75504 2712-8172 4 96 2020 1-156

RAR RUS 3-14 Kazan State University of Architecture and Engineering Salakhutdinov Marat lider-kazann@yandex.ru

Kazan, Russia

Kazan State University of Architecture and Engineering Gimranov LinurLinur leenur@mail.ru

Kazan, Russia

Kazan State University of Architecture and Engineering Kuznetsov Ivan kuz377@mail.ru

Kazan, Russia

Joint-stock company "Special economic zone "Innopolis" Fakhrutdinov Adel faxrutdinoff@yandex.ru

Innopolis, Russia

LLC "Tatneft-Presscomposite" Nurgaleeva Lilia nurgaleevalm@fiberpull.ru

Elabuga, Russia

PFRP structures under the predominately short term load The subject of the study is a load bearing capacity of building structures from fiber reinforced polymer (FRP) shapes under the short term load, such as snow load and occupancy load, which significantly exceed values of dead load. Experimentally determined actual strength and stiffness under the short term load of following structural members and connections: of I-beams; bolted connections under the bearing load with different directions of material’s pultrusion relatively to applied force; connections transferring load via contact surfaces, at the ends of structural members, oriented normally to the direction of pultrusion; webs of the I-beams under locally applied load perpendicularly to the direction of pultrusion. Experimental studies deemed following results. Minimal flexural strength of beams obtained experimentally is on average 1.25 times higher than values of flexural strength determined theoretically. Strength of different types of connections obtained after testing procedures is on average 1.35–2.5 times higher of its theoretical values. Conducted studies allow widening of the field of an applicability of FRP profiles as structural members of small scale structures subjected to predominantly atmospheric or live loads, for instance, tiered and covered seating pavilion. Such types of structures subjected to short term load allow to utilize strength and stiffness of their structural members more deeply. 10.18720/MCE.96.1 pultruded FRP profiles bolted joints experimental studies https://engstroy.spbstu.ru/article/2020.96.1/

RAR RUS 15-20 14063693600 https://orcid.org/0000-0001-9659-8091 Seismological Division of Geophysical Survey of Russian Academy of Sciences Liseikin Aleksei lexik1979@mail.ru

Novosibirsk, Russia

https://orcid.org/0000-0003-2366-550X Seismological Division of Geophysical Survey of Russian Academy of Sciences Seleznev Victor svs0428@mail.ru

Novosibirsk, Russia

https://orcid.org/0000-0002-9061-4537 Dagestan Division of Geophysical Survey of Russian Academy of Sciences Adilov Zarahman adilov79@mail.ru

Makhachkala, Russia

Monitoring of the natural frequencies of Chirkey arch dam The article presents a method for monitoring the natural frequencies of HPP dams according to continuous seismic observations. The object of the research is the largest arched dam in Russia, the Chirkey HPP located in the Caucasus. If damaged, it could cause great loss of property and human life, but disasters can be minimized by using effective dam structural health monitoring. The study for changes in the natural frequencies of engineering structures is one of the most common methods of remote control over their structural health. However, the determination of values of natural frequencies of huge concrete dams is a very difficult procedure due to their have complex construction. Moreover, interpretation of changes in the natural frequencies values is difficult due to the significant influence of the water level in the reservoir.  Consequently, at the initial stage, we performed a detailed study of the natural oscillations of the dam using the method of coherent restoration of the standing wave fields with the definition of both the natural frequencies of the structure and their modes. They were conducted twice at the minimum and maximum upstream level and for the first time highlighted the features of seasonal changes in the full field of standing waves. The normal modes were determined that are present in oscillations at different upstream levels and which frequencies can be detected continuously from the records of seismic equipment. The series of frequency changes during the year are calculated. For the first time we established that, frequency changes are by 5 to 11 days behind reservoir level changes and assumed that relaxation processes of the dam body and / or its base cause the delay after the upstream level changes. We calculated dependencies for predicting the frequency values from the reservoir level, taking into account the delay time. As a result, we proposed an approach for monitoring of the dam structural health based on a comparison of the observed natural frequencies with the predicted ones. The developed method can be applied to monitor the structural health of concrete dams of other HPPs. 10.18720/MCE.96.2 arch dam structural health monitoring natural frequencies normal modes standing waves https://engstroy.spbstu.ru/article/2020.96.2/

RAR RUS 27-41 57194104035 0000-0002-6640-103X National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” Bilous Inna biloys_inna@ukr.net

Kyiv. Ukraine

6506189670 0000-0002-8218-3933 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” Deshko Valeriy te@kpi.ua

Kyiv, Ukraine

57140834000 0000-0002-5895-1306 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” Sukhodub Irina ira_krot@ukr.net

Kyiv, Ukraine

Building energy modeling using hourly infiltration rate In Eastern Europe countries, including Ukraine, a significant part of the buildings belongs to the mass development of the 80s, which are characterized by a low level of energy efficiency. For such countries with sharply continental climates, heating costs prevail to a large extent. Improved thermal protection forces more attention to be paid to heat losses with ventilation. The distribution of air exchange between individual rooms is difficult to determine, especially due to natural ventilation. The work is devoted to considering the conditions of natural convection and determining the effect on the energy consumption of a building. The article considers the advanced ASHRAE technique for calculating natural air exchange. The influence of the temperature and wind characteristics of the outdoor air on the natural component of the air exchange rate at the different locations of the representative rooms of an 8-story building is analyzed. The value of the air exchange rate for typical conditions of Kiev does not exceed 0.25 h-1, 0.65 h-1 and 0.4 h-1 for two-chamber and single-chamber double-glazed windows, triple glazing in wooden double binders, respectively. On the first floors, air exchange is associated with air infiltration, and on the last floors there is exfiltration, which must be taken into account when dynamically modeling the energy characteristics of a building. The example is with additional mechanical ventilation to maintain a comfortable environment. 5R1C dynamic grid models were created to study the energy performance of the building. The estimate of additional heating costs due to infiltration is 23 % for the North and 43 % for the South orientation of rooms with two-chamber energy-saving windows. It has been established that in dynamics, the energy consumption of a building with normative air exchange and the calculated value of the natural component differs by 50–75 %, which is a possible level of savings under actual air exchange conditions in comparison with standard ones. This savings can be reduced by increasing air exchange during busy hours, for example, due to additional aeration. 10.18720/MCE.96.3 buildings energy efficiency ventilation air exchange rate temperature heating https://engstroy.spbstu.ru/article/2020.96.3/

RAR RUS 42-59 Russian Scientific Research Institute of Land Improvement Problems Kosichenko Yuri kosichenko-11@mail.ru Russian Scientific Research Institute of Land Improvement Problems Baev Oleg Oleg-Baev1@yandex.ru Efficiency and durability of the linings channels of geosynthetics The investigation is concerned with seepage-control canal lining made of geosynthetic materials (GSM): polymer geomembranes and bentonitic mats (bentomats) with protective coatings. Efficiency and longevity criteria of lining made of geomembranes, bentomats and protective coatings (concrete, stone, gabi-on, and soil) have been stated. New lining designs with GSM of high reliability are proposed, including two or three layers of seepage-control lining made of bentomats and geomembranes, as well as protective layers made of geotextiles, rock filling, gabions. We have considered the effectiveness of already constructed sections of Bentofix bentomat linings at Donskoy principal canal (Rostov region, Russia) according to the following three criteria: -     Filtration costs of the bentomat lining compared to the ground bed, -     Efficiency degree due to the bentomat lining compared to the alternative options, -     Filtering resistances of the bentomat lining compared to the alternative options. We have developed a technique to assess the effectiveness of bentonite mats taking into account the regeneration (self-healing) of possible damage due to the regeneration of Ca-bentonite. It is based on the method of successive change of steady states, when the nonsteady process of filtering through damages of the bentomat is divided into a number of steady states. Studies of the aging coefficient of the geomembrane made of polyethylene (HDPE) by the modulus of elongation in the test basin during the period of 8–10 years have made it possible to extrapolate these data and determine the longevity (service life). There is also a calculation of the geomembrane longevity according to the Arrhenius equation. We have made a comparative analysis of the efficiency of various types of canal linings which showed that the most effective type is the bentomat liner, which also has the highest service life. 10.18720/MCE.96.4 anti-filter liner geocomposite material polymer geomembrane geocomposite material geosynthetic clay liner filtration https://engstroy.spbstu.ru/article/2020.96.4/

RAR RUS 60-69 Wasit University Ayoob Nadheer natheers227@uowasit.edu.iq

Wasit-Kut, Iraq

56548386400 https://orcid.org/0000-0002-4023-7382 Wasit University Abid Sallal sallal@uowasit.edu.iq

Wasit-Kut, Iraq

Wasit University Hilo Ali dralinasser@uowasit.edu.iq

Wasit-Kut, Iraq

Wasit University Daek Yasir yasirhd327@uowasit.edu.iq

Wasit-Kut, Iraq

Water-impact abrasion of self-compacting concrete Abrasion erosion is one of the serious problems that encounters the concrete surfaces exposed to speedy water flow in hydraulic structures, affects their service life and poses the need to expensive maintenance works. Some parts of the hydraulic structure like chute blocks and baffle piers in spillways are designed to face direct impact of water and waterborne materials. For such type of loading, the water-jet test method can be used to simulate the abrasion erosion of concrete surfaces. In this study, an experimental work was conducted to evaluate the abrasion erosion of self-compacting concrete under the effect of water impact. Plate specimens from six mixtures with 30, 40 and 50 MPa design stengths and with 0, 0.5, 0.75 and 1.0 % steel fiber contents were tested using the water-jet method. The results showed that increasing the strength from 30 to 40 MPa can reduce the abrasion losses by approximately 17 %, while using steel fibers with volumetric contents of 0.75 and 1.0 % can improve the abrasion resistance by more than 23 %. It was also concluded that the best percentage abrasion resistance improvement was gained when the strength of the plain specimens was increased to 50 MPa, which was 30 % compared to the plain 30 MPa sample. 10.18720/MCE.96.5 abrasion self-compacting concrete steel fiber fiber-reinforced concrete impact https://engstroy.spbstu.ru/article/2020.96.5/

UNK RUS 70-78 57191529586 https://orcid.org/0000-0001-7083-7963 Vologda State University Solovyov Sergey ser6sol@yandex.ru

Vologda, Russia

A probabilistic approach to estimation of the ultimate load of end-bearing piles on settlement criterion Pile foundation is one of the most common types of foundations in the presence of soft soils. The safety of the entire structure depends on the pile foundation safety. Stochastic (probabilistic) modeling of load-bearing elements is a modern trend in the quantitative structural safety assessment. The article describes the probabilistic approach to estimate the bearing capacity (ultimate load) of end-bearing piles on settlement criterion. Design load and elastic modulus of a pile material are the main stochastic (random) parameters that determine the probability of end-bearing pile failure. The graphical model of failure and safety areas is proposed, on the basis of which conclusions can be drawn about the allowable load during the design and inspection of pile foundations. The numerical example shows that the method of pile reliability analysis based on FOSM (First Order Second Moment) gives similar results as the method on the basis on FORM (First Order Reliability Method). Therefore, for an accurate evaluation of the reliability index (according to the considered mathematical model), the first iteration of the FORM method is sufficient. Experimental modeling of pile behavior showed good convergence of the theoretical result with the experimental result based on the Monte Carlo method. For a comprehensive reliability analysis of end-bearing piles, it is necessary to consider a pile as a system (in terms of reliability theory). 10.18720/MCE.96.6 pile end-bearing pile settlement FORM bearing capacity reliability index https://engstroy.spbstu.ru/article/2020.96.6/

RAR RUS 79-93 6504446571 0000-0001-6981-7420 Jordan University of Science and Technology Al-Rousan Rajai rzalrousan@just.edu.jo

Irbid, Jordan

0000-0001-9272-920X Jordan University of Science and Technology Abo-Msamh Isra’a iabomsamh@gmail.com

Irbid, Jordan

Impact of anchored CFRP on the torsional and bending behaviour of RC beams The scientific problem considered in the study is indeed one of the problems in the modern theory of reinforced concrete. Despite a significant number of studies on the problem of bending with torsion, to date. There are no sufficiently reliable solutions to this problem that most fully reflect the physical nature of the problem. In the last two decades, using of Carbon Fiber Reinforced Polymers (CFRP) in strengthening of deficient reinforced concrete structural elements has been increased due to their ease of installation, low invasiveness, high corrosion resistance, and high strength to weight ratio. Strengthening damage structures is a relatively new technique. Therefore, the intent was to appear at the essential CFRP external strengthening technique that provides an efficient increase in the shear and flexural strengths as maintaining ductile failure mode. However, anchoring and debonding problems remains a challenge for the accomplishment of this technique. In this study, a novel application was implemented in which the CFRP sheet was integrated as external shear strengthening for RC beams. Therefore, this study investigated the behavior of simply supported RC beams strengthened externally with anchored CFRP composite using and subjected to combined bending and torsion using Nonlinear Finite Element Analysis (NLFEA). Seventeen models have been constructed and divided into four groups to scrutinize the effect of CFRP anchored depth and CFRP strip spacing. The performance of each beam was evaluated in terms of failure mode, CFRP strain, load-deflection and torsion-twist behavior, ultimate deflection, ultimate load capacity, ultimate angle of twist, ultimate torsion capacity, elastic stiffness, and energy absorption. The enhancement percentage increased with the increase of anchored depth and decreased with the increase of CFRP strip spacing. Finally, the external strengthening with anchored had a superior effect on the ultimate load, ultimate deflection, angle of twist, torsion elastic stiffness, energy absorption. 10.18720/MCE.96.7 reinforced concrete structural strength structural models bonding torsion flexural strength fiber reinforced polymer https://engstroy.spbstu.ru/article/2020.96.7/

RAR RUS 94-109 57196066346 0000-0002-8051-5914 National Research Moscow State Civil Engineering University Denisov Aleksandr den-al-v@inbox.ru

Moscow, Russia

Radiation changes of concrete aggregates under the influence of gamma radiation The work (in connection with the small study of the effects of gamma ray on concretes and their components) contains the results of calculation and analysis of radiation changes of concrete aggregates under the influence of gamma ray on the basis of analytical methods developed previously during the neutron irradiation process. The possibility of using these analytical methods in the case of exposure to gamma ray was substantiated. The relationship of the absorbed doses of gamma ray of different energies with the number of atoms displaced during irradiation was established. There is an assessment of radiation changes in the volume and strength of the main types of rocks - aggregates of concrete (igneous, sedimentary rocks and ores) under the influence of gamma ray with an average energy of 2 MeV and 5 MeV after irradiation to absorbed doses of 105 to 1011 Gy at 30 °C, 100 °C and 300 °C. For this, from the beginning, the radiation changes of the main rock-forming minerals were calculated, and on the ground of them, the radiation changes of rocks of concrete aggregates were calculated. It has been established that noticeable radiation changes of considered minerals and rock aggregates will occur only at absorbed doses of gamma ray of more than 1ꞏ109–1ꞏ1010 Gy of gamma rays with an energy of 5 MeV and of 3ꞏ109–3ꞏ1010 Gy for gamma rays with an energy of 2 MeV. The number of radiation changes grows with a rise in the absorbed dose and significantly decrease with an increase in the irradiation temperature for silicate class minerals and silicate rocks. The greatest radiation changes under the influence of gamma ray at 30 °C are observed in silicate minerals and rocks, especially olivine pyroxenes, hornblende, dunite, peridotite, pyroxenite, and gabbro. Moreover, even with an absorbed dose of gamma ray of 1011 Gy, the radiation changes are not large (increase in volume is not more than 0.36 %, decrease in strength is not more than 8.7 %). As the temperature increases, the ratio in the magnitude of radiation changes of different materials changes. 10.18720/MCE.96.8 aggregates of concretes radiation changes in volume and strength influence of gamma radiation https://engstroy.spbstu.ru/article/2020.96.8/

RAR RUS 110-117 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University "Moscow Power Engineering Institute" Kirsanov Mikhail mpei2004@yandex.ru

14, Krasnokazarmennaya, 111250 Moscow, Russia

Analytical dependence of the deflection of the spatial truss on the number of panels A statically definable girder truss consists of two flat side trusses with parallel belts and descending braces, connected along the upper and lower belt by horizontal ties. The truss at the corners has four supports, the vertical reaction of one of which is selected from the equilibrium condition of the structure as a whole. Several types of external load are considered: the load in the middle of the span, vertical, evenly distributed over the nodes of the upper or lower belt, and uniform horizontal (wind), applied to the nodes of the upper belt. The forces in the rods and supports are determined by the method of cutting out the nodes. The deflection is found by the Maxwell-Mohr formula under the assumption of linear elasticity of the rods. The dependence of the deflection on the number of panels is obtained from solving problems for trusses with a consistently increasing number of panels. Generalization of these solutions to an arbitrary number of panels is found using special operators of the Maple computer mathematics system. Using the Maple operators, we derive and solve homogeneous linear recurrent equations that satisfy the coefficients of the desired formula. The found dependence has the form of a polynomial in the number of panels. Curves of the deflection dependence on the number of panels, the load and the size of the structure are constructed.  Some asymptotic properties of the obtained solution are found. Formulas for the dependence of forces in the most stretched and compressed rods on the size of the structure, the load, and the number of panels that can be used to analyze the strength and stability of the structure are derived. 10.18720/MCE.96.9 spatial truss exact solution induction deflection wind load asymptotics Maple https://engstroy.spbstu.ru/article/2020.96.9/

RAR RUS 118-128 S-1676-2017 6507460407 0000-0002-8907-7869 Tashkent Institute of Irrigation and Agricultural Mechanization Engineers Mirsaidov Mirziyod theormir@mail.ru

39, Kori Niyoziy St., Tashkent, Uzbekistan, 100000

57209308835 https://orcid.org/0000-0002-0432-2758 Tashkent Institute of Irrigation and Agricultural Mechanization Engineers Khudainazarov Sherzod scherzodshox77@mail.ru

Tashkent, Uzbekistan

Spatial natural vibrations of viscoelastic axisymmetric structures A mathematical model, methods and algorithm to assess the spatial natural vibrations of axisymmetric structures are given in the paper taking into account the variability of the slope and structure thickness in the framework of the viscoelastic theory of shells. Dissipative properties of the material are taken into account by the Boltzmann-Volterra hereditary theory of viscoelasticity. The spatial natural vibrations of high-rise ventilation pipes of the Armenian nuclear power plant (NPP) and smokestacks of the Novo-Angren, Syrdarya, Azerbaijan and Ekibastuz thermal power plants (TPP) were studied taking into account the elastic and viscoelastic properties of their material. The reliability of results was verified by comparing the results obtained with the exact solution of a number of test problems, as well as by comparing the results with the results of field experiments. It was found that when the viscoelastic properties of structure material are taken into account, the decrement of their vibrations weakly depends on the values of eigenfrequency. Along with this, the dangerous range of earthquake frequencies includes not only the bending frequencies of the structure, but the spatial ones as well. 10.18720/MCE.96.10 axisymmetric structures high-rise smokestacks spatial vibrations eigenfrequency vibration decrement dynamic characteristics viscoelasticity dissipative properties https://engstroy.spbstu.ru/article/2020.96.10/

RAR RUS 129-137 M-6585-2013 6508103761 0000-0002-1196-8004 Peter the Great Saint Petersburg Polytechnic University Vatin Nikolai vatin@mail.ru

Polytechnicheskay, 29

56352359500 0000-0002-5156-7352 Volgograd State Technical University Sergey Korniyenko svkorn2009@yandex.ru

28, Lenina Ave., Volgograd, Russia, 400005

15730895100 http://orcid.org/0000-0003-3251-3356 Saint Petersburg State University of Industrial Technologies and Design Gorshkov Alexander alsgor@yandex.ru

St. Petersburg, Russia

Peter the Great Saint Petersburg Polytechnic University Pestryakov Igor iscvisota@mail.ru

Polytechnicheskay, 29

Peter the Great St. Petersburg Polytechnic University Olshevskiy Vyacheslav 79119199526@yandex.ru

29 Politechnicheskaya St., St. Petersburg, 195251, Russia

Actual thermophysical characteristics of autoclaved aerated concrete The characteristics of autoclaved aerated concrete blocks was tested and analyzed in comparing with Standards’ requirements. The results of the study show that the actual thermophysical characteristics of autoclaved aerated concrete blocks, cut from product samples of the three largest manufacturers, in most cases do not coincide with the values declared by the manufacturers and presented in the standards prepared with their direct participation. The mismatch between the calculated and actual values of the thermal conductivity of materials and products used in the installation of external walling, leads to an increase in transmission heat losses through the external walls and the waste of thermal energy for heating and ventilation of buildings. In this regard, a radical review of the values declared by manufacturers, as well as the standards on the basis of which the products are manufactured, and their correct presentation in the current regulatory documents are required. 10.18720/MCE.96.11 thermal conductivity moisture humidity energy conservation energy efficiency housing insulation walls autoclaved aerated concrete blocks construction https://engstroy.spbstu.ru/article/2020.96.11/

RAR RUS 138-156 57207875063 https://orcid.org/0000-0002-6637-5708 Northeast Forestry University Wedatalla Afaf ff_osman@yahoo.com

Harbin, China

https://orcid.org/0000-0002-1932-7041 Northeast Forestry University Yanmin Jia jiayanmin@nefu.edu.cn

Harbin, China

The effect of simulated ambient conditions on durability of concrete This study aimed to assess the impact of ambient conditions on the internal microstructure of high-strength concrete (HSC) samples. A scanning electron microscope (SEM) was used with X-ray microanalysis to study the relationship between ambient conditions and the durability of concrete. The concrete specimens were cast at a temperature of 25 ±1 °C and cured under three different conditions: standard curing, steam curing, and dry curing at 50 °C. Conventional Portland cement, crushed aggregate, and natural sand were used in the production of all specimens. Three water binder ratios were typically used: 0.3, 0.35, and 0.4. Three different mixes were also used, containing different binders: 450, 520, and 480 kg/m³. In this study, 30 % fly ash was used in all mixes, while silica fume partly replaced this in a ratio of 0 %, 5 %, and 10 % by weight of cement in the concrete mixes, respectively. Additionally, the effect of ambient conditions was estimated by computing the compressive strength, flexural strength, microhardness, permeability, and the microstructure of concrete. The relationship between these concrete properties was obtained. SEM and energy-dispersive X-ray spectroscopy (EDX) were used to confirm the results for samples cured under all conditions. HSC was obtained that exhibited desirable properties when additional cement materials such as silica and fly ash were used to form homogeneous concrete with a smooth surface; the concrete had low permeability and high durability. It was concluded that it was possible to produce concrete with low permeability and durability within a harsh environment. 10.18720/MCE.96.12 high-strength concrete concrete permeability fly ash silica fume concrete durability https://engstroy.spbstu.ru/article/2020.96.12/