Mechanical safety of reinforced concrete structures at all stages of the life cycle

Ensuring the mechanical safety of operated buildings at all stages of the life cycle is an urgent task. This is especially important when planning major repairs and reconstruction in buildings, as well as determining the period of safe operation from the moment of the survey, i.e. clarification of the remaining service life. The total service life at the design stage is set by the customer and the general designer in accordance with the recommendations of GOST 27751-2014 «Reliability for constructions and foundations. General principles». Mechanical safety and durability are ensured when calculating structures using the limit state method, assigning protection measures depending on the operating conditions, as well as complying with the requirements of SP 255.1325800.2016 «Buildings and structures. Operating rules. General Provisions». A method for preliminary assessment of the mechanical safety of buildings and their structures is proposed for consideration, which eliminates some of the shortcomings of existing methods for calculating the residual life by physical wear (damage) of building structures based on the results of a visual inspection, the basis of which is the dependence of the allowable safe operation period on the percentage of reduced bearing capacity. It is proposed to use the results of a visual inspection performed in accordance with GOST 31937-2011 «Buildings and constructions. Rules of inspection and monitoring of the technical condition»

Development of the Method for Calculation of Reinforced Concrete Structures on the Formation and Opening of Normal Cracks

This paper presents the history of the development of the method for calculating the crack resistance of reinforced concrete elements according to Soviet and modern design standards, which was based on the work of the Soviet and foreign scientists, such as: A.F. Loleit, V.I. Murashev, A.A. Gvozdev, S.A. Dmitriev, A. Clark, J. Monier and others. Also, the article discusses the currently updated calculation methods for the formation and opening of normal cracks according to domestic and foreign standards

V.G. Shukhov Radio Tower – history, current state and prospects

The Moscow Radio Tower was erected in 1922 and is an object of cultural heritage of the Russian Federation, a monument of architecture and engineering. The tower consists of six sections, each about 25 m high. The frame of the sections is a hyperboloid structure, the principle of which was developed by V.G. Shukhov at the end of the XIX century and is still used worldwide in the design and construction of tower structures. The technical inspections carried out confirmed the emergency condition of the Moscow Radio Tower. The results of laboratory studies have shown the heterogeneity of the strength and chemical characteristics of steel, its non-weldability and cold breakage. Analysis of the development of defects over time revealed that the condition of the tower is deteriorating. The performed emergency measures exclude a sudden collapse, but do not eliminate the emergency condition of metal structures. Taking into account the need for urgent restoration work with the elimination of the emergency condition of the tower, the development of project documentation began in 2023. The design assignment provides for the maximum possible preservation of the original elements. When carrying out the project, it should be taken into account that it is impossible to remove individual elements without completely unloading the entire structure. All elements of the tower that have mechanical or corrosion damage that reduces the cross-section even in certain sections are not repairable and must be replaced with new ones. When reusing existing elements, it will be technically difficult to carry out the reverse assembly with the necessary accuracy

Standardization of requirements to operation of buildings and facilities

Safe operation, reliability and durability of capital facilities (hereinafter – CF) are becoming more and more topical. All phases except operation (including all types of maintenance and repairs) and demolition were covered by regulatory requirements, while operation as the longest phase in CF life and the final stage - demolition were not included into regulations until recently. There were industry specific codes for nonproduction and industrial buildings and facilities and documents derived from them, but they were inconsistent, lead time to repair differed even for similar structures and operation conditions and these discrepancies did not allow setting the specific frequency of repairs which resulted in neglected defects and damages shortening the life of buildings and structures or causing accidents. In 2015, the authors, in team with other experts, developed SP 255.1325800.2016 “Buildings and structures. Rules of operation. Key provisions” (hereinafter - SP 255), setting general requirements to operation of buildings and structures under regular conditions, but the diversity of buildings’ functions required the development of numerous codes of practice derived from SP 255 and some of them were drafted in 2016-2018. Codes of operation practice will (if elaborated) contribute to the reduction of operation and maintenance costs and ensure required safety of capital facilities

Evaluation of the impact of compliance of precast discs of overlapping on the work of the frame of a multi-storey building

The article provides an analysis and justification of the need to take into account the compliance of discs of overlapping and coatings when calculating frames from precast concrete structures. Previously conducted full-scale experiments showed that the rigidity of the precast overlapping with full filling of the seams, in comparison with the monolithic overlapping, decreases by 3-15 times due to the ductility of the joints. The use of refined computational models of structural solutions for frames, which take into account the compliance of the conjugations of elements, makes it possible to trace possible redistribution of efforts. Such an approach when reconstructing, it is possible to optimally select and calculate the enforcement of structure, and on new designing, to increase reliability and / or improve the economic performance of frame buildings. According to the results of analytical studies, formulas were adopted for the parameters that allow one to take into account the overall compliance of overlapping disks and coatings in computational models of building frames. Numerical studies on the computational model of a frame building made it possible to evaluate the effect of accounting for compliance on the stress-strain state of a multi-storey frame

Structural features of buildings from metal structures

The article is devoted to the issue of preserving the architectural heritage of the outstanding Russian engineer V.G. Shukhov. Three objects are considered: the Moscow Radio Tower on Shabolovka, the “Shukhov Prolet” of the Sheet Rolling Shop and the Water Tower, located in the city of Vyksa, Nizhny Novgorod Region. The main design parameters of these structures and the results of their technical examination, the emergency response measures taken to ensure the safety of the Radio Tower in Moscow, and recommendations for the restoration of all three structures with the transfer of the Sheet Rolling Shop and the Water Tower to the central part of Vyksa are presented. It is planned to reconstruct the historical appearance of the buildings, as well as to improve the surrounding area. It is supposed to restore the geometric shape of the section by laser deposition of powder metal, and only if it is impossible to restore the element, its replacement is provided. To preserve the historical appearance, the joints of steel structures will be bolted, imitating rivets. In the course of excavation, archaeological research is planned, since within the boundaries of the construction site (the city of Vyksa) there may be areas of preserved cultural strata of the cultural heritage site “Estate-industrial complex, XVIII-XIX centuries”

Modular frame trusses of buildings

The paper describes space-planning and structural concept in source-efficient buildings that provides multiple functions of the rooms and large-span space.The main load-bearing structures of two adjacent storeys are metal trusses with parallel chords between which (between top and bottom chords) intermediate storeys are designed and the space between trusses is occupied by the free plan storeys. Bottom and top chords of the truss resist together with floor structure forming two-storey steel-reinforced concrete unit. To calculate value of deformation capacity for nodal connection a numerical experiment focused on modelling a part of building from solid finite elements has been performed. The results of performed analysis are the average values of stiffness of nodal interface of solid floor slab on corrugated deck and truss chords for finite elements KE 55 of typical layout (of flat finite elements). The obtained average values of stiffness were introduced into structural design of flat finite elements. Taking into account flexibility of floor slab that supported by middle trusses for the given structural concept leads to decreased span bending moments and increased support bending moments by 25% compared with hinge support of floor

Mechanical safety of reinforced concrete structures at all stages of the life cycle

Ensuring the mechanical safety of operated buildings at all stages of the life cycle is an urgent task. This is especially important when planning major repairs and reconstruction in buildings, as well as determining the period of safe operation from the moment of the survey, i.e. clarification of the remaining service life. The total service life at the design stage is set by the customer and the general designer in accordance with the recommendations of GOST 27751-2014 «Reliability for constructions and foundations. General principles». Mechanical safety and durability are ensured when calculating structures using the limit state method, assigning protection measures depending on the operating conditions, as well as complying with the requirements of SP 255.1325800.2016 «Buildings and structures. Operating rules. General Provisions». A method for preliminary assessment of the mechanical safety of buildings and their structures is proposed for consideration, which eliminates some of the shortcomings of existing methods for calculating the residual life by physical wear (damage) of building structures based on the results of a visual inspection, the basis of which is the dependence of the allowable safe operation period on the percentage of reduced bearing capacity. It is proposed to use the results of a visual inspection performed in accordance with GOST 31937-2011 «Buildings and constructions. Rules of inspection and monitoring of the technical condition»

V.G. Shukhov Radio Tower – history, current state and prospects

The Moscow Radio Tower was erected in 1922 and is an object of cultural heritage of the Russian Federation, a monument of architecture and engineering. The tower consists of six sections, each about 25 m high. The frame of the sections is a hyperboloid structure, the principle of which was developed by V.G. Shukhov at the end of the XIX century and is still used worldwide in the design and construction of tower structures. The technical inspections carried out confirmed the emergency condition of the Moscow Radio Tower. The results of laboratory studies have shown the heterogeneity of the strength and chemical characteristics of steel, its non-weldability and cold breakage. Analysis of the development of defects over time revealed that the condition of the tower is deteriorating. The performed emergency measures exclude a sudden collapse, but do not eliminate the emergency condition of metal structures. Taking into account the need for urgent restoration work with the elimination of the emergency condition of the tower, the development of project documentation began in 2023. The design assignment provides for the maximum possible preservation of the original elements. When carrying out the project, it should be taken into account that it is impossible to remove individual elements without completely unloading the entire structure. All elements of the tower that have mechanical or corrosion damage that reduces the cross-section even in certain sections are not repairable and must be replaced with new ones. When reusing existing elements, it will be technically difficult to carry out the reverse assembly with the necessary accuracy