"Вестник МГСУ"

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.

The article represents a summarized methodology of the research into small-size pilot metal samples of restored construction facilities. In the article, the co-authors demonstrate an option that provides for the analytical identification of standard characteristic values of mechanical properties, based on initial hardness HRB and conversion of hardness values using the Brinell test. Towards this end, analytical dependence of HB hardness on HRB and HRC is proposed. The numerical identification of the temporary resistance to tensile stress σ
_в required the pre-setting of the value of the average coefficient of relative elongation. This average coefficient was employed to identify the values of relative elongation and contraction, as well as the yield value of the metal. Standard plasticity and strength values were employed to compile an equation for complex criterion C. This criterion was employed to identify the value of relative uniform elongation and transverse contraction, and both were employed to assess the resistance to tensile stress and fatigue. The optical microscopy method was used to identify the pilot sample of the metal as structural carbon steel having grade C15. Its strength analysis based on the properties of its structural components has proven the identity between the sample metal and the aforementioned steel grade. The method proposed by the co-authors helps to identify the metals of restructured construction facilities on the basis of small-size samples to avoid the collapse of metal structures.

This paper considers and asserts the need to obtain the results of inspection of a building at the stage of its commissioning in order to apply comprehensive methodology for assessing its residual life. The author proposes to build regression relationship by correlating the levels of the time series dynamics of stress at certain points of the object calculation scheme considering the results of subsequent surveys. It allows estimating the wear rate of structural elements. The assessment of the reliability and durability of the building frame in a deterministic form is based on the limit states method. The application of this method allows taking into account the random nature of not only the combination of existing loads, but also the strength properties of construction materials by creating a system of safety factors.

The co-authors consider the design solution developed for a panel residence building, type series 1-115, and provide a description of the emergency destruction of structural elements of a 9-storey panel residence building of this type (built in 1979), following a gas explosion. The overall length of the building is 86.4 m; its width is 12 m. The structural system in this building represents a longitudinal wall. Its external longitudinal walls are wade of ceramsite concrete, while its interior walls are made of concrete. Its reinforced concrete hollow slabs rest on the longitudinal load-bearing walls. The transverse walls of staircases are made of concrete blocks. The strip foundation supports the load-bearing walls of the building. The epicenter of the explosion was located in the kitchen on the eighth floor of the building. The kitchen was immediately adjacent to the staircase of the building. Partial destruction of the building followed the gas explosion. Exterior walls of its eighth and ninth floors and the attic were destroyed. Panel buildings designed in pursuance of the longitudinal structural system are more vulnerable to explosive loads compared to buildings designed to the cross-wall structural system, where bearing slabs rest on three interior walls. Thus, all slabs rest on each of the three internal walls of the building on both sides. In the buildings designed to the longitudinal wall structural system, slabs rest on the two walls, one of which is external. The article is based on the report following the inspection of the technical condition of the building, undertaken subsequent to its emergency destruction.

The recent decade has been the time of the rapid development of communication infrastructure, but very often the structures erected in the middle of the last century are used as a basis for new transmission units and antennas, which are considerably worn out. In this regard the control problems of the infrastructure facilities such as towers and masts are often emerging. Such tasks may be associated with the test required when installing additional equipment and modules, as well as during the scheduled inspection and certification of individual objects in accordance with the legal documents. Timely detection of critical deformations will to a large extent prevent the occurrence of accidents and disasters. For accurate detection of deformations load cells on the basis of the piezoelectric effect and fiber-optic sensors based on Bragg gratings are most commonly used, but in such distributed information measurement systems there are significant drawbacks, which narrow the scope of their possible application. Among the main disadvantages there are: high cost of initial installation and configuration, and the subsequent operation of such systems. Traditional measuring sensors require power, separate line of measurement information signal, as well as lines for supplying control signals. A significant limitation is that any sensor detects deformation or other parameters of the design only for its whole base, thus, active sensors should be installed in structures, in which an altered state was detected by visual inspection or by other means. The emergence of video and photo-detectors with high resolution and other settings to get a high-quality image of the object made it possible to establish the systems for infrastructure objects’ monitoring with the characteristics acceptable for practice. At the heart of such systems there are not only detectors with high sensitivity, but also the algorithms for the objects’ recognition, determination of their geometrical parameters by analyzing a series of images. This is the issue and the subject of this work, which developed the computational algorithms to detect external defects. At the stage of preliminary image processing there is the delineation of characteristic points in the image and the calculation of the optical flow in the area of these points. When determining the defect position, the characteristic points of the image are determined using the detector of Harris-Laplace, which are located in the central part of the image. The characteristic points outside the frame are considered to be background. There is an identification of the changes in characteristic points in the frame in relation to the background by using a pyramidal iterative scheme. In the second stage servo frame focuses on a specific point with the greatest change in relation to the background in the current time. The algorithm for object detection and determination of its parameters includes three procedures: detection procedure start; the procedure of the next image processing; stop procedure for determining the parameters of the object. The method described here can be used to create information-measuring system of monitoring based on the use of photodetectors with high-definition and recognition of defects (color differences and differences in the form compared to the background). Since almost each examination of a building or structure begins with a visual examination and determination of the most probable places of occurrence and presence of the defects, the proposed method can be combined with this stage and it will simplify the process of diagnosing, screening for the development of projects on reconstruction and placement of additional equipment on the existing infrastructure.

A study of the climatic conditions of the atmospheric dispersion has been performed within the framework of a hydrometeorological survey of the site of Nizhegorodskaya NPP (Navashino district, Nizhny Novgorod Region).According to the findings of annual synchronous observations performed at the NPP site and at the principal aerological station of Nizhny Novgorod in the median months of seasons, as well as the climatic data analysis over the region, representativeness of data generated at the principal station in relation to the NPP site data has been identified. In particular, it is proven that components of the wind velocity vector at the site and at the principal aerological station differ insignificantly. Analyses of characteristics of the atmospheric dispersion using relevant aerological data covering the period of 47 years (January 1964 to December 2010), as well as analyses of the climatic field of the meteorological dilution factor in the normal mode of operation of a separate power unit have been performed.The author has found that the approach to the study of the atmospheric dispersion is also applicable to the positioning and design of thermal power plants.

Comprehensive Engineering and Radiation Surveys (CERS) constitute the most important component of the final stage of the life cycle of NPPs, that is, decommissioning of nuclear power plants (NPP).Decommissioning of NPPs is accompanied by specific problems, including radioactive contamination, construction of shields, boxes and rooms, and the so-called residual radioactivity. Although these works account for the 20% of the total amount of work associated with decommissioning, they constitute a fundamental difference between decommissioning of any industrial enterprise and an NPP.Objectives, tasks, scopes and other matters of comprehensive engineering and radiological surveys that accompany the decommissioning of nuclear power plants are discussed by the author. They include:information basis, goals and objectives of CERS within the framework of decommissioning of NPP units;CERS programs;methods and means of engineering surveys;findings of engineering surveys;objectives, tasks and scopes of radiation surveys;methods and means of radiation surveys;findings of radiation surveys;objectives, scopes of application and contents of comprehensive engineering and radiation survey reports required for the decommissioning of NPP units;conclusions and recommendations based on the findings provided in CERS in respect of NPP units.

The article covers the relevant problem of dynamic monitoring of buildings and structures. Items exposed to dynamic monitoring primarily include high-rise buildings and structures, as well as buildings and structures exposed to crane loads.The authors provide the general procedure of dynamic monitoring and describe its principal stages. The whole succession of actions that constitute the monitoring of the technical condition of buildings and structures can be split into several stages to be stretched over the time period. The authors demonstrate the technical specifications (including dynamic parameters) of a building or a structure in the process of its operation in the form of a graph. The authors propose their methodology of dynamic monitoring that is considered on the basis of a simple example. The authors argue that the more technically sophisticated the item to be monitored, the tougher the requirements designated for its safe operation; therefore, the interval between the stages of monitoring should be shorter. Unique structures may need monitoring using automated stationary systems to be designed within the framework of special-purpose projects.

The co-authors study the problem of large-scale accidents inside main buildings of steam thermal power plants (TPP), their causes and consequences. Within the framework of the research, the co-authors provide statistical data, frequency of major accidents and their most demonstrative examples. The research demonstrates relationship between large-scale accidents and equipment layouts inside main buildings. The model developed by the co-authors may be used to assess the reliability of individual engineering systems (power units), and their interconnection.As a result, the main building is represented as a set of independent engineering systems having similar or different degrees of reliability calculated or defined empirically. Some types of accidents within these systems may cause large-scale accidents, as well as accidents within other systems that maintain no immediate connection to the system already exposed to the accident, but remain in the same building. It is proven that efficient improvement of reliability of any engineering systems depends on the threshold of economic viability. The best solution consists in reduction of the number of engineering systems arranged within one main building.

Some results of high-rise buildings monitoring program are presented in this paper. The monitoring system is currently operating at the high-rise apartment building in Moscow. The vibrating wire strain gauges were embedded in the foundation slab and groundlevel walls during the construction. Measurements are carried out automatically at 6-hour intervals, and received in real time by the monitoring station. In this paper the result of measuring the strain in the concrete walls during 4 years is reported.The computer model of the building was made in order to compare the experimental and predicted data. Mathematical models of a high-rise building are simplified, but we are taking into account the main factors, that influence the stress-strain state of reinforced concrete structures. These factors are: influence of soil base, phases of construction and change of concrete deformation characteristics. The total strain in constructions was calculated as a sum of a strain under load, thermal strain, plastic shrinkage and creep. This data was compared with the total strain in structures measured by the gauges.The analysis of quantitative and qualitative correspondence between the model and actual data was performed. The comparison shows that the theoretical results obtained by the performed procedure are similar to the experimental data. It demonstrates that the model reflects the actual behavior of constructions. The differences found during the comparison are due to the redistribution of stresses from one part of a construction to the other that can occur even if the load is constant. This phenomenon is clearly seen during the suspension of construction. Some differences due to unaccounted factors were found, which should be investigated later.

The article reveals comparative results of experimental model studies of the dynamical characteristics of containment shells used for their calculation and construction as well as actual calculation of dynamic characteristics and the results of actual full-scale investigations executed after 40 years of their operation. This comparison of present-day calculations and full-scale researches showed their agreement with the previous investigations performed on physical models of containment shells.The dynamic analysis of the facilities on the base of physical models were widely used in the 70's of the 20th century, when the computers were still in the initial level of development. The results of these model studies were used to justify the strength of critical structures, including nuclear power plants (NPPs), some of which have already worked for over 40 years. The current investigation gives the opportunity to compare the results of the previous model studies with the present calculations of NPP protective containments (shells) and the field studies results. The field investigations were carried out on the reactor containment of VVER-1000 reactor for the 1st unit of Kalinin NPP.1. Model studies of the dynamic characteristics on the physical model base. In order to provide dynamic model studies in the laboratory it is necessary to solve the following problems: 1) to fulfill certain similarity conditions, which provide unambiguous recalculation of the results to the full-scale structures; 2) to determine the scale of the model and its production material, which is related to the structure and characteristics of the vibration-testing machine (shaker), the transitional fixing devices for the model, special vibrators for dynamic loads, etc. The particular attention should be paid to the registration, processing and analysis of dynamic parameters, taking into account quality changes, which have recently occurred in the measurement technique. The model studies were carried out on a series of geometrically similar models of the protective containments fabricated under special technology of gypsum (1:100 scale) and plexiglas (1:200 scale). The models were mounted on a specially designed shaker. Harmonic oscillations with continuous frequency scanning were set up to the testers and resonant vibration frequency was recorded. Then the shell vibration mode was defined at these frequencies using small-sized mobile vibrometer. The frequencies of natural oscillations were recounted for correlation on similarity conditions.2. The study (investigation) of the dynamic characteristics of the protective containment on the base of mathematical model. The model is built in ANSYS calculation software complex and is structurally similar to the physical model, but without built elements and elastic foundation (i.e, the adopted conditions are similar to the physical model). The problem is solved in three-dimensional setting, all elements are made of three-dimensional elements (of solid type). The comparison of the experiment results on physical models and field studies is given in the Table.

The article describes the results of a comprehensive survey of the bridge structure in Dubna. The survey was performed to determine the load capacity and maintainability of the bridge structures for the period prior to the repair, as well as to collect the information necessary to update the draft decision and the right strategy of major repairs. The growing needs of the city Dubna, which several times increased the operational loading of the bridge structures, and no major repairs since the construction, led to the need of restricting the traffic capacity of the only transportation artery. By the time of the survey in November 2011, contraflow over the bridge and the restricted traffic of more than 8 t was organized, which resulted in tense atmosphere in the city.The authors studied the historical data and design features of the supporting structures of the bridge. Particular attention was paid to the state of load-bearing structures of the bridge and their deformability. The strength characteristics were studied. The authors analyzed the results of calculations in order to determine the carrying capacity of the bridge structures with the test loads. It turned out that the carrying capacity of the bridge is sufficient for load accommodation. However, in accordance with the regulations, the bridge does not meet modern requirements for the travel width. It was recommended to maintain contraflow and to provide operational loads of the class H-10 (i.e. platoons with GVW of 10 t and the presence of a single vehicle in a platoon with GVW of 13 t) until the major repairs. After major repairs with restoration of bearings, waterproofing, water disposal system, replacing the bed, repair of the protective layer, it will be possible for single vehicles weighing up to 25 t to pass over the bridge.

This paper demonstrates how temperature measurements of the water filtered by earthfill dams can be used to determine the soil filtration ratio and to monitor the condition of earthfill dams.
The ground water temperature change is caused by the processes of heat conductivity and convection. The analysis of heat transfer within earthfill dams demonstrates that the speed of thermal waves varies between (4-6) 10-7 m/s. Therefore, whenever the water filtration ratio is under 4 ∙10-7 m/s, propagation of thermal waves is driven by the heat conductivity. If the soil filtration ratio is below 2∙10-5 m/s, thermal waves are caused by forced convection (the filtration flow).
Temperature measurements of the water filtered by earthfill dams composed of non-cohesive soils make it possible to calculate averaged soil filtration ratios with an error under 20-40 %. This result is more precise than the one generated through the application of other natural methods (pumping out, use of indicators, etc.).
Temperature measurements of the water filtered by earthfill dams composed of cohesive soils make it possible to control their density and water penetration capacity, and to identify their thermal conductivity.
This paper demonstrates that the relocation of a thermal wave within non-cohesive soils prevents the filtration flow from remaining in a steady-state condition. As a result, complex secondary water flows are generated within the filtration flow by means of natural convection (the temperature gradient). Secondary water flows in question represent the principal cause of well-known abnormalities of depression curves of earthfill dams.

The following conclusions were made upon completion of the testing of crane beams:
The lowest rigidity is demonstrated by welded beams exposed to temporary mobile loads; the maximal buckling caused by temporary mobile loads is equal to 12 mm, or 1/1,1790 of the span; the rigidity of crane beams of an overflow dam meets the requirements set by Section E2.1 of Construction Rules 20.13330.2011 "Loads and Actions".
In general, the authors state that the crane beams of the span structure of the overflow dam are in a serviceable operating condition, according to their opinion issued upon completion of examination and testing procedures. The recommendation is to regularly tighten screw nuts and to install high-strength bolts in the points of missing rivets. The authors also recommend applying a rust-proofing coating to all metal structures of the dam spans.

The most typical types of crane substructures destruction are wear of crane rails, details of its fixation, deformation of crane beams, settlement or tilting of the columns. At technical examination of buildings and structures with crane rails their planned-high-altitude position is determined. There exist a list of methods for determining the crane rails’ planned-high-altitude position, each of them has its disadvantage, expressed in the final result - the real position of crane rails. While estimating their position from the ground, i.e. mounting transit on the ground, and indicating devices above, there is an inaccuracy on the rails, which is caused by different moments of indications fixation, both on the plan and hightwise. The authors carried out observations of the position of craneways both on the plan and heightwise for determining the reason of craneways bearing structures’ deformations and the period of their influence of railtrack state. The results of these observations are analyzed and presented. The authors present their suggestions on advancing the crane operation, which will increase its operation life.

The article discusses possible defects of exterior walls of buildings that can occur in a multilayer brick masonry. The article is based on the inspection materials of the school building located in Bronnitsy, Moscow Region. The reasons of brick masonry defects are considered and analyzed. An external wall strength calculation of the stairwell of the building is given, confirming the reasons for the formation of defects in the masonry. The static calculation results of the exterior wall of the building stairwell revealed the presence of tensile forces in the zone of window sill of the lower window opening of the exterior wall of the building. The calculations of masonry tensile showed that load bearing capacity of the masonry in window sill zone is not provided. Thus, the calculation is justified for cracks in the window sill area of the calculated wall. The appearance of hairline cracks on the outer face of a decorative protective layer multi-layer masonry is due to the thermal deformations, the manifestation of which is enhanced by the presence of the layer of effective insulation located behind the layer of masonry and embarrassing action of rigid ties on the development of thermal deformations.

The authors describe the methodology and results of dynamic field testing of the building of a universal pool under construction, as well as its eigenfrequencies, identified through the employment of a computer model.
The subject of the research represents the building of a universal pool under construction in Anapa. The general goal of this research is to identify the seismic stability of the building structure. An unbalance-type vibration machine was used in the course of the testing procedure. The machine was designed and manufactured at Moscow State University of Civil Engineering.
Identification of natural vibrations of building structures and verification of the identity of the computer model and the natural behaviour of the structure were to be completed to assess the required modes of operation of the vibration machine. Identification of full-scale dynamic characteristics was performed through the employment of the impulse method of vibration excitation.
Comparative analysis of experimental vibration frequencies and eigenfrequencies identified in the course of calculations based on different mathematical models demonstrates their similarity in terms of local shapes of vibrations, namely, in terms of buckling vibrations of an "annular" beam employed for the purpose of measurements taken in the course of the testing procedure. Frequency values identified in the course of testing and calculations vary from 4.5 to 19.8 Hz.
Calibration of the vibration machine represents another objective of the experiment. The experiment has demonstrated that the whole operating range of frequencies (2 to 15Hz) is to be employed in the course of testing procedures described above.

This article covers the problems of theoretical assessment of the seismic stability of a 16-storied building made of precast concrete box units by full-scale experimental testing through the employment of a powerful unbalance-type vibration machine. The authors provide the results of the experimental testing and scale them to assess the effects of an earthquake.
The testing procedure that consists in the assessment of the seismic stability of buildings through employment of the vibration testing performed by a powerful vibration machine installed on the soil surface, have proven its high efficiency.
As a result of the vibration testing, specific values of accelerations and shifts in terms of the building height and length were identified in lateral and longitudinal directions.
The results of extrapolation of the seismic effect of the vibration testing onto the 9-grade seismic load scale have proven that the buildings of this type can be considered seismically stable.

An important element of modern automated systems of management, monitoring and control of remote access modules is information about the state and behavior of a static or moving object. In many existing and planned monitoring systems processing graphical image of the object is used, which is obtained by the photo detectors and, thus, the possibility of determining geometric and kinematic parameters of a moving object is significantly reduced due to various aspects of image acquisition, one of such aspects is blur. In the present work, algorithms of the primary information processing obtained on the basis of the graphic image study of a movable or stationary object are improved using the methods and procedures of statistical analysis that allow approximating theoretical results to experimental results. The use of statistical analysis and probabilistic approach increase the accuracy of the determined characteristics, applicability of calculation procedures of the state parameters (size, shape, distance from the observer) and behavior of the object (speed and direction) and reduce the computational complexity of the final algorithm. The Bayesian estimation was obtained based on the use of quadratic, rectangular and simple loss function under normal, Laplace, uniform and lognormal distribution of errors, which allow drawing conclusions about the intervals of various models and algorithms to determine the parameters of different objects. When using the statistical approach it is taken into account that the errors are random in nature and may be considered a variety of probability density functions (normal, lognormal, Laplace and uniform distributions to minimize risks under different loss functions (quadratic, rectangular, linear), and then evaluated using the method of least squares, method of least modules and the Bayesian approach. When performing the evaluation the properties of unbiased, consistency and efficiency are important. Sustainable procedure should have the following properties: for the selected model, the procedure should be close to optimum efficiency; the results should be close to nominal, calculated for the adopted model; the effect of large errors must be eliminated. We use the minimax method of Huber, which assumes that the best estimate will not be worse than in the case of the “least favorable” density distribution. Decision rule is based on the definition of such density that minimizes the information of Fischer that is the variance function of the contribution of the sample. In the present study we offer the procedure of finding a theoretical function based on the assumption that the errors are subjected to the known laws of distribution: normal (Gaussian), Laplacian, uniform, lognormal. This is a significant advantage of the proposed methodology compared to the one used in the previous works of the authors, it is proposed here to use the Bayesian estimation of the measurements as unknown theoretical function that needs to be obtained closer to the observational measurements.

Various defects, which occur because of the influence of different environmental factors become the reason for the emergencies of building structures. Monitoring of certain parameters of bearing structures in the process of their erection and beginning of operation will help detecting negative processes which may endanger mechanical safety of buildings. The authors offer the operating results of automated monitoring system of the bearing structures state of the ice arena “Shayba” in the Olympic park in Sochi during the earthquake which happened on December 23th, 2012. The arena was equipped with a dynamic monitoring system, which helped estimating the influence of a seismic occurrence on the building constructions, to make prompt conclusions on absence of damages of the bearing structures, get important data on the dynamic response of the structure.