33407 2304-6295 3 88 2020 1-50

RAR RUS 8801-8801 AAH-2547-2019 7801686579 0000-0001-7011-8213 Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russian Federation Barabanshchikov Iurii Germanovich ugb@mail.ru

St. Petersburg, Russian Federation

Tashkent Institute of Irrigation and Agricultural Mechanization Engineers, Tashkent, Uzbekistan Popyvanova Zoia Dmitrievna

Tashkent, Uzbekistan

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

0000-0002-2908-4565 Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russian Federation Akimov Stanislav Vasilevich akimov_sv@spbstu.ru

St. Petersburg, Russian Federation

The Effectiveness of Polymer-Paraffin Emulsions to Reduce Moisture Loss from Hardening Concrete The effectiveness of polymer-paraffin emulsions used for applying to the surface of hardening concrete to reduce moisture loss and reduce shrinkage was experimentally evaluated. Six types of moisture-proof coatings were tested in various temperature and humidity conditions, as well as in the presence of wind. Moisture losses from concrete were determined through a protective polymer-paraffin film of various thicknesses. The most effective of the tested ones was Emcoryl BFMK emulsion coating, which allows you to save up to 72-78% moisture from the amount lost by unprotected concrete for 72 hours at a temperature of 20 and 40 ℃ and the corresponding relative humidity of 60 and 30%. After the first 1-3 days of concrete hardening, the evaporation rate through the coatings, regardless of their type and thickness, becomes the same as with the open surface of the concrete. Therefore, coatings inhibit moisture evaporation only in the initial period, after which the evaporation rate is limited by diffusion in concrete. Studies have shown that in the first hours after applying the emulsion, while a solid film is not yet formed, the wind increases moisture loss, but contributes to the rapid drying of the film and a decrease in its vapor permeability. Therefore, an increase in wind speed leads to an overall reduction in moisture loss from concrete. 10.18720/CUBS.88.1 69 concrete hardening moisture loss protective coatings polymer-paraffin emulsions wind speed https://unistroy.spbstu.ru/article/2020.88.1/ 8801-2.pdf

RAR RUS 8802-8802 H-9967-2013 16412815600 0000-0002-8588-3871 National Research University Moscow Power Engineering Institute Kirsanov Mikhail Nikolaevich mpei2004@yandex.ru

Moscow, Russian Federation

Analytical Solution of a Spacer Beam Truss Deflection with an Arbitrary Number of Panels The object of research is a planar statically definable truss with straight belts, a Sprengel-type lattice, and two fixed hinge supports that create external static indeterminability. The purpose of this work is to derive a formula for the dependence of the deflection of the structure in the middle of the span on the number of panels, dimensions, and load. We consider a load evenly distributed over the nodes of the upper belt. Method. To output the calculation formula, the induction method is used. The forces in the rods simultaneously with the four reactions of the supports are determined by cutting out the truss nodes from the solution of the system of equilibrium equations in symbolic form. The deflection is found by the Maxwell-Mohr formula. A series of solutions for trusses with successive increases in the number of panels give sequences of coefficients whose common terms are determined from the solution of homogeneous linear recurrent equations of the ninth order, compiled in the Maple computer mathematics system. Results. The solution for coefficients is polynomial in the number of panels. It is noted that for an odd number of panels, the determinant of the system of equilibrium equations turns to zero, which corresponds to the instantaneous kinematic variability of the structure. Given an appropriate diagram of the possible speeds of the nodes. The graph of the dependence of the dimensionless deflection on the number of panels shows significant jumps in the deflection values, which decrease with the increase in the number of panels. The dependence of the deflection on the ratio of the vertical dimensions of the spangle part and the entire truss significantly depends on the parity of the number of panels. Using Maple, we obtained a linear asymptotic solution for the number of panels, inversely proportional to the span. 10.18720/CUBS.88.2 69 truss Maple deflection asymptotics symbolic solution https://unistroy.spbstu.ru/article/2020.88.2/ 8802.pdf

RAR RUS 8804-8804 57226357829 0000-0003-3166-1576 Peter the Great St. Petersburg Polytechnic University Dmitriev Andrei Nikolaevich dmitriefan@outlook.com

St. Petersburg, Russian Federation

LCC CADFEM CIS Novozhilov Iurii Vladislavovich vatin@mail.ru

St. Petersburg, Russian Federation

6504372981 0000-0002-2011-000X Center of Engineering Physics, Simulation and Analysis, JSC Mikhaliuk Dmitrii Sergeevich dmitry@multiphysics.ru

St. Petersburg, Russian Federation

AAH-3368-2019 56091980300 0000-0003-3850-424X Peter the Great St. Petersburg Polytechnic University Lalin Vladimir Vladimirovich vllalin@yandex.ru

St. Petersburg, Russian Federation

Calibration and Validation of the Menetrey-Willam Constitutive Model for Concrete Flow plasticity theory has been widely used for nonlinear simulation of reinforced concrete (RC) structures. Constitutive relations of flow plasticity theory in CAE software are referred to as material models. One of the most popular concrete models is the Menetrey-Willam model realized in ANSYS software. The Menetrey-Willam constitutive model can well capture many important mechanical behaviors of concrete such as different tensile and compression strength, nonlinear hardening, softening, and dilatancy. However, there is no published calibration methodology with a clear foundation based on structural design standards. This study suggests an effective calibration procedure to identify the input parameters for the Menetrey-Willam model, mainly according to the CEB-FIP Model Code. Firstly, the identified parameters were verified on basic material tests by a single element simulation. Verification revealed full compliance simulation results with the standards for uniaxial compression, uniaxial tension, and biaxial compression stress states. To validate the ability of the material model to objectively reproduce structural behavior we validated it on six structural tests: confined uniaxial compression of a cube specimen, four-point bending test of a RC beam, three-point bending test of a notched concrete beam, eccentric compression of a RC column, shear rupture test and push-off test of an S-shaped specimen. For all structural tests, a mesh sensitivity analysis was also carried out. The use of the proposed model parameters allows to achieve a good match with the experimental data for all the considered problems almost independently of the mesh size. The obtained parameters can be conveniently used for occasional users without special knowledge in the field of concrete mechanics.   10.18720/CUBS.88.4 69 Concretes Calibration Computer simulation Constitutive models Strength Stress-strain curves Static loads Finite element method Plasticity ANSYS https://unistroy.spbstu.ru/article/2020.88.3/ 8804(1).pdf

RAR RUS 8805-8805 57209305847 0000-0002-6692-7971 Institute of Mechanics and Seismic Stability of Structures named after M.T. Urazbaev, Tashkent, Uzbekistan Ismoilova Sabida Isroilovna

Tashkent, Uzbekistan

56527032000 0000-0002-2038-8298 Institute of Mechanics and Seismic Stability of Structures named after M.T. Urazbaev Loginov Pavel Viktorovich

Tashkent, Uzbekistan

57214084613 0000-0003-3648-6594 Tashkent Institute of Irrigation and Agricultural Mechanization Engineers, Tashkent, Uzbekistan Khamidov Saidjon Sobitjon ugli

Tashkent, Uzbekistan

57216550677 0000-0002-2617-6931 Tashkent Institute of Architecture and Civil Engineering, Tashkent, Uzbekistan Kumakov Jakhongir Xamzayevich

Tashkent, Uzbekistan

0000-0002-2392-5845 Institute of Mechanics and Seismic Stability of Structures named after M.T. Urazbaev, Tashkent, Uzbekistan Khazratova Tulganoy Yashin kizi

Tashkent, Uzbekistan

Geotextile-Reinforced Soils in a Modernized Irrigation System The use in irrigation construction of geotextile soils reinforced (strengthened) with fibrous materials, including cotton fibers waste of textile materials, requires strength assessment of these soils under tension and bending. Due to the low tensile and bending strength of soil, the load is born by the fibers reinforcing the soil. Direct methods to test tensile and bending geotextile soils are complex. It was proposed to evaluate the strength of geotextile materials through the strength characteristics of their components. Soils reinforced with textile waste cotton fibers are considered in the paper. To determine the strength of cotton fibers experimentally under the action of friction force only, a tensile test of cotton yarn consisting of cotton fibers was conducted. The diagrams of cotton yarn stretching obtained experimentally and the known diagrams of sandy soil compression are given in the paper. It was found that in the process of strain, both cotton yarn and soil change structurally. These changes are described by the change functions of their strain moduli, determined from considered experimental results in the form of graphs. Based on them, a method for assessing the strength of geotextile soils based on the general law of cotton yarn and soil strain is proposed. The possibility of using the formula obtained from this law for a particular case when determining and evaluating the strength of cotton yarns under tensile forces is shown. Therefore, it is recommended to use this formula in calculating the tensile strength of geotextile soils reinforced (strengthened) with waste textile materials used in innovative and modernized construction of irrigation reservoirs, canals, ditches, and reservoirs. 10.18720/CUBS.88.5 69 Geotextiles Soils Fiber Strength Irrigation construction https://unistroy.spbstu.ru/article/2020.88.4/ 8805.pdf