quality of life of the population depend on the effectiveness and balance of this type of logistics. Most of the imposed sanctions represent serious economic and political pressure.

Materials and methods. The study of container shipping analysis in Russian ports used data from official statistical reports and publications in the field of logistics and transport. The research methods used were quantitative analysis, comparative analysis of the dynamics of cargo flows along various routes and types of transportation.

Results. The study examines the main types of sanctions, their impact on the country’s transport system and its consequences for the economy, and identifies new trends in logistics activities, and also proposes measures to reduce the negative impact of anti-Russian sanctions, such as optimization of transport infrastructure, active support of private initiatives and the development of new models of logistics interaction. Particular attention is paid to the reorientation of logistics activities from Europe to the countries of Central, East and South Asia. Emphasis is also placed on the further development of domestic software and the integration of new technologies to improve the efficiency of logistics.

Conclusions. The need to create a reliable logistics system to ensure the economic growth of the country and its investment and construction sector is becoming critically important, especially in the context of the reorientation of cargo flows to the East. New logistics involves the use of proxy states and proxy buyers, which creates new economic challenges and opportunities.