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Many buildings during their operational period incur damage of different origin: man-made, natural, operational, etc. Dynamic tests are performed for detailed assessment of the technical condition of buildings and structures in accordance with the regulatory documents for general analysis of the building damage state. In a large number of papers, the results of comparison of full-scale tests and numerical analysis using finite element method are presented. When analyzing the results, it can be concluded that the dynamic method is reliable, but has several limitations. The advantage of the dynamic method of building damage assessment is the possibility to adjust finite element models in software systems taking into account results obtained from in-situ tests, which allows to obtain more accurate results for the assessment of bearing capacity under seismic loading. To examine the effect of damage to buildings on their seismic resistance, an experiment with corrosiondamaged reinforced concrete columns was performed. The result of the first stage of the experiment is the assessment of the change in dynamic characteristics (eigenfrequency, vibration decrement, vibration damping coefficient, etc.) of reinforced concrete column specimens subjected to corrosion damage.

The article describes features of operation and monitoring of low-water bridges, which are found on highways of regional, intermunicipal and local importance. Vibrations of the bridge span are considered in detail, taking into account its interaction with other structural elements and the environment. As a characteristic, the change of which takes into account the change in the state of the bridge structure, it is proposed to use the frequency of natural vibrations. To simulate the dynamic effects of transport and the dynamic behavior of individual elements and the entire structure as a whole, it is proposed to use viscoelastic elements of the Kelvin–Voigt type. When solving the problem, an approach has been implemented that makes it possible to take into account the anisotropic properties of the superstructure associated with various reinforcement along and across the roadway of the bridge, and to present the design scheme of the span not in the form of a beam supported at the edges with the help of hinges or viscoelastic dampers, but in the form of a plate, which can have different fxing conditions along the entire contour. The use of the proposed model and approach will make it possible to obtain the necessary data on the state of low-water bridges, for which there is often no possibility of visual inspection or instrumental inspection from the lower side of the bearing part of the superstructure. By the values of the frequency of natural vibrations, it is possible to estimate the water level above the low-water period and predict food situations, during which the roadway of the low-water bridge may be fooded.

In this work using a finite element study the author has numerically solved the problem of the dynamic behavior of a multifunctional coating of an aircraft protective element. The researcher conducted the simulation using the Femap with NX Nastran software package, The result of the modal analysis is the values and patterns of natural and secondary vibration modes of the multifunctional coating of the protective element of the aircraft using a special module the author has determined the distribution of effective modal masses in tabular form, Also, as a result of calculations, the author of the article obtained the value of the structural rigidity of the protective coating, The results presented in this work allow us to analyze the behavior of protective systems and structural elements of an aircraft with a multifunctional coating applied to the outer surface in real operating conditions, The design team can use the research results of this article in order to increase the efficiency of the development of a new structures and structures of a composite coating for multifunctional purposes, protective elements and materials for space technology

Introduction. Add-on compactors for excavators (ACE hereinafter) are replaceable working equipment for excavators. They are used for soil compaction after the backfill of trenches, wells, foundation cavities and other “narrow spaces” of construction, as well as soil compaction at slopes of embankments and excavations.In practical use of ACE, builders face two challenges:to justify the choice of an ACE for soil compaction under given conditions determined by the soil type and moisture, layer thickness, and the required compaction factor; to determine the time required to compact soil with an ACE at a single point positional compaction to ensure the required compaction factor of a given type of soil in a layer of required thickness.The problems above require the information regarding technological capabilities of ACEs in different technological situations of soil compaction. The assessment of such technological capabilities of ACEs, at the same time, should take into account the ongoing transition to a new regulatory framework in Russia in the field of assessment indicators for the results of soil compaction in construction.Materials and methods. ACE technological capabilities review was conducted based on the information provided on the official websites of the largest Russian and foreign ACE manufacturers and suppliers.Conclusion. The analysis of information provided by ACE manufacturers and suppliers showed that most of that information is technical specifications of ACEs and excavators. There is almost no information on technological capabilities of ACEs. At the same time, ACE manufacturers and suppliers use ambiguous terminology (for example, “compaction volume”) in the assessment of technological capabilities.Practical value. Lack of information on technological capabilities of ACEs in various technological situations of soil compaction leads to errors in selection of an ACE model and its operation time during single point positional soil compaction, which increases the risk of under compaction and reduced service life of constructed objects. To solve this problem, the Construction and Road-Building Machinery Department of Yaroslavl State Technical University is developing a methodology for calculating the results of soil compaction with an ACE in different technological situations.

Two problems of the monoharmonic sound wave transmission through a thin rectangular composite plate hinged in the opening of an absolutely stiff dividing wall were considered using the discrete layered damping model of a multilayer plate at small displacements and deformations, with account of the internal damping of layers according to the Kelvin–Voight model. In setting the first problem, it was assumed that the plate located between two semiinfinite spaces and a plane sound wave with a given amplitude value of the pressure is incident on it. In setting the second problem, it was considered that the plate is situated between two absolutely stiff barriers; one of them, owing to the harmonic vibration with a given displacement amplitude of the plate, forms an incident sound wave, while the other is stationary and coated by an energy-absorbing material with high damping properties. Behavior of the acoustic media was described by the classical wave equations based on the model of an ideal compressible fluid. Exact analytical solutions of the formulated problems were constructed. With their help, the sound insulation parameter of composite plate reinforced with carbon fiber textile was studied and the characteristics of its stress-strain state were investigated depending on the frequency of the incident sound wave. It was shown that the mechanics of the deformation of structural elements made of fiber-reinforced composites under high-frequency acoustic impact must be described by refined equations of motion, which have a high degree of accuracy and pithiness, because the stress-strain state formed in them are almost three-dimensional.

One of the main means of reducing aerodynamic noise is the use of silencers, which can be made of various porous materials, depending on the specific operating conditions. The aim of the work is to study the dependence of the noise reduction on the characteristics of porous permeable materials (PPM) obtained by vibration molding from metal powders. Such PPMs have a wide range of porosity, high permeability, mechanical strength, provide the ability to work in a wide temperature range, high corrosion resistance, and therefore find more and more widespread application in practice. When designing silencers, their pore size, permeability, mechanical strength, cost, and the chemical composition of the material are taken into account. Basic research methods – determination of noise level, powder particle size, permeability coefficient, pore size. Vibration molding of PPM samples for experimental studies was carried out on a ВЭДС 10-1А vibration bench with vibration parameters that ensured the maximum bulk density of the powder in the mold (acceleration 10 m/s2, frequency 500 Hz). Main results – the dependence of the noise reduction value on the PPM characteristics obtained by the method of vibration molding of metal powders of various grades of various particle size distribution was studied. It has been shown that the most effective damping is provided by PPM from spherical bronze powder of the БрОФ10-1 grade with particle sizes of 350–400 microns, which provides at the same time a combination of a high level of noise reduction and high permeability to air or gas. It was found that the thickness of the muff significantly affects the efficiency of noise suppression, while the minimum thickness of the muff, which provides a sufficiently high degree of noise reduction, is about 3.5 mm, therefore it is not practical to increase the thickness of the muffler material above this value.

Introduction. Currently, manufacturers of vibrating plate compactors practically do not give recommendations on the choice of model and justification of the equipment operating modes when compacting the soil in specific process conditions. This is partially due to the lack of a methodology for determining the results of soil compaction with vibrating plate compactors. One of the development stages of such technique should be the analysis of the technical characteristics of vibrating plate compactors, which could reflect experience in the production and operation of the equipment. Materials and methods. The authors conduct statistical processing of technical characteristics of vibrating plate compactors in STATISTICA 10 based on 65 models of various manufacturers from Russia and other countries.Discussion and conclusions. The authors demonstrate that the operating modes of vibrating plate compactors are between the operating modes of vibrating rollers and self-propelled vibrating plate compactors. To note, relative driving forces are in a similar range as the working range of self-propelled vibrating plate compactors, and their vibration frequencies are in a similar range as the working range of vibrating rollers. Moreover, low values of the determination coefficient for oscillation frequency and relative forcing force depending on the mass of the equipment also indicate the lack of consensus among manufacturers about the required characteristics of vibrating plate compactors and an assessment of their technological capabilities.Due to a significant excess of driving force of vibrating plate compactors over their weight, the base of the plate should come into partial uplift from soil, and that should be taken into account while the mathematical model of interaction development between vibrating plate compactors and soil. Practical implications. The results of the analysis reveal the peculiarities of the vibrating plate conductors’ interaction with the compacted soil and also clarify the requirements for the future mathematical model. The resulting regression dependencies of driving force and oscillation frequency, as well as the base dimensions of the vibrating plate compactors, the weight of the excavator and the required oil consumption should be taken into account when developing a methodology for determining the results of soil compaction with mounted technological excavator plates. Therefore, the obtained results could also be used by manufacturers in the design and modernization of the vibrating plate compactors’ structures.