33407 2304-6295 6 104 2022 1-60

RAR RUS 10401-10401 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

Trihedral Rod Pyramid: Deformations and Natural Vibration Frequencies The object of research is a new truss scheme of a statically determinate dome structure. The purpose of the study is to derive formulas for the dependences of the deflection under the action of a uniform load and the first frequency of natural vibrations on the number of panels, sizes, and masses concentrated in the truss nodes. Method. The forces in the truss rods are found from the equilibrium equations of the nodes. The system of equations also includes the reactions of vertical supports located along the contour of the structure. It is shown that the distribution of forces over the structure rods does not depend on the number of panels. The deflection values ​​and stiffness of the truss structure are calculated using the Maxwell – Mohr formula. The lower analytical estimate of the first frequency is obtained by the Dunkerley method, the upper one by the Rayleigh energy method. As a form of truss deflection in the Rayleigh method, the deflection from the action of a uniformly distributed load is taken. Only vertical oscillations of the weights are assumed. Results. The dependence of the solution on the number of panels is obtained by generalizing a series of solutions for trusses with a successively increasing number of panels. The solution uses operators of the Maple computer mathematics system. Graphs of the dependence of the deflection on the number of panels for different truss heights are plotted. The horizontal asymptote of the solution of the deflection problem is found. The value for the first natural frequency is compared with the numerical solution obtained from the analysis of the entire spectrum of natural frequencies of the vertical oscillations of the mass system located in the truss nodes. The frequency equation is compiled and solved using the eigenvalue search operators in the Maple system. It is shown that the lower analytical estimate based on the calculation of partial frequencies differs from the numerical solution by no more than 37%, while the upper estimate has an error of 7%. In this case, the formula for the lower Dunkerley frequency estimate turns out to be more compact. The natural frequency spectrum of the truss is analyzed. Isolines were found in the set of frequencies for a series of regular trusses. 10.4123/CUBS.104.1 69 Spatial truss; Trihedral dome; Natural vibrations; Lower frequency bound; Upper frequency bound; Dunkerley method; Maple; Induction; Frequency spectrum isoline; Rayleigh formula https://unistroy.spbstu.ru/article/2022.104.1/ 10401.pdf

RAR RUS 10402-10402 0000-0003-4242-4234 Nizhny Novgorod State University of Architecture and Civil Engineering Bodrov Mikhail Valerevich

Nizhny Novgorod, Russian Federation

0000-0003-1904-708X Nizhny Novgorod State University of Architecture and Civil Engineering Smykov Aleksandr Anatolevich

Nizhny Novgorod, Russian Federation

Energy efficiency of radiant heating systems based on water emitting profiles The use of energy efficient heating systems is justified by the current economic conditions, one of the types of such systems are radiant heating systems. The most energy-efficient solution is the use of gas infrared emitters, in this case, there is no intermediate heating medium, and the heat of combustion of the gas enters the premises, but this solution has a few restrictions on the availability of natural gas, comfort, and fire hazard. The object of research is water infrared emitters, which can be emitting panels or profiles using an intermediate coolant, but do not have many of the limitations inherent in gas systems. A common problem for all types of radiant heating is the lack of a scientifically grounded and generally accepted engineering methodology for its design, and most of the regulatory documents simply do not consider the peculiarities of the operation of radiant heating systems and, thus, do not allow a few its advantages to be realized. This research was carried out based on Nizhny Novgorod State University of Architecture and Civil Engineering (NNGASU) Radiant Heating Laboratory, unique in Russia. Method. For a comprehensive study of the model of a radiant heating system based on water infrared emitters, a number of laboratory and field experiments were conducted: study of the thermal characteristics of a water infrared emitter; study of the radiant characteristics of a water infrared emitter; study of the thermal regime in rooms with heating systems based on water infrared emitters; study of the temperature regime in rooms equipped with radiant heating systems based on water infrared emitters; investigation of the thermal regime of external enclosing structures in rooms with heating systems based on water infrared radiation. Results. Laboratory tests of water radiant heating systems have shown their high efficiency, and the data obtained during the research formed the basis of "Recommendations for the design of radiant heating systems based on water infrared emitters", which are essentially an engineering methodology for calculating the thermal regime of premises for various purposes. 10.4123/CUBS.104.2 69 Thermal physics; Radiant heating; Water heating; Infrared radiation; Emitter; Energy efficiency https://unistroy.spbstu.ru/article/2022.104.2/ 10402.pdf

RAR RUS 10403-10403 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

Formulas for calculating the deflection and displacement of a planar truss support with short studs in a lattice The calculation of deformations of building structures is usually carried out by the finite element method in numerical form  [1]–[3]. Analytical methods are used much less often in engineering calculations. For regular trusses with periodically repeating structures in the lattice, in [4]–[7], together with operators of computer mathematics systems, the method of induction is used, which makes it possible to derive calculation formulas for an arbitrary order of structure regularity. Problems of regular statically determinate rod systems were dealt with by Hutchinson, R.G. and Fleck, N.A.   [8], [9]. Matrix methods and graph theory in the calculations of regular planar and spatial trusses in relation to their optimization were applied by  Kaveh A. [10]–[12]. In the papers [13]–[18], by induction in the Maple system, solutions were obtained for the problems of deflection of various planar  trusses with an arbitrary number of panels. An analytical estimate of the first natural frequency of oscillations of planar and spatial trusses was found in [19]–[21]. A two-sided estimate of the first frequency of a regular truss in an analytical form using the Maple system was obtained in [22]. The article [23] proposes a two-node method for predicting the effective elastic properties of a periodic cellular truss. The continuum representation for calculating a regular truss is used in [24]. In [25], in the problem of periodic truss networks based on the concepts of the quasi-continuum method, the decomposition of a regular truss lattice into simple Bravais lattices is used. To reduce computational costs while accurately taking into account the dominant deformation mechanisms, a homogenized continuum description of lattice trusses is introduced in [26], based on the application of the Cauchy–Born multilattice rule to a representative unit cell. The author's handbooks [27], [28] contain schemes of planar static determinate trusses and formulas for calculating their deflections and forces in characteristic rods. Analytical methods for calculating a regular truss in relation to the problem of optimization taking into account creep were also used in [29]. 10.4123/CUBS.104.3 69 Planar truss; Maple; Analytical solution; Deflection; Induction; Short studs; Asymptotics https://unistroy.spbstu.ru/article/2022.104.3/ 10403.pdf

RAR RUS 10404-10404 G-1611-2018 56352359500 0000-0002-5156-7352 Volgograd State Technical University Korniyenko Sergey Valeryevich svkorn2009@yandex.ru

Volgograd, Russian Federation

0000-0003-4888-7117 Volgograd State Technical University Dikareva Ekaterina Aleksandrovna Ea.dikareva@gmail.com

Russia, 400005, Volgograd, pr. Lenina, 28

Optical Remote Sensing for Urban Heat Islands Identification The relevance of the problem of studying the mechanisms of urban heat island (UHI) formation is confirmed by a large number of studies around the world. The research demonstrates the identification of UHI by remote sensing (RS) method. The object of research is city of Volgograd (48°42′42″, 44°30′50″); a metropolis located in the southeast of the European part of Russia. Volgograd is a linear city located along the Volga 65–70 km long and about 5 km wide. The climate is temperate continental, arid (according to the International climate classification Köppen — type «Dfa»). Analysis of climate data highlights the need to study UHI during the summer period. Data from the Landsat 8 satellite was used to measure the temperature of the land cover (LC). Satellite images were purchased for various calendar dates: 28.07.2015, 05.08.2018 and 06.08.2021 (about 10 a.m.). The land surface temperature (LST) was calculated in various territorial zones of the city: residential and public-business (mid-rise and multi-storey buildings), residential low-rise buildings, industrial, recreational. Analysis of thermal images is performed by the method of cross-sections. A relative temperature index is proposed, on the basis of which gradations of UHI intensity and ecological qualities of urban environment (UE) are established. According to the results of statistical processing, it was found that the experimental data of satellite thermal images are generally adequate and the conclusions obtained from the results of a small sample can be extended with a probability of 0.95 to the entire hypothetical population. The UHI was identified (with temperature difference about 8.5 K) for the study object. The LC emissivity has been shown to be crucial for determining of LST. The choice of effective building materials, structures and technologies, for example, white and green roofs, play an important role in reducing temperature and mitigation the UHI. The production area gives maximum thermal pollution. The increase in temperature in the mid-storey and multi-storey buildings is explained by the higher heat storage capacity of multi-storey buildings and adjacent areas. Verification of the obtained results demonstrated their consistency with the data available in the scientific literature that confirms the reliability of the present studies. The urbanization process increases the intensity of the UHI and reduces the ecological quality of the UE. UHI mitigation strategies should include a set of architectural, planning, structural and engineering measures. Further research will be devoted to mathematical modeling of simultaneous processes of transient heat and mass exchange of urban areas, taking into account various meteorological parameters (solar radiation, temperature, wind speed, etc.) to assess the UHI and its mitigation during the summer period. 10.4123/CUBS.104.4 69 Urban Planning; Land Cover; Urban Thermal Environment; Urban Heat Island; Urban Thermal Environment Index; Land Surface Temperature; Remote Sensing; Landsat 8; Atmospheric Urban Heat Island; Surface Urban Heat Island https://unistroy.spbstu.ru/article/2022.104.4/ 10404.pdf

RAR RUS 10405-10405 ABD-2048-2021 57205074229 0000-0003-3154-8207 Peter the Great St. Petersburg Polytechnic University Sabri Mohanad Muayad Sabri mohanad.m.sabri@gmail.com

St. Petersburg, Russian Federation

0000-0001-5478-9324 Department of Civil Engineering, COMSATS University Islamabad, Abbottabad Campus Javed Muhammad Faisal Department of Civil Engineering, COMSATS University Islamabad, Abbottabad Campus Muhammad Arslan ars918158@gmail.com Self-Healing Concrete Using Fly Ash, Macro Synthetic Fibres and Recycled Aggregates The development of cracks in concrete can reduce its durability and service life, causing its steel rebar to be exposed to harmful substances from the external environment, eventually leading to strength loss of concrete and high repair costs. Self-healing technique can eradicate the crack spontaneously, likely replacing or decreasing maintenance and repair costs. Self-healing concrete using low calcium Fly Ash with recycled Aggregate (RCA) and macro synthetic fibers is a novel approach to increase durability and serviceability, decreasing repair and maintenance costs. This research intends to create self-healing concrete using different volumes of Fly Ash with partially replaced RCA and macro synthetic fibers and to study the autogenous behavior of Fly Ash. Various volumes of Fly Ash 35%,45%, and 60%, respectively, were used. In addition, the coarse Aggregate was partially replaced with RCA. The results show that replacing RCA with natural Aggregate and using Fly Ash significantly decreased the strength of concrete. Thus, to increase the mechanical properties of concrete macro synthetic fibers were used at two percentages 5% and 1%, respectively. After that, concrete samples were cracked after 28 days of curing, and after 5 weeks, they were cured for autogenous self-healing. The results showed that using Fly Ash from 45-50% gave the optimum healing to cracks in 5 weeks and the use of macro synthetic fibers at 0.5% caused the best improvement in mechanical properties of concrete with good workability. 10.4123/CUBS.104.5 69 Self-Healing; Fly Ash; Macro Synthetic Fibres; Concrete; Healing properties; Mechanical properties https://unistroy.spbstu.ru/article/2022.104.5/ 10405.pdf