ISSN / EISSN : 1997-0935 / 2304-6600
Current Publisher: Moscow State University of Civil Engineering (10.22227)
Total articles ≅ 1,879
Latest articles in this journal
Vestnik MGSU, Volume 16, pp 128-143; doi:10.22227/1997-0935.2021.2.128-143
Introduction. Experimental methods for studying vibrations of buildings and structures (dynamic tests) make it possible to determine an individual set of parameters of dynamic characteristics of natural vibrations inherent in each building and structure. The method of standing waves was chosen to determine dynamic characteristics; it allows to obtain detailed (with the required degree of detail) and, most importantly, reliable data on the technical condition of the building. Materials and methods. Mobile diagnostic unit “Standing Wave Method” (MSW) recorded the micro-seismic vibrations of building constructions. The layout of sensors with a single reference point was chosen. The standing wave method was applied to develop the software package in order to process the micro-seismic vibrations of the building. Vibration coherence spectra were analyzed to identify the natural frequencies of the building. A GIS model was developed to demonstrate the amplitudes and phases of vibrations in the building. Results. Eigenfrequencies, peak amplitudes, and phase characteristics of the building’s wave field were determined. Patterns of distribution of amplitudes and maps of vibration phases were constructed. Areas, accommodating destructive processes in the brickwork of the building’s bearing walls, were identified and the reasons for their occurrence were established. Conclusions. The dynamic characteristics of the building were obtained in reliance upon the results of dynamic tests of the office building. The analysis of the distribution of these parameters allowed to assess the technical condition of the building and to make recommendations towards its strengthening. The author suggests that the mobile diagnostic system, employing the standing wave method, can be used to resolve a wide range of problems.
Vestnik MGSU, Volume 16, pp 144-152; doi:10.22227/1997-0935.2021.2.144-152
Introduction. Angle shear studs, attachable by powder-actuated fasteners, are used as an alternative to traditional welded elements ensuring the shear connection of steel-reinforced concrete slabs. The objective is to revise their strength characteristics for different options of steel-reinforced concrete slab designs pursuant to SP 266.1325800.2016. Materials and methods. The programme of laboratory tests was developed in compliance with GOST R 58336-2018 to identify the strength behaviour of angle shear studs. Static shear testing of angle studs was performed at the LISMIiK laboratory of the Moscow State University of Civil Engineering using universal servo-hydraulic reconfigurable testing machine MTS.Multiaxial.DS1.4811.DS1.50019, designated for the testing of static and dynamic loads applied to large constructions. Displacements were measured by a tripod-mounted piston-type indicator. Results. The programme of theoretical and experimental research into the behaviour of a shear connection with angle shear studs in steel-reinforced concrete slabs that also had steel deck profile sheets was developed on the basis of the analysis of regulatory documents and sources of research information. Laboratory tests showed that the strength of the shear connection in an angle stud depends not only on the geometry of the steel deck, used as the stay-in-place formwork, but also on the position of a shear stud in the deck. Conclusions. The results of the theoretical and experimental research can be used to obtain new information about the strength and deformability of angle shear studs, connected by powder-actuated fasteners with the help of high strength expansion anchors; they allow to revise the currently used provisions governing the calculation of the reduction factor pursuant to SP 266.1325800.2016 with account taken of the design parameters of a shear connection.
Vestnik MGSU, Volume 16, pp 153-167; doi:10.22227/1997-0935.2021.2.153-167
Introduction. The development of probabilistic approaches to the assessment of mechanical safety of bearing structural elements is one of the most relevant areas of research in the construction industry. In this research, probabilistic methods are developed to perform the reliability analysis of steel truss elements using the p-box (probability box) approach. This approach ensures a more conservative (interval-based) reliability assessment made within the framework of attaining practical objectives of the reliability analysis of planar trusses and their elements. The truss is analyzed as a provisional sequential mechanical system (in the language of the theory of reliability) consisting of elements that represent reliability values for each individual bar and truss node in terms of all criteria of limit states. Materials and methods. The co-authors suggest using p-blocks consisting of two boundary distribution functions designated for modeling random variables in the mathematical models of limit states performed within the framework of the truss reliability analysis instead of independent true functions of the probability distribution of random variables. Boundary distribution functions produce a probability distribution domain in which a true distribution function of a random variable is located. However this function is unknown in advance due to the aleatory and epistemic uncertainty. The choice of a p-block for modeling a random variable will depend on the type and amount of statistical information about the random variable. Results. The probabilistic snow load model and the numerical simulation of tests of steel samples of truss rods are employed to show that p-box models are optimal for modeling random variables to solve numerous practical problems of the probabilistic assessment of reliability of structural elements. The proposed p-box snow load model is based on the Gumbel distribution. The mathematical model used to perform the reliability analysis of planar steel truss elements is proposed. The co-authors provide calculation formulas to assess the reliability of a truss element for different types of p-blocks used to describe random variables depending on the amount of statistical data available. Conclusions. The application of statistically unsubstantiated hypotheses for choosing the probability distribution law or assessing the parameters of the probability distribution of a random variable leads to erroneous assessments of the reliability of structural elements, including trusses. P-boxes ensure a more careful reliability assessment of a structural element, but at the same time this assessment is less informative, as it is presented in the form of an interval. A more accurate reliability interval requires interval-based assessments of distribution parameters or types of p-boxes applied to mathematical models of the limit state, which entails an increase in the economic and labor costs of the statistical data.
Vestnik MGSU, Volume 16, pp 186-201; doi:10.22227/1997-0935.2021.2.186-201
Introduction. The article addresses the problem of irrational treatment of solid municipal, production and consumption waste in Russia, as well as the prospects of using secondary raw materials in the construction of buildings. The research is focused on environmental standards, environmental certification systems in the construction industry, as well as recycled materials. The study encompasses the construction of buildings using recycled materials, taking into account the requirements set in environmental standards. Materials and methods. The article presents several types of secondary raw materials and an overview of sustainable approaches to the construction of buildings using recycled materials in Russia and abroad. Most widely spread construction technologies, used to build houses using secondary raw materials, are described. An environmentally friendly facility constructed in Russia using secondary raw materials is described as an illustration. Results. The state of the Russian legislative framework governing the treatment of solid municipal, construction, and consumption waste and the requirements of international and Russian environmental standards applicable to buildings are analyzed. The percent ratio of waste management actions is determined in relation to other requirements set by environmental certification systems applicable to real estate items. Conclusions. A new classification of construction products made of secondary raw materials is presented. Conclusions are made about the feasibility of reusing solid household, industrial and consumption waste in the construction industry. The need to revise environmental standards in Russia is identified. The Russian environmental standards should have a larger number of criteria determining the rational treatment of solid municipal, construction, and consumption waste as well as the use of products made of secondary raw materials.
Vestnik MGSU, Volume 16, pp 168-175; doi:10.22227/1997-0935.2021.2.168-175
Introduction. The majority of construction sites feature complex geotechnical conditions, as they have alternating soil layers, including loose soils. A pile foundation is the principal type of foundations constructed on these sites. This article encompasses a problem statement and a solution to the problem of interaction between a long pile and multilayer underlying soils. Materials and methods. The problem is explored in linear and nonlinear settings. The S.P. Timoshenko elastoplastic model is analyzed to describe nonlinear shear deformations. Analytical and numerical methods are employed to present the solution. The results of the analytical solution are compared with the results of the elastic problem obtained using the Plaxis 3D software package. Results. An equation designated for determining the reduced shear modulus of the multilayer soil mass is obtained. Analytical solutions are supported by the graphical solution obtained using Mathcad software. Numerical solutions are obtained using the Plaxis 3D software package. The diagrams describing the dependence of the settlement of the pile, that passes through alternating soil layers, on the load are provided. The diagrams, describing the dependence between the force, applied to the pile toe, and the pile radius in case of a variable load applied to the pile head and variable pile length are provided. Conclusions. The resulting dependence, needed to determine the reduced shear modulus of the multi-layer soil mass, demonstrates good convergence with numerical methods in the elastic setting. These solutions can be used to pre-determine the displacement of a long pile surrounded with the underlying multi-layer soil mass. The selection of an optimal correlation between the pile length and the pile diameter allows for the most effective use of the bearing capacity of the pile.
Vestnik MGSU, Volume 16, pp 176-185; doi:10.22227/1997-0935.2021.2.176-185
Introduction. Water resistance is one of durability criteria of building materials. As a rule, the value of the liquefaction ratio is applied to assess the water resistance. However, even water resistant materials are not always able to withstand cyclical weather impacts that cause linear deformations, reduced strength and cause destruction of building products. Therefore, it is necessary to take into account the resistance of building materials, namely, their resistance to alternating humidification and drying (airproof performance). The purpose of this research is to study the producibility of molded composites containing a modified magnesium binder that features higher resistance to weather impacts. Materials and methods. The magnesium binder was modified by the silica fume and high pressure molding to increase the water resistance and airproof performance of the composites. The influence produced by the modifier on the change in the compressive strength of dried and water-saturated molded composites, liquefaction and airproof performance ratios, as well as linear deformations of the reference specimens were studied following a pre-set number of cycles of alternating wetting and drying. Results. The water resistance and airproof performance of construction products, containing magnesia binders, may be improved by the micro-silica, added to pressed mixtures, and their compaction by press molding. Compositions of molded composites, containing a modified magnesia binder, were developed for the manufacture of products used to make enclosing structures and for the flooring of rooms having the indoor humidity of over 60 %. Conclusions. It is established that molded composites containing a modified magnesia binder feature high resistance to alternating wetting and drying. The proposed method of modifying magnesia binders prevents the destruction of molded stone-like materials containing these binders in case of exposure to alternating stresses; it reduces linear deformations and, as a result, decelerates the fatigue failure. The use of a recyclable material as a mineral additive must contribute to the reduction of the cost of products and allow to consider the method of their production as one of the best technologies available.
Vestnik MGSU, Volume 16, pp 202-219; doi:10.22227/1997-0935.2021.2.202-219
Introduction. Several types of embankment dams are used in the hydraulic engineering practice. However, the choice of a dam is individual for each hydraulic engineering project, as it takes account of specific features and natural conditions. This paper compares two types of rockfill dams (the one having a concrete face and the other having an asphalt-concrete diaphragm) in relation to the Mullalakh HPP on the Pskem River in the Republic of Uzbekistan. The dam height is 85 m. The comparison was performed from the standpoint of the dam performance in case of exposure to static forces and high seismicity. Materials and methods. The analysis of (1) the stress-strain state (SSS), (2) the stability of slopes exposed to regular and irregular load combinations was conducted for two types of dams. All calculations were performed in the two-dimensional domain. The analysis of the stress-strain state took account of the non-linear behavior of the soil ground and the contact interaction between structural elements. Seismic loads, included into the scope of irregular loads, were identified using the response spectrum method applied to particular periods and self-oscillation modes. Slope stability was analyzed with regard for the stress state of soils identified in the course of SSS calculations. Results. Each type of embankment dams has its specific features. The asphalt diaphragm dam is worse at perceiving high seismic loads. Its SSS during an earthquake features strength loss and emergence of soil discontinuity zones. The disadvantage of a concrete face dam is the insufficient safety of its anti-seepage element. Supplementary measures are needed to ensure the appropriate stress state of the face. Another finding is that the slopes of both types of dam do not demonstrate a sufficient stability factor, if the slope ratio equals to 1.5 during a 9-point earthquake. Conclusions. In high seismicity regions, a concrete faced dam demonstrates better performance than the asphalt diaphragm dam if both are exposed to static and seismic forces.
Vestnik MGSU, Volume 16, pp 220-241; doi:10.22227/1997-0935.2021.2.220-241
Introduction. Reduction of project cost overruns is a key objective of Russian production facilities against the background of tightening domestic and international market competition, a spike in the number of projects implemented within the framework of the investment programme, including large strategic investment projects, scarcity and high costs of sources of financing. The mission of this research is to offer an approach to the development of a system of key risk indicators of an construction project that will allow the management team to make decisions ahead of the occurrence of risk-bearing events to reduce cost overruns and to stay within the pre-set budget values in terms of capital costs of a project. Materials and methods. The co-authors have analyzed currently used approaches, instruments and methods, applicable to the development of the system of key project indicators, and classified project risks using the Ishikawa diagram. Their approach encompasses instruments and methods of the risk theory (identification and assessment of risks and key project indicators), as well as instruments of the regression correlation analysis. Results. The co-authors present an algorithm for the development of a system of key risk indicators and an approach to the listing of key project indicators broken down by project significance criteria. Conclusions. The application of the proposed approach to highly significant projects will ensure a detailed project-specific listing of key project indicators applicable to monitor the project implementation. A standard set of instruments and methods, requiring minimal human resources and time, can be applied to other projects. Besides the new approach, the co-authors offer a description of a list of potential key project indicators that enable to forecast changes in capital costs, broken down by risk factors.
Vestnik MGSU, Volume 16, pp 12-19; doi:10.22227/1997-0935.2021.1.12-19
Introduction. The article presents the results of the analysis of changes in the planning structure of an urbanized area, addresses land use for crude oil recovery purposes in the Basra governorate, and explores the influence, produced by this activity on urban development and the environment using the city of Basra as an example. Crude oil recovery reduces the size of natural areas. The practical aspect of the scientific research entails the development of an information system designated for land management and the maintenance of databases focused on the study of urban planning tasks to ensure well-balanced development of areas, rich for crude oil in the Basra governorate with regard for a structured regional planning pattern as one of the most important objectives of Iraq. Growing residential areas, on the one hand, and expanding areas occupied by oil recovery and industrial enterprises, on the other hand, have been a relevant post-war problem since 2003. The environmental disorder, caused by substantial changes in land use, involves various disruptions, which translate into grave problems of the urban environment experienced by the governorate of Basra. Materials and methods. Official data, submitted by the Basra administration, tables, documents and cartographic materials were used to perform this research, let alone the open source information, including maps that contain statistical calculations made using the ArcGIS10.x software package and Microsoft Excel. The co-authors also performed a retrospective analysis of the Basra territory using remote sensing, which allowed them to determine the boundaries of the city and to track its spatial transformation. Results. The retrospective analysis has identified changes in the city borders. High economic growth, boosted by oil production and developing industrial territories, drives the need for well-balanced territories focused on sustainable development, especially in the historical part of Basra which is suffering from degradation. Conclusions. The problem of unbalanced use of urbanized territories and environmental sustainability of cities, affected by wars and military operations, requires the development of regulations governing the delimitation of borders within the framework of a land-use plan to be developed.
Vestnik MGSU, Volume 16, pp 75-90; doi:10.22227/1997-0935.2021.1.75-90
Introduction. Pipeline systems are exposed to several conditions that lead to a drastic reduction in their durability, primarily due to variable low-frequency and high-frequency loads arising in a process pipeline due to the operation of compressor units. Hence, fatigue failure occurs, leading to the pipeline failure. As early as at the pipeline installation stage, sections of process pipelines have weld connections, and thermal welding cycles have an adverse effect on the properties of materials exposed to fatigue loading. The study of weld connections in steel pipelines exposed to high-frequency vibrations and effects of weld seam defects on durability characteristics are the focus of this research. Materials and methods. Low-carbon pipeline steel St20 was selected for the study. The radiographic inspection method, optical metallography, microhardness of structural phases, and the method of high-frequency fatigue tests were used. Results. The results and principal conclusions about the effect of welding defects on durability characteristics of welded samples, made of pipeline steel and exposed to high-frequency fatigue tests, are presented; structural changes in weld connections are analyzed using optical metallography and microhardness methods. Defects of weld seams and their dimensions were identified by means of radiographic inspection. A comparative analysis of durability limits, demonstrated by the parent metal of the model material that has defective weld connections, and the same limits of defect-free samples is provided. The main causes of failure of weld joints, exposed to high-frequency vibrations, are identified. Conclusions. Having summarized the research findings, we can argue that high-frequency vibrations have a negative impact on the parent metal of a process pipeline and its weld joints. The weld seam is the point of failure; defects trigger destruction, and their presence has a higher impact on fatigue characteristics than their dimensions or types. Characteristics of durability in case of exposure to high frequency loading applied to a weld joint in the gigacycle range are 67 percent below those of the parent metal.