AlfaBuild

RAR RUS 2701-2701 H-9967-2013 16412815600 0000-0002-8588-3871 Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

0000-0003-1398-462X Moscow Power Engineering Institute Dai Qiao 228441531@qq.com

Moscow, Russian Federation

Analytical dependence of the natural oscillation frequency of the planar truss on the number of panels The object of the study is a regular statically determinate beam-type planar truss with double supports and a rise in the middle of the span. The truss lattice is triangular. The stiffness of all truss rods is assumed to be the same. Method. The problem of the lower limit of the fundamental frequency of natural oscillations is solved in analytical form for an arbitrary number of panels. It is assumed that the truss mass is located at the nodes of the truss. The solution of the problem was found in the Maple computer mathematical system using the induction method. The forces in the rods are determined by the method of cutting nodes. The stiffness of the structure is calculated by the Maxwell-Mohr formula. Results. Formulas are obtained for the boundaries of the fundamental frequency of a type polynomial in the number of panels. A distinctive feature of the obtained solution compared to similar solutions using the Dunkerley and Rayleigh estimates is its high accuracy. It is shown that the redistribution of masses along the truss belts little changes the value of the first frequency. 10.57728/ALF.27.1 69 Truss Dunkerley method Rayleigh method Fundamental frequency Induction Maple Mass redistribution https://alfabuild.spbstu.ru/article/2023.27.1/ 2701.pdf

RAR RUS 2702-2702 0000-0002-1418-9858 Yaroslavl State Technical University Balushkin Alexander Leonidovich albalush@mail.ru

Russian Federation,Yaroslavl, Moskovsky av. 88

Control of the deformation process of bending reinforced concrete elements with organized defects The object of the study is non-crack-resistant bending reinforced concrete elements in which, during manufacture in a stretched zone, during operation, a system of discrete initial defects is organized in the form of slots or notches. This procedure aims to give the cracking process an organized character, which will decrease deflections and the width of normal cracks. Method. A model has been developed for estimating the parameters of the stress-strain state for elements with initial notches, which considers the occurrence of significant distortions in the diagram of relative deformations of concrete in the zone directly adjacent to the deformation concentrators. Results. The numerical data of the calculation illustrate the results obtained in the form of resolving equations, the distribution of relative deformations in the section, and the bending stiffness. The data of the performed calculations generally confirm the experimental results obtained on beams and hollow-core slabs with initially organized defects in the form of slots. 10.57728/ALF.27.2 69 Stress and strain concentration factors Initially organized defect Cracking Bending moment-curvature diagram https://alfabuild.spbstu.ru/article/2023.27.2/ 2702.pdf

RAR RUS 2703-2703 H-9967-2013 16412815600 0000-0002-8588-3871 Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

0000-0001-6602-7749 Sun Jia Xuan Kinematic analysis, spectrum of natural frequencies, and formula for the first frequency of a planar truss The object of research is the statically determinate regular symmetrical rectangular beam truss with a double lattice fixed on two supports. The lower chord of the structure is curvilinear, with a rise in the middle of the span. The mass of the lattice is distributed over its nodes. Method. A kinematic analysis reveals the variability of the lattice for a certain number of panels. In this case, an algorithm for searching for the distribution of virtual velocities of lattice nodes is described. Using the Maple computer mathematics system, a formula is derived for the dependence of the lower estimate of the first frequency of natural oscillations of the structure on the number of panels from the range of acceptable values. The result agrees with the numerical calculation considering all degrees of freedom of the structure. It is shown that with an increase in the number of panels, the accuracy of the analytical solution increases. Spectral constants are found in the frequency spectrum of a family of regular trusses. 10.57728/ALF.27.3 69 Truss Natural oscillation frequency Induction Maple Planar truss Dunkerley method Oscillation spectrum https://alfabuild.spbstu.ru/article/2023.27.3/ 2703.pdf

RAR RUS 2704-2704 0000-0002-3142-6018 Kirsanova Tatiana Aleksandrovna 89094001052@mail.ru 0009-0001-6785-1366 Krupenin Fedor Romanovich theoharicot@yandex.ru 0000-0003-3389-7742 Peter the Great St. Petersburg Polytechnic University Shinkareva Maria Konstantinovna shinkareva_mk@spbstu.ru Economic efficiency of the use of self-lifting formwork and inventory formwork in high-rise construction The object of research is the building of the National Space Center in Moscow. Method. During research, the provisions of system analysis, methods of expert assessments, risk theory, methods of economic and mathematical modeling, simulation modeling, comparative method, method of generalization, abstraction, induction, and deduction were used. Results. The analysis of theoretical sources and calculated data based on the project of a high–rise construction object was carried out, because of which the criteria for the characteristics of the object were established, providing conditions for the economically profitable use of self–lifting formwork, and a financial and economic model for justifying investments in this project was built. The benefit of building high-rise buildings in a specific example using self-lifting formwork was approximately 1.3 times. This circumstance justifies the economic benefit of using self-lifting formwork for the construction of the core of a high-rise building. 10.57728/ALF.27.4 69 Economic justification Economics in construction Formwork Self–lifting formwork Construction Load–bearing structure High–rise construction https://alfabuild.spbstu.ru/article/2023.27.4/ 2704.pdf

RAR RUS 2705-2705 0000-0003-3675-5870 Baranov Aleksey Olegovich 0000-0002-2292-3573 Odnodvortsev Dmitry Sergeevich 0009-0002-0073-5771 Novoselov Dmitry Artemovich 0009-0003-2051-9184 Konstantinova Alexandra Andreevna 0009-0001-1523-9597 Lyubomirova Elena Evgenievna The influence of freeze-thaw methods on the frost resistance of concrete paving flags The object of research is the concrete of single layer and double layer paving flags made by vibropressing technology. The purpose of this work is to study the effect of freezing and thawing methods on the frost resistance of concrete paving flags. Method. In this work, some samples of paving flags were subjected to freezing and thawing from all sides and the other part through one side (other surfaces of the specimen were thermally insulated). The frost resistance was evaluated by the measurement of mass scaled from the top surface of samples after 20 freeze–thaw cycles. Results. The obtained results allow us to conclude that the method of freezing and thawing exposure has a significant effect on the frost resistance of concrete. The freezing and thawing through one side of samples led to the appearance of temperature gradients along the height of the paving flags, which model more severe operating conditions than freezing and thawing from all sides of samples. 10.57728/ALF.27.5 69 Concrete Paving flags Frost resistance Freezing and thawing Frost damages Scaling https://alfabuild.spbstu.ru/article/2023.27.5/ 2705.pdf