33407 2304-6295 3 108 2023 1-60

RAR RUS 10801-10801 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

Simplified Dunkerley method for estimating the first oscillation frequency of a regular truss The object of study is a planar statically determinate truss with descending braces in the lattice. The task is to obtain a simplified formula for the dependence of the first natural oscillation frequency of the truss on the number of panels. It is assumed that the mass of the truss is concentrated in its nodes. The nodes perform vertical vibrations, the stiffness of all truss rods, including rods that model supports, is the same. Method. To determine the forces in the elements, the knot cutting method is used. The rigidity of the structure is calculated using the Maxwell – Mohr formula. The sum included in the Dunkerley method is replaced by an approximate formula, which greatly simplifies the solution. Results. A simple formula is obtained for estimating the first vibration frequency of a truss with an arbitrary number of panels. It is shown that the accuracy of the proposed method is higher than the accuracy of the original Dunkerley method and increases with the number of panels. 10.4123/CUBS.108.1 69 Truss Induction Maple Natural frequency Dunkerley method Approximate solution Lower estimate Simplified method https://unistroy.spbstu.ru/article/2023.108.1/ 10801.pdf

RAR RUS 10802-10802 0009-0006-8525-9725 Peter the Great St. Petersburg Polytechnic University Bashkarev Albert Yakovlevich bashkarev@spbstu.ru

Saint Petersburg, Russian Federation

0000-0003-1942-5562 Peter the Great St. Petersburg Polytechnic University Bessonova Victoria Yurievna bessonova.viktoria@yandex.ru 0000-0002-5616-1191 Peter the Great St. Petersburg Polytechnic University Lazarev Yuriy Georgievich lazarev-yurij@yandex.ru

Saint Petersburg, Russian Federation

0000-0002-9514-9136 Lozhechko Viktor Petrovich vplozhechko@mail.ru Interfacial layers in mineral-bitumen composite and durability of asphalt concrete The strength and durability of asphalt concrete are directly related to the adhesive properties of the bitumen. The destruction of asphalt concrete occurs at the boundaries of its mineral fractions’ connection, i.e., at the adhesive connection. The object of the study is the adhesion strength of bitumen and granite in asphalt concrete. The research method is based on the thermofluctuation theory of strength. The initial increase in adhesion strength can be explained by the fact that during the thermal degradation of bitumen molecules, other active radicals appear to create adhesion bonds. At the same time, there is a process of thermal degradation not only of bitumen but also of the adhesive bonds formed. It is confirmed that the destruction of asphalt concrete occurs at the boundaries of the connection of its mineral fractions, i.e., at the adhesive bond. The character of fracture can be cohesive, but the strength of bitumen at the boundary with the surface of mineral fractions and in the free state significantly differs. Thus, we can conclude that choosing the correct temperature-time technological regime can significantly increase the initial adhesive strength of the formed asphalt concrete. According to calculations, this will also provide an increase in its durability. 10.4123/CUBS.108.2 69 Asphalt concrete Bitumen Granite Adhesion Strength https://unistroy.spbstu.ru/article/2023.108.2/ 10802.pdf

RAR RUS 10803-10803 Lesovik Valery Stanislavovich naukavs@mail.ru Popov Dmitry Yurievich popov.dmitry412@yandex.ru N-6730-2017 57199850188 0000-0002-2279-1240 Far Eastern Federal University Fediuk Roman Sergeevich roman44@yandex.ru

Vladivostok, Russian Federation

E-6426-2019 56434340300 0000-0002-5694-1737 Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russian Federation Usanova Kseniia Iurevna plml@mail.ru

St. Petersburg, Russian Federation

Composite binders with superabsorbent polymers The object of research is a composite binder with superabsorbent polymers. The work aims to research the combined action of composite binders and superabsorbent polymers. Methods. The particle sizes distribution of the composite binder was studied by laser granulometry. The fresh properties of the mix were determined by examining the slump flow. The average density was calculated by dividing the mass of the sample by its volume. The compressive strength was studied under a static load on the press on samples with a rib of 70 mm at 3, 7, and 28 days of age. Results. Obtaining polymineral composite binders was carried out by joint grinding of Portland cement CEM I 42.5 N and wet magnetic separation (WMS) waste to a specific surface area of ≈ 550 m2/kg in a vibration mill, followed by the introduction of pre-ground Opoka-like marl (Ssp ≈ 700 m2/kg) used as a mineral modifier. Joint grinding of cement and WMS waste in different percentages and introducing the optimal amount of a mineral modifier made it possible to identify the effect of the composition on the compressive strength. When tested on the 28th day of hardening of the compositions CB-3 and CB-2, an increase in the compressive strength by 82.2 and 60.3%, respectively, was found, while in the composition of CB-1, there was a decrease in the compressive strength by 14.5%. As a result of joint grinding to an equal specific surface, despite the different ratios of components and their hardness, an almost equal grain composition of polymineral composite binders was achieved. Taking into account the increase in the strength of the developed compositions of polymineral composite binders, optimized by the chemical modifier, and the losses caused by the introduction of SAP into the cement system, the effectiveness of the use of CB-2 and CB-3, due to strength compensation, in combination with SAP modification B3 ( 10.4123/CUBS.108.3 69 Concretes Composite Binder Superabsorbent Strength Polymer https://unistroy.spbstu.ru/article/2023.108.3/ 10803.pdf

RAR RUS 10804-10804 B-4397-2014 56826013600 0000-0003-1071-427X Peter the Great St. Petersburg Polytechnic University Gravit Marina Viktorovna marina.gravit@mail.ru

St. Petersburg, Russian Federation

0000-0003-4394-0791 Institute of Computational Modelling of the Siberian Branch of the RAS Kirik Ekaterina Sergeevna kirik@icm.krasn.ru

Krasnoyarsk, Russian Federation

0000-0002-6155-060X Peter the Great St.Petersburg Polytechnic University Shabunina Daria Evgenievna shabunina_de@spbstu.ru

St.Petersburg, Russian Federation

Karimova Ekaterina Iliasovna karimova.ei@edu.spbstu.ru Khlebnikova Ksenia Aleksandrovna hlebnikova.ka@edu.spbstu.ru Wood-Frame Hotel Building: Fire Curtains and Evacuation Analysis The object of research is the hotel building with wooden panel structures. The work aims to study the dependence of the dynamics of fire danger versus the design of a 5-story hotel with a wooden construction. Method. «Sigma PB» software package was used to make computer model of the building and for simulations (spread of fire and evacuation). Cases (scenarios) were formulated, and the spread of fire danger factors  and evacuation under fire conditions were simulated. Results. A significant influence of space design and the time of the start of evacuation on the evacuation conditions were shown. The main danger to people is smoke generated by burning combustible materials (furniture, devices, clothes) in the building during evacuation. The material of the wooden structures of the building at this stage does not pose a danger to people, the building does not lose its strength, and the escape routes do not undergo geometric changes during the evacuation period. An unfavorable scenario of non-compliance with the conditions for unhindered and timely evacuation due to smoke was considered. A use of fire curtain was simulated to limit the spread of danger fire factors. It has been shown that an EI 15 fire resistance rating is sufficient to ensure safe evacuation. 10.4123/CUBS.108.4 69 Fire curtains Fire safety Fire hazards Evacuation Wooden construction https://unistroy.spbstu.ru/article/2023.108.4/ 10804.pdf

RAR RUS 10805-10805 57195684636 0000-0001-8800-2657 Voronezh State Technical University Slavcheva Galina Stanislavovna gslavcheva@yandex.ru

Voronezh, Russian Federation

Britvina Ekaterina Alekseevna esolovieva@vgasu.vrn.ru Shvedova Mariia Aleksandrovna marishwedowa@mail.ru 3D-printable concrete with specific decorative and technological properties The object of research is a 3D-printable decorative concrete. The effect of the cement type and the iron oxide pigment dosage on the setting kinetics and heat release as the significant characteristic of 3D-built printable mixtures has been investigated. Materials and Methods. Two types of 3D-built printable mixtures have been used. Their mix design was regulated by the kind of cement (gray CEM I 42.5 and white CEM I 52.5 R) with the different content of the  phase and dosage of the pigment. The inorganic synthetic pigment based on Fe2O3 oxide was used. The setting kinetic was studied by the penetrometric method. The heat release was controlled using a contact alcohol thermometer. The X-ray and SEM-microscopy methods were used to evaluate the microstructure and hydrate phase composition. The plasticity and shape stability were carried out based on the results of squeeze rheometry methods. The compressive strength was measured according to Russian State Standard GOST 10180-2012 "Concretes. Methods for strength determination using reference specimens". Results. The setting kinetic of 3D-built printable mixtures depends on a combination of cement type and iron oxide pigment dosage. The heat release depends on the iron oxide pigment dosage because the combination aluminate phase of metakaolin and iron oxide pigment in the mix determines the acceleration of hydration phase formation. The temperature increases 1.2 - 1.3 times and 2.5 – 2.7 times for gray cement-based and white cement-based systems, respectively. The combination of a high-strength white cement (CEM I 52.5 R) with a highly active aluminosilicate modifier and iron oxide pigment causes a technologically unacceptable setting reduction. As a result, the open time of white cement-based mixtures is 15 min. Conclusion. The high heat release and fast setting kinetic lead to a technologically unacceptable acceleration of the setting process and open time reduction. The mix design of 3D-build printable mixtures must be based on setting process control. 10.4123/CUBS.108.5 69 Additive manufacturing 3D-printing Decorative mixtures Iron oxide pigment Technological properties Open time Heat release Setting kinetics https://unistroy.spbstu.ru/article/2023.108.5/ 10805.pdf