75504 2712-8172 4 88 2019 1-79

RAR RUS 3-13 Peter the Great St. Petersburg Polytechnic University Le Tu Quang Trung quangtrung1690@gmail.com

29 Politechnicheskaya St., St. Petersburg, 195251, Russia

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

29 Politechnicheskaya St., St. Petersburg, 195251, Russia

Peter the Great St. Petersburg Polytechnic University Bratashov Alexey aleks.kuskus@mail.ru

29 Politechnicheskaya St., St. Petersburg, 195251, Russia

Static accounting of highest modes in problems of structural dynamics The calculation of building structures for dynamic effects is usually performed according to the method of decomposition by its own forms of vibrations. However, the problem is that such a method gives an exact solution of the dynamic problem with full consideration of the entire spectrum of modes. Moreover, when solving practical problems with the use of software systems, dynamic calculations are performed approximately taking into account a limited number of the first natural modes of oscillation. The contribution to the dynamic response of the structure of unaccounted higher forms of oscillations, as a rule, is not evaluated at all. The results show that the error of such a solution to a dynamic problem can be significant. Consequently, this paper is devoted to the method of static registration of higher forms of oscillations in problems of the dynamics of building structures. The description of the main provisions of the method is given, examples of its implementation in the calculation of spatial structures under the action of an external harmonic load are given. With the help of a computational program complex, the displacements of nodes and internal forces in the elements of the structures under consideration are determined. Various parameters of the dynamic effect and the number of vibration modes taken into account were set. The adopted method of static accounting for higher forms of oscillations requires solving one dynamic problem and two auxiliary static problems. An important circumstance of the approach is that one of the static problems should be solved by the method of decomposition in its own forms of vibrations. The approach proposed in the article allows to significantly reduce the computational costs of dynamic calculation in comparison with the classical approach. This result can be of great importance when solving problems for complex dynamic effects and for structures that are not uniform in hardness. 10.18720/MCE.88.1 structural dynamics spectral method vibration modes highest modes static accounting spatial structures https://engstroy.spbstu.ru/article/2019.88.1/ 01.pdf

RAR RUS 14-24 23493671500 Siberian Transport University Shakhov Sergey sashakhov@mail.ru 57194617402 Siberian Transport University Rogova Elena elena.rogova4@yandex.ru Factors affecting the ultrasonic disaggregation of powders Using finely dispersed mineral particles of various origins and morphologies offers a promising strategy in controlling the structure formation in cement composites. However, the use of such additives is hampered because those additives proved to be prone to consolidation into rather dense aggregates. Fine dispersion and disaggregation of powders is possible with the aid of cavitation ultrasonic treatment. However, the optimal conditions for such processing can not be established without conducting simulation studies. The purpose of the present study was the identification of ultrasonic-action factors and conditions ensuring an efficient disaggregation of finely dispersed powders of various origins and particle morphologies. In our study, we used diopside, granulated blastfurnace slag (GBS), wollastonite, ash, and calcium carbonate powders. It is found that the process of ultrasonic treatment of aqueous suspensions is accompanied not only by the dispersion of initial particles and aggregates but, also, by simultaneous formation of new aggregates. That is why the observed variations of the specific surface area and the optical density of powders can be attributed to the variation of the fractional composition of dispersed phase. The activating capability of a mineral additive is due to the fraction of the particles less than 1 μm in size exerting a key influence on the variation of the specific surface area of the powder. Our estimate of the energy efficiency of the cavitation disaggregation of powders during an ultrasonic treatment shows that the most energy-favorable one is the ultrasonic treatment lasting for 1–5 minutes, i.e. during the period of the first half-wave of the variation of the particle fraction less than 1 μm in size. 10.18720/MCE.88.2 ultrasonic cavitation ultrafine additive disaggregation grinding cement construction https://engstroy.spbstu.ru/article/2019.88.2/ 02.pdf

RAR RUS 25-41 6602801860 0000-0001-7532-0074 Penza State University of Architecture and Construction Loganina Valentina loganin@mail.ru Penza State University of Architecture and Construction Petukhova Nadezhda npetukhova58@mail.ru

28 Herman Titov St., Penza, 440028 Russia

57199850188 0000-0002-2279-1240 Far Eastern Federal University Fediuk Roman roman44@yandex.ru

8. Suhanova St. Vladivostok, st. Octyabrskaya. 690950. Russia

57194347544 Far Eastern Federal University Timokhin Roman gera210307@yandex.ru

8. Suhanova St. Vladivostok, st. Octyabrskaya. 690950. Russia

Polystyrene paint with reduced contents of volatile compounds The proposed organomineral additives are novel, eco- friendly components for polystyrene paints. A light brown-red loam was used as a filler for polystyrene paints. Rheological, technological and physico-mechanical properties of paints and coatings based on them were studied by a series of standard tests. Characteristics of frost and water resistance, hiding power and holding capacity of polystyrene paint confirmed the creation of durable paints with high performance properties. Comprehensive studies have shown that the addition of organic additives in the composition of polystyrene paint increases the critical volume concentration of pigment 1.2 times, increases the degree of grinding paint, reduces dispersion time (2 times) and reduces the speed of shelter from 160 to 112 g / m2. Analysis of the results of experiments showed that the addition of organic additives contributes to increased resistance to external influences, as well as the strength of adhesion to the substrate by 22 %. Using the obtained results will allow you to create polystyrene paints with a low content of volatile compounds and increased crack resistance. 10.18720/MCE.88.3 buildings construction facades organomineral additive polystyrene paint clay volatile organic compounds https://engstroy.spbstu.ru/article/2019.88.3/ 03.pdf

RAR RUS 42-51 57202972366 Krylov State Research Centre Solovev Sergei aerodynamics.spb@gmail.com

44, Moskovskoye shosse, St. Petersburg

57202054286 0000-0002-4050-6298 Peter the Great St. Petersburg Polytechnic University Khrapunov Evgenii hrapunov.evgenii@yandex.ru

29 Politechnicheskaya St., St. Petersburg, 195251, Russia

Modeling of the mean wind loads on structures Correct determination and consideration of wind loads are primary importance in the design of unique architectural objects such as high-rise buildings, sport arenas, airports, large-span bridges. One of the most accurate ways to determine wind loads is to carry out model tests in specialized wind tunnels. Nowadays, during wind tests much attention is paid to the correct modeling of natural wind properties. In present work comparison of the most popular approaches for turbulence length scale determination is presented. One of the purposes of this study is to compare the main aerodynamic characteristics of the simple cube model obtained in uniform flow and during ABL modeling. This paper provides a brief overview of the method for ABL modelling in test section of the Landscape wind tunnel and contains experimental data on mean flow velocity distribution, turbulence intensity, dimensionless spectral density and integral scale of turbulence. The comparison of experimental data obtained for cube model in various wind tunnels revealed the influence of ABL on geometry and intensity of separation zones at the cube sides, and, as consequence, the influence of the same on integral and local aerodynamic characteristics of the object. On the basis of the obtained experimental data, it was concluded that the intensity of the separation zones has significant influence on the total aerodynamic loads, which is usually not taken into account in the framework of applied calculations. The difference in numerical values of aerodynamic characteristics was up to 30 %. 10.18720/MCE.88.4 aerodynamic force on buildings atmospheric boundary layer wind loads physical modeling Silsoe cube wind tunnel pressure coefficient facades https://engstroy.spbstu.ru/article/2019.88.4/ 04.pdf

RAR RUS 52-59 55516020800 Northeast Forestry University Zhao Qianqian 492954791@qq.com

Harbin Heilongjiang, China

55434335600 Northeast Forestry University Cheng Peifeng chengpeifeng@126.com 57204285919 Yellow River Survey Planning and Design Co., Ltd. Wei Yuwei weiyuwei1991@qq.com Harbin Dongan Automobile Engine Manufacturing Co,Ltd. Wang Jianwu nihaone@163.com Factors effecting the recovery process of self-repairing concrete In order to explore the influence of external environmental factors, the initial width of cracks and the placement of glass fiber tubes on the repairing effect of self-repairing concrete, glass fiber tubes are built in self-repairing concrete specimens, Self-repair test using repair adhesive. The repair rate α is characterized by the ratio of the initial crack width l to the time t used for repair completion, and the effects of the above three factors on the repair rate were analyzed. The results show that at –15~30 °C, the repair rate increases with the increase of temperature; at 0~30 °C, the growth rate of repair rate is obviously less than the growth rate of –15~0 °C. When the temperature is below 0 °C, the temperature plays a leading role in the improvement of the repair rate; The repair rate increases first and then decreases with the increase of the initial crack width. When the crack width is from 0.4to 0.6mm, the repair rate increases significantly faster than the crack width from 0.6to 1.0mm. The rate of repair of the crack width from 1.0 to 1.5 mm is significantly higher than that of the crack width from 1.5 mm to 2.0 mm. And when the initial crack width is about 1.0 mm, the repair rate reaches the highest level. When the initial crack width and the repair temperature are between –15 and 30 °C, the repair rate of the glass fiber tube is slightly better than that of the diamond when the inverted trapezoid is placed. The initial width of the crack has the greatest influence on the repair rate. Followed by temperature conditions and placement of fiberglass tubes. The corresponding factor levels at the maximum repair rate are 1.0mm, 30 °C and inverted trapezoids. 10.18720/MCE.88.5 self-repairing cement concrete initial crack width placement method external environment repair rate https://engstroy.spbstu.ru/article/2019.88.5/ 05.pdf

RAR RUS 60-69 55534147800 0000-0001-5290-3429 Southwest State University Kolchunov Vladimir sjs28@mail.ru 57202804437 Southwest State University Dem'yanov Alexey speccompany@gmail.com The modeling method of discrete cracks and rigidity in reinforced concrete Cracks can be quite critical for the safety of architectural structures so their investigation is crucial. Excessive crack opening in reinforced concrete structures leads to corrosion of the reinforcement, which significantly reduces their serviceability. An extraordinary problem on the width of crack opening was considered for RC (reinforced concrete) elements under the affects of bending and torsion. Its solution was proposed on the basis of RC theory involving the hypotheses of fracture mechanics. The initial hypotheses about the formation and disclosure of spatial cracks for multilayer RC structures were formulated. These proposals allowed assessing the resistance of concrete in tension and the distance between the cracks, as well as the width of its disclosure. Hence, specific features of a double-cantilever element adjacent to spatial cracks were investigated with both mathematical calculations and experimental studies. The results demonstrated that developed new technique can be used for estimating the width of the spatial cracks for RC elements under the affects of bending and torsion. 10.18720/MCE.88.6 reinforced concrete crack fault bending-torsional coupling computational models splitting tensile strength https://engstroy.spbstu.ru/article/2019.88.6/ 06.pdf

RAR RUS 70-79 57203962119 0000-0001-9723-5161 National Research Moscow State Civil Engineering University Nguyen Trong-Chuc ntchuc.mta198@gmail.com 57208303308 Tri Dung Construction Transportation Joint Stock Company Luu Xuan Bach xuanbachmta@gmail.com

Dong Nai, Vietnam

Reducing temperature difference in mass concrete by surface insulation The heat which is produced in the cement hydration is rather high in mass concrete structures like dams, pavements, piers. In fact, it takes a longer time to cool the inner of the mass than its surface. The main reason for this result is that having the temperature difference between the hot inner mass and its cooled surface. Such a gap like that is the cause of appearing a large number of cracks in the surface of the mass concrete at several days age. In this study, the application of using a sand-layer insulation to control mass concrete block cracks at an early age. Specifically, these processes are performed by the program Midas Civil 2017 in cases: without sand-layer insulation, and with the application of using sand-layer insulation have thickness in range of 0–7 cm for heat preservation. In conclusion, the results in this study showed that when using an insulation thickness of 7 cm, it led to that the maximum temperature differences between the surface and the center of mass concrete block is lower than the limitation. The recommendations made as a result of this study is that sand-layer insulation should be used to prevent and limit cracks of the mass concrete block at an early age. 10.18720/MCE.88.7 heat of hydration temperature gradient crack mass concrete mathematical model sand-layer insulation. https://engstroy.spbstu.ru/article/2019.88.7/ 07.pdf