EXPERIMENTAL INVESTIGATION OF INTERNAL FRICTION IN RUBBER CONCRETE AND FIBER-REINFORCED RUBBER CONCRETE

Statement of the problem. The paper is devoted to the experimental identification of damping for such materials as butadiene rubber (BR) and cis-butadiene low-molecular weight rubber (SKDN-N) based concrete and fiber-reinforced rubber concrete by means of the Impulse Excitation Technique (IET). Results. It was found that BR based concrete with or without fiber-reinforcement shows more obvious viscoelastic properties than the corresponding materials based on SKDN-N rubber. The addition of steel fiber reduces internal friction in the material, while propylene fiber has the opposite effect. This is due to the fact that the fibrous propylene acts as an additional damping material, which enhances energy dissipation under dynamic loading.Conclusion. The internal friction in the rubber concrete and fiber-reinforced rubber concrete was measured for the first time. The obtained data are the additional microstructural characteristics of polymer concrete, which describes its viscosity. The real values of the investigated quantities have been determined, which makes it possible to use the models with fractional derivatives in the calculations of building structures made of rubber concrete and fiber-reinforced rubber concrete for dynamic loads, taking into account the phenomenon of viscoelasticity.

ANALYSIS OF NONLINEAR STATIC-DYNAMIC DEFORMATION OF REINFORCED CONCRETE FRAMES IN OUT-OF-LIMIT STATES

Statement of the problem. The article presents a computational model, an algorithm for computational analysis and the results of calculating the nonlinear static-dynamic deformation of reinforced concrete frames in out-of-limit states caused by the sudden removal of one of the supporting structures. Results. To design a numerical model of the static-dynamic loading mode of a structural system, the LS-DYNA software package was used that makes use of a detailed 3D model implementing an explicit finite element method. During the computational analysis, the physical and mechanical characteristics of the deformation of materials were taken in three variants: those obtained based on the experimental data by G. A. Geniev, the experimental data by N. V. Fedorova and M. D. Medyankin under the static-dynamic uniaxial testing mode of a limited number of standard samples of prisms and according to the Russian standards SP (СП) 385.1325800.2018. Conclusions. Numerical analysis of the static-dynamic deformation of the reinforced concrete framerod system of a multi-storey building has established that the differentiated accounting of the quantitative value of the concrete viscosity modulus and, accordingly, the time and level of static-dynamic loading of the structure allows one to identify the criteria for the special limit state of the elements of reinforced concrete structural systems of buildings and structures in a more rigid manner.

REDUCTION OF THE BIM DIMENSION OF THE FULL LIFE CYCLE OF BUILDING AND FACILITIES

Statement of the problem. The subject of the research is information models of a complete life project in the sector of architecture, design and construction and maintenance of buildings and structures. The purpose of the research is to optimize BIM technologies by building a model based on a discrete vector data description. Results. Analyzed the main obstacles to the widespread introduction of BIM technologies and procedures for the full life cycle of a construction project in the practice of the construction complex of the Russian Federation throughout the entire life cycle of the project, including the stages of construction, operation and disposal, as well as global trends in this process. The method of BIM dimension reduction based on discrete vector data description is formulated. The technology of forming a hierarchical dynamically added and updated information base BIM, taking into account the possibility of its aggregation, has been developed. The algorithms proposed in this work are implemented in the shell of a relational database management system. Conclusions. BIM dimension reduction, based on a discrete vector description of data, allows youto completely solve the problems of both designing and updating the BIM information base, and its transfer between project participants. BIM data formats are determined by the stage of the complete project life cycle. Fully functional for the stage of determining the scope of work on a project, BIM is one-dimensional and is simply determined by the vector of clusters of a lower degree of integration, which allows you to completely overcome all obstacles to the widespread introduction of BIM technologies and procedures of the full life cycle of a construction project into practice. The optimal shell for the implementation of BIM technologies is relational databases.

BEHAVIOUR OF TERNARY BLENDED CEMENT CONCRETE SLAB WITH STEEL FIBER UNDER IMPACT LOADING

Statement of the problem. An experimental investigation of impact strength of ternary blended cement concrete slab with steel fiber under impact loading was carried out. The amount of replacement of binder with Fly ash varies from 10 to 30 % in step of 10 %, glass powder from 20 to 40 % in step of 10 % and fiber volume fraction from 0.75 to 2.25 % in step of 0.75 %. Parametric performance of ten 600 × 600 mm, 60 mm thick reinforced concrete slabs was evaluated. The impact test on the slab was conducted by dropping a steel ball from a height of 457 mm under impact setup. The parameters like failure mode, the impact energy of first crack and ultimate crack failure, ductility index, failure pattern, ultimate crack resistance, crack resistance ratio were investigated when subjected to impact load. Results. The test results reported that the slab specimen S7 shows better performance in strength.

THERMOSETTING BINDER FOR FIBROUS INSULATING MATERIALS

Statement of the problem. The modernization of insulation systems if engineering structures, including pipelines and industrial facilities, is aimed both at solving the general problems of energy efficiency, as well as the particular tasks of heat saving and environmental safety. In this regard, the development and use of a binder that cures at much lower temperatures and does not contain phenols is an urgent task. Results. An experiment conducted to assess the effect on adhesion to various surfaces of a complex binder, cured in the temperature range from 80 to 140 °C, allowed us to determine the optimal flow rate of the latent component and modifier, which were respectively 3.6--4.0 % and 2.6±0.1 % by weight of a binder at an optimal heat treatment temperature of 100 °C. The calculation established that when switching from heat treatment at 250 °C to heat treatment at 100 °C, direct heat costs are reduced by 60 %, and energy costs for the manufacture of mineral wool cylinders by 20--30 %. Conclusion . The possibility of using epoxy glue on latent hardeners as a binder for highly porous systems with the distribution and curing of this binder on thin mineral fibers was justified theoretically and confirmed experimentally. The characteristic parameters of the curing process were determined, the duration of which decreases with increasing temperature and the content of latent hardener.

URBAN ENVIRONMENT DESIGN: NEW METHODOLOGICAL APPROACHES BASED ON THE BIOSPHERE COMPATIBILITY PARADIGM (PART 2)

Statement of the problem. New challenges of our time significantly affect the methodology of urban planning. The development of new principles of city life, regulating the biosphere compatibility of cities and the development of human capital, should be considered an urgent scientific task that requires identifying the patterns of functioning of urban elements of planning structures (residential areas). Results. The paper develops the methodological foundations of urban planning, design and evaluation of design options for residential planning units of the city (quarter, neighborhood, residential area) on the principles of the paradigm of biosphere compatibility of cities and settlements that develop people. A conceptual model of the functional and planning organization of the territory- the hierarchy of city functions - is proposed. An algorithm for evaluating variants of residential area planning projects based on the index of urban function provision has been developed. For each of the functions of the city, the necessary and sufficient composition of indicators for evaluating design decisions is identified. The article discusses the prospect of quantifying the social well-being of the population of residential areas of a biosphere-compatible city as an alternative condition for the formation of a comfortable urban environment.Conclusion. The numerical evaluation of the design solution and a comparative analysis of the level of favorability of a residential neighborhood using the principles of the biosphere compatibility paradigm show what changes are required in the composition of urban planning solutions not only to achieve the quality of the material environment of life, but also human development in all respects.

FRESH PROPERTIES AND MIX DESIGN FOR 3D-PRINTABLE DECORATIVE CONCRETE

Statement of the problem. This paper present the rheological properties of 3D-printable decorative concrete. The effects of mix proportion on its plasticity and shape stability are presented together. It has been established that kind of cement changes plasticity of fresh mixtures and its resistance to load during the printing. Results. The fresh mixtures of 3D-printable decorative concrete with effective mix design had plastic yield value Ki 1.0 - 2.2 kPa, structural strength σ0 = 1.5 - 4.5 kPa, value of plastic deformations Δpl = 0.03 - 0.07 mm/mm. That is defined the ability of these mixtures to plastically deform without structure destruction and hold its shape, resist the deformation under compressions load during multi-layer casting.Conclusions. Shape stability of 3D-printable mixture can be changed by 2--3 times by using cement with efficient ranging of a particle size. The plasticity and shape stability of fresh mixtures can be regulated with usage of viscosity modifiers, the type of which depends on the type of cement.

DEVELOPMENT OF A METHODOLOGYFOR DETERMINING THE BEST OPTION FOR THE ROUTE OF THE HEAT NETWORK AT THE INITIAL DESIGN STAGE

Statement of the problem. Choosing the best option for the route of the thermal network at the initial stage of design is a complex multifactorial task, in addition, due to the lack of a number of necessary design calculations, its solution is accompanied by a limited set of initial data. Thus, it becomes relevant to develop a new methodology for designing the optimal route of the heat supply system considering the qualitative and quantitative characteristics of the discussed object.Results. A mathematical model of a generalized additive vector optimality criterion has been developed, taking into account the material consumption of the heat network, its reliability, construction time, annual thermal losses, heat turnover and temperature dispersion at the consumer. A method is proposed for determining the best option for the route of a thermal network at the initial design stage by jointly solving the optimization problem using vector optimization and matrix generalization methods. The expediency of the joint application of the methods of pairwise comparison and vector optimization in solving the problem under consideration is noted.Conclusions. An important characteristic of the developed mathematical model of the generalized criterion is the possibility of obtaining a more accurate solution to the optimization problem under consideration with an uneven distribution of the heat load by means of a biased estimate of the temperature variance among consumers. A combination of the methods of matrix generalization, pairwise comparison and vector optimization can improve the accuracy of the calculation while solving the optimization problem of choosing the best route of the thermal network.

NUMERICAL SIMULATION OF AERODYNAMIC STABILITY OF LONG-SPAN BRIDGES

Statement of the problem. The aim of the work is to simulate the resonant vibrations of the continuous beam span of the bridge in the direction perpendicular to the wind flow by the finite element method. The article deals with a non-standard situation that arose on May 20, 2010 on the bridge over the Volga River in the city of Volgograd.Results. As a result, an effective algorithm for calculating the aerodynamic stability of large-span bridge structures was developed using one of the most widespread software systems in Russia and neighboring countries - "Lira-SAPR". Recommendations for the selection and modeling of dampers are given. Conclusions. The developed algorithm makes it possible to numerically describe the disturbing force of periodic breakdown of wind flow vortices, which causes resonant oscillations of bridge spans, to apply this force to the design model in Lira-SAPR, and to obtain parameters that make it possible to assess the stress-strain state of the system during oscillations and to select the optimal characteristics of the damping devices.

ENGINEERING METHOD FOR CALCULATING THE TEMPERATURE ON THE INNER SURFACE OF THE OUTER CORNER OF A BUILDING

Statement of the problem. The temperature on the inner surface of the outer corner is always lower than on the inner surface of the outer wall. This temperature difference might lead to the formation of condensation on the inner surface of the wall at low outdoor temperatures. Therefore the problem of developing an engineering method for calculating the temperature in the outer corner to exclude the possibility of condensation on the inner surface in the design process of the outer wall structures is extremely relevant. Results. To address this problem, based on solving the heat balance equation, taking into account the amplitude of air temperature fluctuations in the room and heat absorption of the inner surfaces of walls, intermediate bottoms (ceiling and floor surfaces), parting walls, a formula was obtained to calculate the temperature on the inner surface of the outer corner. Also, during the study, natural tests of the wall structure with an outer corner were carried out and the temperatures on the inner and outer surfaces were obtained.Conclusions. Comparison of the calculation results using the developed engineering calculation method and experimental data showed that the temperatures on the inner surface of the outer corner almost coincided. This makes it possible to use the suggested engineering method for calculating the temperature on the inner surface of the outer wall corner in the design of enclosing structures to exclude the appearance of condensation.