33407 2304-6295 1 99 2022 1-60

RAR RUS 9901-9901 0000-0001-7287-1145 Southwest State University Solodilova Viktoriia Andreevna bbty@yandex.ru

50 Let Oktyabrya Street, 94, Kursk, Russia

0000-0003-1951-7299 OBU "Design Institute of Civil Engineering, planning and development of cities and towns "Kurskgrazhdanproekt Dubrakova Ksenia Olegovna Dko1988@yandex.ru

Dimitrova street,96/1, Kursk, Russia

7005346094 0000-0003-4261-9840 Southwest State University Bulgakov Alexey Grigor’evich agi.bulgakov@gmail.com

50 let October St. 94, 305040 Kursk, Russia

A-7827-2017 56662851300 0000-0001-8407-8144 Ogarev Mordovia State University Erofeev Vladimir Trofimovich yerofeevvt@mail.ru

Bolshevistskaya St., 68, Saransk, Russian Federation

0000-0001-7157-2143 Technical University of Dresden Otto, J. Otto, Jens jens.otto@tu-dresden.de

Mommsen Str. 10, 01062 Dresden, Germany

Fire resistance of statically indeterminate steel systems The object of research is a single-span metal frame. Since the fire resistance of metal-bearing structures is insignificant, this is because at temperatures above 400 °C for steels and more than 200 °C for aluminium alloys, significant development of plastic deformations under constant load (creep) begins to manifest itself. The purpose of this work is to conduct research aimed at studying various emergency impacts, in particular, the impacts associated with heating during a fire and its effect on the stability of both individual elements and the entire structural system. To meet the new requirements of Federal Law "Technical Regulations on the safety of buildings and structures". To identify the influence of the heating temperature of the gas medium on the mechanical characteristics of steel structures by obtaining data from the accepted regularity and constructing a trend line and by the method of displacements, taking into account kinematic definiteness, to investigate the effect of temperature at uniform heating during a fire on the value of critical parameters of a single-span frame. By solving some problems that arose during the study, we can say about the necessity to improve steel structures to prevent irreversible consequences during an emergency. The research's main results are to identify the relationship between the temperature of the medium on the mechanical characteristics of steel structures. 10.4123/CUBS.99.1 69 Fire resistance steel structures statically undetectable systems emergency defects https://unistroy.spbstu.ru/article/2022.99.1/

RAR RUS 9902-9902 6506150284 0000-0003-1139-3164 Moscow State University of Civil Engineering Sainov Mikhail Petrovich mp_sainov@mail.ru

Moscow, Russian Federation

57204501403 0000-0003-4277-7128 Moscow State University of Civil Engineering Soroka Vladislav Borisovich

Moscow, Russian Federation

J-8425-2019 57194142918 0000-0002-1151-0853 SASTRA Deemed University Gunasekaran Murali murali@civil.sasta.edu

Thanjavur, India

Combination of rockfill dam reinforced concrete face and seepage control wall in the foundation: stress-strain state Introduction. Construction of reinforced concrete face rockfill dams on soil foundations requires solving the problem of arranging a safe diagram of conjugation between a dam reinforced concrete face and a seepage control structure in the foundation. The object of research is the Miaojiaba dam, 111 m high (Gansu, China), which in the channel part rests on a huge layer of soil base, and in the side sections is located on rocks. Materials and Methods. Stress-strain state (SSS) of a reinforced concrete face (CF) and a cutoff wall (COW) of the considered dam was studied with the aid of numerical modeling. The study was conducted in 2D and 3D formulations. Finite elements with high degree of approximation inside the elements are to be used for modeling of thin-wall structures. Results. By the results of numerical modeling the CF and COW are subject to complicated deformations and are in a complicated stress state. It is characterized by presence of considerable compressive forces both in the face and in the wall. Nevertheless, compressive forces do not exceed the limit compressive strength of concrete. Tensile stresses are more dangerous for strength of seepage control structures. In the face the tensile stresses appear in the zone of conjugation with rock foundation. COW is subject to tension in the zone of rest on a stiff concrete apron. Besides, COW separates from rock sides. All this creates the danger of failure of seepage control protection tightness. Conclusions. At designing rockfill dams with combination of a reinforced concrete face and a seepage control wall a special attention should be paid to spatial conditions of these elements’ performance. This will help in finding the zone of appearance of dangerous stresses, which are not seen at solving a 2D problem. However, it is evident that conjugation of CF with COW with the aid of a stiff concrete apron is not a safe solution. 10.4123/CUBS.99.2 69 Stress-strain state rockfill dam concrete face soil foundation strain cut-off wall seepage-control wall https://unistroy.spbstu.ru/article/2022.99.2/ 9902.pdf

RAR RUS 9903-9903 AAE-3259-2020 56296687300 0000-0002-2299-3096 Peter the Great St. Petersburg Polytechnic University Rybakov Vladimir Alexandrovich fishermanoff@mail.ru

St. Petersburg, Russian Federation

57216911588 0000-0003-2067-5585 Technische Universität Dresden Jos Vladislav Andreevich jos_vlad@mail.ru

Dresden, Germany

Stress State of Г-Shaped Thin-Walled Rod Joints in Bending Torsion The paper is devoted to the study of constrained torsion in joints of flat thin-walled rod systems. The goal of the work is to analyze the stress state of finite stiffness joints made of two thin-walled open-profile rods with different parameters, which are under conditions of bending torsion (The object of research), and to determine the corresponding rotation coefficient. Method. The main research method in the paper is the finite element method. The software program ABAQUS is used in order to design and calculate 1-D and 3-D finite element models of various joints and structures made of thin-walled profiles. Results. The areas of application of previously known hypotheses were determined: the hypothesis of A.R. Tusnin; the hypothesis of A.S. Gorodetsky and others. By the design and calculations of 3-D finite element models, the behaviour of the bimoment transmission was investigated in the joints made of thin-walled profiles: with different stiffness; connected at different angles; taking into account structural elements (gusset plate, corners, bolted connections). The recommended values of the “coefficient of the cross-sectional axis rotation” in the joints made of thin-walled profiles connected at the angle of 90˚ were determined. It is shown the existence of an angle between the profiles of the Г-shaped connection, at which the rotation coefficient is equal to zero, which in turn demonstrates the absence of the bimoment transmission in the joint. 10.4123/CUBS.99.3 69 Lightweight gauge steel structures Bending torsion Plane frames Thin-wall rods Rigid joint Bimoment Warping Stresses https://unistroy.spbstu.ru/article/2022.99.3/ 9903_1.pdf

RAR RUS 9904-9904 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

Model of a spatial dome cover. Deformations and oscillation frequency The object of research. A new scheme of a statically determinate spatial truss is considered. The design has a hexagonal dome resting on two belts. The belts are supported by vertical racks. Two corner supports have spherical and cylindrical hinges. The outer support contra consists of 6n  horizontal rods, the inner one consists of 6(n-1) rods. The contours are connected by skews. Formulas are derived for the deflection of the vertex and the angular hinge depending on n. The upper and lower analytical estimates of the first frequency of natural oscillations of the structure are found. Method. Calculation of the forces in the rods is carried out by cutting out the nodes from the solution of the system of equilibrium equations for all nodes in the projection on the coordinate axes. To derive formulas for the dependence of breakdowns, forces, and the frequency of free oscillations, an inductive generalization of the sequence of solutions for structures with a different number of panels is used. The structural stiffness matrix and deflection are calculated using the Maxwell - Mohr formula in analytical form. To find estimates of the lowest frequency of vibrations of nodes endowed with masses, the Dunkerley and Rayleigh methods are used. Results. The vertical load distributed over the nodes and the concentrated load applied to the top are considered. Formulas for the forces in the characteristic bars of the structure are derived. A picture of the distribution of forces throughout the structure is presented. The resulting formulas for the deflection and frequency estimates have a compact form. The upper estimate of the first oscillation frequency of nodes under the assumption of vertical displacements of points has fairly high accuracy. The analytical solution is compared with the lowest oscillation frequency obtained numerically. All analytical transformations are performed in the Maple symbolic mathematics system. Some asymptotics of solutions is found. 10.4123/CUBS.99.4 69 Spatial truss Vibrations frequency Maple Analytical solution Deflection Induction Rayleigh method Dunkerley method Asymptotics Maxwell-Mohr formula https://unistroy.spbstu.ru/article/2022.99.4/