33407 2304-6295 2 107 2023 1-60

RAR RUS 10701-10701 57210972600 0000-0001-6472-9413 Kazan State University of Architecture and Engineering (KSUAE) Shmelev Gennady Nikolaevich gn.shmelev@mail.ru

Russian Federation, Tatarstan republic, Kazan, Zelenaya Str., 1

0000-0003-2662-6020 Khaidarov Lenar Ilnurovich haidarov_lenar@mail.ru 0000-0001-7920-9920 Galimullin Ilshat Albertovich e.guliash@yandex.ru 0000-0002-0205-0859 Shishkanov Danil Gennadievich Influence of wind load on connection system of temporary towers The objects of research are temporary demountable towers. When a wind load is applied to a structure at an angle, an uneven horizontal wind load occurs, which causes the structure to twist. For capital construction projects, due to the massiveness and greater rigidity of the nodes, this is not significant, but for light structures, accounting for this effect is very important. The purpose of the work is to study the connections of such towers and the influence of wind load unevenness on them. Method. Wind load studies are conducted, based on a model of a diving tower with the dimensions of the widest part 12 x 10 m and a height of 28 m. Different methods of calculation are taken into consideration, including the ones based on regulatory documentation and numerical modeling. Software packages allow calculating models with higher accuracy and less time, facilitating manual counting and reducing the probability of error. A gas-dynamic calculation is performed, as a result of which the aerodynamic coefficients are found.  Results. A comparative analysis of two methods for calculating wind loads is carried out, after which measures are suggested to increase the load-bearing capacity of the structure. 10.4123/CUBS.107.1 69 Connection system Wind load Numerical modeling Experiment Design model Construction https://unistroy.spbstu.ru/article/2023.107.1/ 10701.pdf

RAR RUS 10702-10702 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

0000-0002-6848-0974 Moscow Power Engineering Institute Luong Cong Luan luongcongluan96@gmail.com

Moscow, Russian Federation

Frequency spectrum of natural oscillations of the spatial structure of the rod pyramid The object of the study is a pyramid-type enclosure statically defined in space. The truss has support posts along the contour of the base. The corner buttons are fixed on the support sphere, cylinder, and bracket. Structure with axes of symmetry. The purpose of the study is to give formulas on the dependence of the deflection under the effect of uniform load and the first natural frequency of oscillation on the number of plates, size and mass concentrated at the nodes of truss. Method. By using equilibrium equations at the nodes it is possible to find the forces in the truss elements. The system of equations also includes the responses of the vertical supports located along the contour of the truss structure. From this, it can be concluded that the force distribution on the truss rods does not depend on the number of plates. The deflection and stiffness values of the truss structure are calculated according to the Maxwell–Mohr formula. The lower analytical estimate of the first frequency was obtained using the Dunkerley method. All mathematical transformations are performed in the Maple symbolic mathematics system. The dependence of the solution on the number of panels is obtained by generalizing a series of solutions for structures with a successively increasing number of panels. Results. The value of the first natural frequency is compared with the numerical solution obtained by analyzing the entire spectrum of natural frequencies of the vertical oscillations of the system of masses located in the truss nodes. The frequency equation is compiled and solved using the eigenvalue search operators in the Maple system. The natural frequency spectrum of the truss is analyzed. 10.4123/CUBS.107.2 69 Deflection Pyramids Induction Maple Natural frequency Dunkerley method Spectra of natural frequencies https://unistroy.spbstu.ru/article/2023.107.2/ 10702.pdf

RAR RUS 10703-10703 P-3728-2017 57194112309 0000-0001-6184-2365 Vyatka State University Tyukalov Yury Yakovlevich yutvgu@mail.ru

Kirov, Russian Federation

GMW-6276-2022 0000-0002-3884-874X Vyatka State University Ashikhmin Stanislav Eduardovich ashihminstanislav@gmail.com

Kirov, Russian Federation

Quickly constructed joint of precast concrete arch elements The object of research is the design and stress–strain state of the precast concrete element’s rigid connection. For connection, composite rods are used, which are glued into prepared holes and channels. The reinforced concrete elements are connected by rods vertically and horizontally. In addition, for more uniform stresses transfer, polyurethane sheets are installed at the element’s joint. Method. To analyze the stress-strain state of the precast concrete element’s connection, a flat finite element model is used. The quadrangular physically non-linear finite elements are used for concrete modeling. For calculations, a non-linear stress-strain diagram for concrete, given in the regulatory documents for the reinforced concrete structures design, was applied. The deformation diagram of steel reinforcement is elastic-plastic. Composite rods are deforming elastically. The polyurethane sheets were modeled by nonlinear two-node finite elements working in compression and shear. Results. The quickly constructed structure for connecting precast concrete elements is proposed. A numerical analysis of the stress-strain state of such a connection is performed using the example of calculating the beam and the bridge arch. The comparison of the strength and rigidity of prefabricated and corresponding monolithic structures was made. 10.4123/CUBS.107.3 69 Precast concrete elements Quickly constructed joint Composite rods Epoxy adhesive Physical nonlinearity Block arch https://unistroy.spbstu.ru/article/2023.107.3/ 10703.pdf

RAR RUS 10704-10704 57219014392 0000-0003-3675-5870 Peter the Great St. Petersburg Polytechnic University Baranov Aleksey Olegovich aleksey.o.baranov@yandex.ru

St. Petersburg, Russian Federation

Strakhov Dmitry Aleksandrovich sdaleks2008@rambler.ru Creep of High Strength Concrete at Elevated Temperatures The object of research is a high-strength concrete containing silica fume, fly ash, and superplasticizer. This work aims to obtain experimental data on the creep strain of high-strength concrete at elevated temperatures and develop the expression for the description of creep strain (the specific creep strain) of high-strength concrete at elevated temperatures. Method. The creep of high-strength concrete at elevated temperatures was studied on not drying samples. Samples of high-strength concrete at the age of 90 days were heated at a rate of 10-15 ° C / hour to temperatures of 90 and 200°C and then loaded a constant load of 30% of the compressive strength of the test specimens determined at the age of 28 days. Results. The experimental studies confirmed other authors' conclusions that the creep strain increases with an increase in the temperature of heating. The creep strain at temperatures of 90 and 200°C by the end of the time under consideration was 3.6 and 4 times higher than the creep strain at a normal temperature of 20°C. 10.4123/CUBS.107.4 69 High strength concrete Temperature Creep Specific creep strain Fly ash Silica fume https://unistroy.spbstu.ru/article/2023.107.4/ 10704.pdf

RAR RUS 10705-10705 12039592100 0000-0003-4283-0400 South Ural State University Korolev Aleksandr Sergeevich korolev@sc74.ru

Chelyabinsk, Russian Federation

Koroleva Yulia Igorevna korol_14@mail.ru 0009-0004-3908-0260 Gusev Dmitrij Denisovich Wood (arbolit) concrete for bearing span structures The object of research is a wood (arbolit) concrete for bearing span structures. The purpose of this work is to analyze the empirical structural, mechanical and deformative properties of constructive arbolit standard samples and reinforced beams in comparison with results of design model calculation. Method. The experimental and computational methods were used in the research. The following necessary parameters for the exploiting load calculation model were tested by the standard methods: compressive and tensile strength, compressive and tensile modulus of elasticity (MoE) of arbolit with D600-D1300 density, B1.5-B5 class. The following significant in design mechanical and deformative properties of reinforced arbolit model beams were tested by 4-point bending test: reinforcement’s stress, beams’ bending moment and deflection under bending load.  Results. The experimental data have demonstrated the changing of the tensile stress in beams’ reinforcement under bending load depending on the arbolit’s MoE. The model of this dependence was determined. The application of this model has provided high accuracy of arbolit reinforced beams’ bending moment calculation. 10.4123/CUBS.107.5 69 Wood Arbolit Concrete Wood Concrete Reinforced Concrete Strength Elasticity Span Structures Constitutive models Stress-strain curves Static loads https://unistroy.spbstu.ru/article/2023.107.5/ 10705.pdf