STRENGTH ASSESSMENT OF STEEL-REINFORCED CONCRETE STRUCTURES OF THE BOOK DEPOSIT OF THE NATIONAL LIBRARY OF THE REPUBLIC OF BELARUS

As a city is a complex system, it complies with the principles pertaining to organization and management of systems. System analysis makes it possible to figure out the difference between managing systems (subject) from systems that are managed (object). There is a link between these system formations which unites them in a common system. Such relationship is a source of information for development of management action. Impact on the system is achieved through availability of influential means and data. Urban planning science represents a city as a complex of socio-economic, territorial-productive and demographic-ecological systems of the following type: “population” – “environment” – “activity”. “Environment” is thought of as a technical system with such synonyme notions as “urban planning system”, “anthropogenic environment”, “settlement system”. “Environment” has two components – territory and buildings. Ukrainian legislation determines that management of urban planning activities is carried out through developing urban planning documentation and carrying out urban planning monitoring. Results of the urban planning monitoring are taken into account while preparing urban planning documentation (introduction of amendments to it) and programs of socio-economic development. Thus, urban planning monitoring represents a management system of urban planning activity in the Ukraine. Legislation of the Republic of Belarus contains some provisions which regulate urban planning activity through urban development planning and zoning of territories; creation and maintenance of urban planning cadastre; control over development and implementation of urban planning, architectural and construction projects; implementation of state construction supervision. Data of the urban planning cadastre are taken into account in urban planning documentation. In comparison with the Ukraine management of the urban planning system in the Republic of Belarus is attached to the urban planning cadastre. The urban planning systems of the Ukraine and the Republic of Belarus are self-managed reflexive systems that organize their behavior with due account of not only the past experience but also due to possible impact of other system which is in interaction with it.

Analyzes national experience of restoring the old buildings floors. An assessment of the wood-reinforced concrete using experience, steel-reinforced concrete floor structures and methods for calculating load-bearing elements of a composite section is given. It is noted that the current design standards and existing methods for calculating steel-reinforced concrete structures of civil buildings and bridge structures use simplified calculation methods and do not reflect the actual stress-strain state of a bent element, do not take into account the initial pre-operational deformations and stresses, and do not lead to economical design solutions. Sometimes they lead to incorrect results. Expressions of internal moments and forces of steel-reinforced concrete bending elements are presented from the equilibrium conditions of a composite element, taking into account pre-operational forces. The results of our own experiments are presented, where it is shown that during the hardening of concrete, beams and slabs receive deformations in the form of reverse deflection (bending), and internal stresses arise in the sections of steel-reinforced concrete elements. Formulas are given for calculating the deflections of bending elements taking into account their initial deformations. To compare the calculation results of the proposed method for calculating steel-reinforced concrete elements, taking into account the initial deformations and stresses, the data of our own experiments were used and comparisons were given. Satisfactory convergence of the results is shown.

Owing to advancement in advanced manufacturing technology, the reinforcement design of concrete structures has become an important topic in structural engineering. Based on bi-directional evolutionary structural optimization (BESO), a new approach is developed in this study to optimize the reinforcement layout in steel-reinforced concrete (SRC) structures. This approach combines a minimum compliance objective function with a hybrid truss-continuum model. Furthermore, a modified bi-directional evolutionary structural optimization (M-BESO) method is proposed to control the level of tensile stress in concrete. To fully utilize the tensile strength of steel and the compressive strength of concrete, the optimization sensitivity of steel in a concrete–steel composite is integrated with the average normal stress of a neighboring concrete. To demonstrate the effectiveness of the proposed procedures, reinforcement layout optimizations of a simply supported beam, a corbel, and a wall with a window are conducted. Clear steel trajectories of SRC structures can be obtained using both methods. The area of critical tensile stress in concrete yielded by the M-BESO is more than 40% lower than that yielded by the uniform design and BESO. Hence, the M-BESO facilitates a fully digital workflow that can be extremely effective for improving the design of steel reinforcements in concrete structures.

Practical model for predicting corrosion rate of steel reinforcement in concrete structures

The procedure of renovation of damaged concrete matrices by injecting flowing polyurethane compositions is described. It is shown that the process of filling of cracks is accompanied by the penetration of injected compositions into the weakened zones and impregnation of the surface layers of concrete. It is confirmed that the components of polyurethane compositions undergo chemical interaction with the OH-groups of cement stone and mineral fillers of concrete. It is demonstrated that the concrete–transition-layer–polyurethane joints formed as a result of the injection guarantee the required serviceability of concrete structures and buildings. The processes of destruction and failures of concrete and reinforced-concrete buildings and structures are accompanied by the formation and development of deep (often through) cracks in concrete matrices. The aim of the present work is to determine the technological and structural features of hardening and renovation of these objects by the injection filling of cracks and other defects in concrete with polyurethane compositions on the basis of the results of investigations and practical experience [1–8]. The advanced technologies of healing the cracks and defects aimed at the restoration of strength and serviceability of damaged concrete buildings and structures and developed at the Karpenko Physicomechanical Institute of the Ukrainian National Academy of Sciences and the “Tekhno-Resurs Engineering Center” State Enterprise of the Ukrainian National Academy of Sciences are now successfully applied at the plants of the “Energoatom of the Ukraine” National Nuclear Energy Company and Derzhbud of the Ukraine [1, 3, 7, 10]. The technological processes are based on the domestic technique of injection filling of defects in concrete matrices with flowing polyurethane compositions hardening at normal temperatures. In its scientific and engineering level, this technology is in no case inferior to the currently existing foreign achievements in this field [8, 9, 11, 12].

Prestressed Steel Reinforced Concrete (PSRC) Structure is a new system by combining PC technology and steel reinforced concrete (SRC) structure, and is a technical innovation to the conventional structures, such as concrete structures, PC structures and SRC structures. Because having much virtue, for instance high bearing capacity, fine serviceable performance, covering and over loading capability, it will have expansive application. The serviceable performance can be observably improved by putting PC technology on the SRC beams, such as rigidity and crack resistibility degree. Based on static loading experiments of seven PSRC beams with different designing coefficients, the experimental phenomena as loading process, failure pattern are studied, and the primarily influencing factors on flexural performance have been contrasted to educe conclusion for future design.

This article presents the results of the analysis of samples of a machine-shop for the content of organic components and heavy metal ions. The proposed modernized technological scheme uses modern technological solutions for a machine-shop. Based on the analysis of sites and sewage treatment plants of galvanic production, as well as analysis of the presence of polluting components, technical solutions, which are going to increase the intensification and efficiency of water treatment and water treatment through the use of modern physical and chemical methods, technological methods and wastewater treatment devices have been developed. The introduction of additional sorption modules with activated carbon will reduce the ingress of toxic organic components (DBP, aniline, solvents: acetone, gasoline, ethyl acetate, polymer epoxy compounds, including: epoxy adhesives, polymer filler, epoxy-phenolic, phenolic-rubber and rubber adhesives, release adhesives) into wastewater. A modernized scheme using modern solutions will comply with Mosvodokanal standards.
 Keywords: wastewater, water treatment, toxic organic components, heavy metal ions

Purpose The work purpose is to establish the real technical condition of reinforced concrete and steel-reinforced concrete bridges based on the surveys and tests, as well as the analysis and synthesis of scientific and technical sources. Methodology. To achieve the goal, a review and synthesis of scientific and technical sources and regulatory documents regarding the technical condition of reinforced concrete and steel-reinforced concrete bridges and overpasses of Ukraine is carried out. It is shown that the development and implementation of new technologies for repairing the existing bridge defective structures, in particular on the highways of Ukraine is an urgent problem. A thorough analysis of experience and publications on the operation of newly built and long-term specified bridges in the mentioned environments is carried out. The data on the main unacceptable defects and faults of bridge structures as well as the causes, including concrete and reinforcement corrosion, and other defects and faults are presented. The quality indicators of reinforced concrete and steel-reinforced concrete bridge structures are considered, the problems and analysis of ensuring reliability and durability in the operation conditions on the highways of Ukraine are formulated. Results. The analysis of domestic and foreign scientific and technical sources as well as the experience of surveys and tests regarding the technical condition of reinforced concrete bridges structures in Ukraine is carried out. In particular, the analysis and synthesis of the problems of ensuring the reliability and durability of the specified bridges in the operation conditions on the highways of Ukraine is carried out. The design errors, construction defects and faults, and long-term operational faults in the mentioned environments are summarized and clarified. In addition, the obtained data are as the basis to specify the criteria and models of the destruction mechanics in relation to reinforced concrete bridge structures. In particular, based on the obtained data, the methods to determine the VAT and the residual resource of the specified bridges are created. Scientific novelty. Based on the analysis and synthesis of scientific and technical sources and a number of surveys and tests, reinforced concrete and steel-reinforced concrete structures and long-term bridges newly built after the floods in 1998 and 2001, it is possible to summarize the main reasons that significantly affect the structures degradation of both the newly built and long-term bridges. This allows generalizing the design errors, construction defects and faults, and long-term operational faults. In addition, the state data served as the basis to specify the criteria and models of the destruction mechanics in relation to reinforced concrete bridge structures. In particular, based on these data, the methods to determine the assessment of the strength and crack resistance and the VAT and the residual resource of such bridges are created. Practical significance. Based on the given data and observations of real objects for 30 years, the main faults, defects and errors of the design, construction, and long-term bridges are summarized and set up. The methods to determine the VAT and calculate the residual resource, giving an opportunity to work out the repair and restoration method to increase the durability and reliability of long-term bridges are created.

In recent years, the development of urbanization in China has entered a new stage with “quality” as its core. In the process of sustainable urban development, urban planning and construction relics are precious historical warnings and educational resources, and in the stage of accelerated urbanization, social transformation, and industrial upgrading, urban sites face severe pressure and challenges for conservation. This paper presents a summary analysis of various international charters concerning historical and cultural heritage in recent times, and analyzes the urban spatial structure, urban functional zoning, and the differences and evolutionary characteristics of urban construction sites between the pseudo-Manchukuo Xinjing plan and other regions of the world in the same period from a global perspective. The city of Changchun is also used as an example to systematically analyze the existing relics in Changchun using a historical-geographical perspective and spatial analysis methods. The results show that, firstly, the conservation objects of Chinese relics are being enriched and the scope of protection is being expanded, but that there is a lack of protection and utilization of urban heritage and its surrounding environment. Secondly, that the road network system and spatial structure of the pseudo-Manchukuo Xinjing city planning are basically preserved, that the urban green space and functional zoning have been changed, and that the architectural relics show a spatial distribution trend of north-north-east. Thirdly, that the urban functional zoning has been used to construct an urban relics protection area in which three suggestions for the protection of urban relics have been put forward: to establish a holistic protection system for urban planning functional areas; to establish a “district-axis-point” trinity protection model to promote the effective function recovery of urban planning and construction functional areas; and to continue the effective functions of the city. This provides reference for the study of modern urban planning ideas and solutions for current sustainable urban development, upgrading of public service facilities, and green low-carbon urban transformation.

The passivation behavior of steel reinforcements in concrete is significantly influenced by the environment, concrete pore solution, and the passive film formed on the steel surface. The present study used electrochemical methods to successfully characterize the passivation process of steel reinforcements in concrete. The passivation behavior of commonly used HRB400 steel reinforcement material in concrete was studied using various electrochemical parameters quantitatively. As the soaking test time increased, the OCP gradually increased and stabilized after 5 days, indicating that the steel electrode transitioned from an active state to a passive state in the simulated liquid environment of concrete. The steel reinforcement developed a protective passive film that reduced its tendency to corrode. According to EIS, after soaking for one day, the steel electrode showed significant early passivation, indicated by an increase in its arc diameter. The WE arc gradually increased in the first 5 days of immersion, suggesting dynamic passive film formation and development. Beyond 5 days, the passive film stabilized with minimal further changes in its impedance spectrum, indicating carbon steel electrode passivation. The working electrode’s impedance increased significantly on the fifth day, and gradually increased slightly after 10 days, indicating comprehensive coverage by the oxide film. Attributed to the growth and development of the oxide film, the electrode resistance reached a relatively stable state after the fifth day. The shift in corrosion potential offers an indication of the level of passivation of the steel reinforcements. The decrease in the anode Tafel slope and increase in the corrosion potential indicate the formation and stabilization of an oxide film on the steel surface, which is beneficial for its long-term durability in concrete structures. By analyzing the OCP, EIS, and dynamic potential polarization curve method data, it is possible to gain insights into the passivation behavior of steel reinforcements in concrete structures. This study aims to provide a basis for optimizing the corrosion protection of steel reinforcements in concrete structures. The significance of this study lies in a deep understanding of the passivation behavior of steel bars in concrete, providing a theoretical basis for improving the durability and lifespan of steel bars in concrete structures.

9 - Ductility modification technologies

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beamcolumn joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

Corrosion of steel reinforcement in concrete structures is one of the most influencing factors in the loss of durability of reinforced concrete (RC) structures. Neglecting the effects of corrosion has unpleasant consequences and may lead to the failure of structures before their designed life time. Corrosion reduces the cross section of the steel reinforcement, changes the mechanical properties of the steel, decreases the strength of the concrete, and ultimately reduces the capacity and ductility of RC structures. In this study, the effects of corrosion on the moment-curve diagram of structural elements are studied and then compared with the approaches recommended by guidelines such as FEMA-356. To evaluate the effect of steel corrosion on the performance of structures, two RC frames (3-storey and 7-storey) are modeled and two corrosion scenarios are applied to beams and columns of the structures. Then, capacity curves of structures as well as design parameters such as ductility coefficients are obtained by nonlinear static (pushover) analysis of the structures considering the effects of corrosion on moment-curvature diagrams of structural elements. The results show that the coefficient of awareness of 0.75 according to the guidelines such as FEMA-356 can lead to overestimate the structural capacity in highly corrosive environment. It also leads to conservative and uneconomic results in a low corrosive environment. It is observed that the capacities of the 3 and 7-storey structures have been decreased between 19 to 36 percent due to corrosion. Results also show that corrosion reduces the structural capacity between 8 to 28 percent.

The expert interview is devoted to the analysis of the cultural code of Veliky Novgorod and to the architectural techniques, which represent it in the urban environment. The expert considers the general concept of cultural code and examines the modern situation of Veliky Novgorod, where only a small part of authentic objects has been preserved, as most of the structures were destroyed during the Great Patriotic War. Also, the expert evaluates various city objects and projects in terms of combination of Novgorod architectural motifs and modern solutions in them, and emphasizes that the design code, which has been introduced in Veliky Novgorod since 2024, is very poorly connected with the cultural identity of the city. The key thesis of the interview is that all urban objects that are located outside the historic part of the city (outside the berm boundaries) should be resolved in a modern architectural language. In addition, the creation of new projects in contrast with the existing urban environment is described as one of the possible and productive strategies for working in the historical area of the city. In this way, contemporary architects and urban planners can make their original, authorial contribution to the historical city and leave their mark on the urban texture.

Study on collapse of steel-reinforced concrete structure caused by self-weight during construction