"Вестник МГСУ"

In the article, the authors perform the assessment of the reliability of overlappings of a warehouse building owned by Vysokovol'tnyy Kabel' Open Joint Stock Company. The assessment is performed in 25-38/А-D axes on the basis of the bearing capacity criterion. The authors have assessed the compliance of the condition of the restructured building with the regulatory requirements issued by the Federal Service in charge of Ecological, Technological and Nuclear Supervision, Federal Law № 116-FZ On Industrial Safety of Hazardous Industrial Facilities, issued on July 21, 1997, and Federal Law № 384-FZ Technical Regulations of Safety of Buildings and Structures, issued on December 30, 2009, in terms of the assurance of safe maintenance of the above industrial building.
The warehouse building is located within the area occupied by the Moscow cable factory. It occupies a two-aisle section of a single-storied industrial building in 25-38/А-D axes. The climatic area represents Area II, the subsection of the climatic zone is 2B. The warehouse has a metal frame; it is made of I-shaped steel columns and beams that have reinforced concrete floor slabs resting on them. The foundations are made of reinforced concrete posts resting on the concrete foundation mat.
As a result of a specialized analysis, the authors have identified that the probability of compliance of the steel beams with the requirements of the first group of limit states, with account for the identified damages, is equal to 5σ. The analysis of the structure of the overlapping and the columns demonstrates that their bearing capacity and rigidity are sufficient to resist the principal combinations of load, including the loads that come from the two allied loaded loaders of Doosan series (48B AC) that represent a short term load.

Subject: studying the main directions for increasing durability and safety of unique, technically complex objects on the example of the Kayrakkum HPP. The peculiarity of operation of this kind of structures is the specificity of physical, chemical and mechanical factors that negatively affect their durability. However, complexity of the technical solution execution does not allow us to completely replace these structures after expiration of their standard service life. Taking into account the uniqueness of the HPP, the programs for the operational suitability restoration are individual. The main problems of reconstruction are considered, which consist in the necessity of, firstly, increasing the station’s productivity, and secondly, ensuring the stability of the dam to erosion and scours. Research objectives: the goal of the study was to develop proposals for improvement of operational suitability of the Kayrakkum HPP based on data on the technical condition of its main units, buildings, and rockfill dam. Materials and methods: in the process of long-term operation, due to filtration processes, seismic influences, the performance parameters of buildings and structures of hydropower plants deteriorate, which negatively affects the reliability of their operation. Therefore, based on the methods of mathematical statistics, data on the projected flood were analyzed. The data on the technical condition of the main HPP equipment were also analyzed and the main directions of its modernization were determined. Results: an assessment of the probability of destruction of the dam showed the need to strengthen it to reduce water filtration. A comparative analysis of possible options for reconstruction of the Kayrakkum HPP has shown the need for an integrated approach that will allow us to solve both the issues of ensuring safety requirements in accordance with international quality standards and enhancement of the plant’s capacity to increase the generation of electricity, the demand for which has increased over time. Out of four technological solutions to reduce filtration into the body of the dam, an option of the central diaphragm from the secant bored piles has been chosen as the least affecting the production cycle of the entire complex. Conclusions: the results of this work can be used when clarifying the repair work organization project to link the technological cycles in such a way as to reduce the losses in generation of electricity caused by execution of works on reconstruction.

The authors argue that bearing walls of buildings that have up to four stories can be designed and made of small cellular concrete blocks. These walls demonstrate advantages specific to solid masonry walls. For example, they have high water vapor permeability. Whenever the internal humidity increases, half of the moisture content can be extracted from the masonry due to the water vapour permeability of external walls, while the other half of the moisture content can go back into the room (due to the sorption capacity of the wall material). Furthermore, any lower density wall material has smaller heat absorption capacity to ensure a comfortable environment.The application of small cellular concrete blocks as a wall material is an alternative to thoroughly insulated multi-layer external walls. The authors present options of structural solutions of external walls of buildings.It is noteworthy that due to the relatively low strength of cellular concrete, walls have a low bearing capacity. Cellular concretes are brittle.Control tests of small cellular concrete blocks made in the natural environment do not always prove the desired compressive strength. In addition, strength properties of small cellular concrete wall blocks may vary. The authors present their findings in terms of their examination of the technical condition of mid-rise buildings that have walls made of small cellular concrete blocks. The authors consider the reasons for the defects of walls made of small cellular concrete blocks.

Upon examination of eleven main buildings of power plants, analysis of defects and damages of building structures was performed. Thereafter, the damageability of principal bearing structures of main buildings of thermal plants was analyzed. It was identified that the fastest growing defects and damages were concentrated in the structures of operating sites. The research of the rate of development of the most frequent damages and defects made it possible to conclude that internal corrosion of the reinforcing steel was the most dangerous defect, as far as the reinforced concrete elements of operating sites were concerned. Methods of mathematical statistics were applied to identify the reinforcing steel development pattern inside reinforced concrete elements of floors of operating sites. It was identified that the probability of corrosion of reinforced concrete elements of operating sites was distributed in accordance with the demonstrative law. Based on these data, calculation of strength of reinforced concrete slabs and metal beams was performed in terms of their regular sections, given the natural loads and the realistic condition of structures. As a result, dependence between the bearing capacity reserve ratio and the corrosion development pattern was identified for reinforced concrete slabs and metal beams of operating sites. In order to analyze the sufficiency of the bearing capacity of building structures of operating sites in relation to their time in commission, equations were derived to identify the nature of dependence between the sufficiency of the bearing capacity of reinforced concrete slabs and metal beams of the operating sites and their time in commission.

On an example of a complex engineering structure with aerodynamically unfavorable constructive form, equipped with mechanisms dampers, the results of long-term observations of the oscillation frequency under the influence of wind loads were reviewed. The experimental dependence of the first tone oscillation frequency on time for this structure is shown. The hypothesis on the causes of frequency oscillations change in engineering structures in time is proposed. The experimental data confirms this hypothesis. The results of a comparison of the experimental data for long-term observations with the oscillation frequency in accordance with the safety criteria of GOST 31937-2011 “Buildings and Constructions. Rules of inspection and monitoring of the technical condition” are shown. It has been shown that the results of comparison indicate technical safety of the whole object. It is offered to use dynamic monitoring systems for technically complex heavy-duty engineering structures for early detection of the transition beginning of the control object to the limited functional or emergency condition.

Introduction. The subject of the study is the study of technologies to ensure the reliability of sewage pumping stations (SPS), exploited in the Far North. One of the most important problems is the freezing of water in the SPS tanks, associated with the incorrect selection of the insulation of the SPS of new TPPs, as well as the deterioration of the insulation of the SPS under the influence of aggressive media on the old TPPs. As a solution, the article considers two main methods of internal heating: liquid and electric. Both methods were analyzed using the example of the Yakutsk State District Power Plant-2, where the disruption of the drainage system may lead to a station shutdown. Materials and methods. The purpose of the study was a comparative analysis and selection on the basis of a feasibility study of the most reliable method of heating the pumping unit of the Yakutsk State District Power Plant-2, exposed to low temperatures and, as a consequence, the freezing of wastewater in tanks. On the basis of field surveys and the processing of their results using mathematical statistics, the causes of the problem of water freezing in the SPS units at Yakutsk State District Power Plant-2 were studied and analyzed. Technological characteristics of the installed SPS were also analyzed, heat engineering calculations were performed, economic indicators were calculated, and further solutions to the problem under consideration were determined. Results. Analysis of the technical parameters and configuration of the SPS showed that the installed insulation and the heating system do not correspond to the territorial conditions in which this equipment is installed. To bring the SPS into working condition, two solutions for internal heating of tanks were developed and their comparative analysis was performed. Selected heating option with heating cable. This system has been successfully implemented and is operating normally. Conclusions. The results of the work can be used to repair thermal insulation and install a heating system for industrial pumping stations without using earthworks in the conditions of the Far North and on the territory of permafrost soils.