Key Engineering Materials Vol. 828

Abstract: Nowdays, the creation of many new and modern architectural structures, modernization of historical and cultural monuments, and the acquisition of new architectural solutions have become possible thanks to the use of new technologies and new construction materials. The discovery of transparent polymer materials in the architectural and construction industry allowed not only to achieve significant lightweight of the buildings but also to create unique and innovative forms for structures and architectural environments. The use of ETFE (ethylene tetrafluoroethylene) plastic material, which is already a widely used polymer material, is quite perspective in the global and Armenian construction fields. Based on the series of researches and a number of already constructed architectural solutions in international practice, it is clear that the studied material will solve a number of issues for the preservation of the environment and individual structures, that will enable to preserve the established Armenian architecture with contemporary approaches, with a significant contribution in the formulation process of contemporary architecture. In addition, the use of the above-mentioned material in the design process of the new architectural structures can create interesting combinations of traditional and modern forms, in the design of a individual structures, as well as in the formation of separate structures of the architectural complexes by applying the advantages and disadvantages associated with the aesthetic and functional properties of the materials.

Abstract: For Armenia, the main criterion of reliability and durability of buildings is the level of their seismic resistance. The experience of the 1988 Spitak devastating earthquake showed that the only type of apartment buildings that did not collapse and did not cause any loss of life or material damage were large paneled houses, which were designed for lower levels of seismic impact. In spite of the undeniable fact of high seismic stability and effective technical and economic indicators given in the article, further, due to low heat-insulating indicators of applied wall protection panels and limited spans up to 6m, the construction of such buildings in the republic was gradually reduced and has already undeservedly reached almost complete cessation. In this regard, it should be noted that at present there are already a lot of highly effective thermal insulation materials and technologies that allow to easily solve this problem of external walls and get large paneled buildings with a high level of energy saving. As for the limitation of spans, it cannot be considered a decisive factor, because spans up to 6m are quite acceptable for the construction of social apartment buildings. 80% of the population has a strong demand for such housing. The country has an acute shortage of affordable, high-seismic safe houses and this is especially acute now in the Spitak earthquake zone, where after more than 30 years, many still live in temporary houses. We believe that the construction of large-panel buildings would have solved this problem long ago. From all given it is possible to conclude that modernization according to achievements of a science and revival of large-panel housing construction for republic has quite reasonable technical-economic and town-planning basis.

Abstract: The paper presents a numerical analysis for the end-plate bolted connection of beams to the column. Three models of the node were considered (with a non-reinforced column web and with reinforcement in the form of stiffening and reinforcement by welding an overlay on one side of the web. The values of strains and stresses for the analysed solutions were compared. It was shown that for the adopted load, it is necessary to increase the load-carrying capacity and stiffness of the web panel in order to ensure safe operation of the joint. The results of the analysis indicated that both solutions for web panel reinforcement are correct: strains and stresses in the node do not exceed the permissible values.

Abstract: In this paper, we consider the problem of determining the basic characteristics of the stress state of a composite in the form of a piecewise homogeneous elastic layer reinforced along its extreme edges by stringers of finite lengths and containing a collinear system of an arbitrary number of cracks at the junction line of heterogeneous materials. It is assumed that stringers along their longitudinal edges are loaded with tangential forces, and along their vertical edges - with horizontal concentrated forces. In addition, the cracks are laden with distributed tangential forces of different intensities. The case is also considered when the lower edge of the composite layer is free from the stringer and rigidly clamped. It is believed that under the action of these loads, the composite layer in the direction of one of the coordinate axes is in conditions of anti-flat deformation (longitudinal shift). Using the Fourier integral transform, the solution of the problem is reduced to solving a system of singular integral equations (SIE) of three equations. The solution of this system is obtained by a well-known numerical-analytical method for solving the SIE using Gauss quadrature formulas by the use of the Chebyshev nodes. As a result, the solution of the original system of SIE is reduced to the solution of the system of systems of linear algebraic equations (SLAE). Various special cases are considered, when the defining SIE and the SLAE of the task are greatly simplified, which will make it possible to carry out a detailed numerical analysis and identify patterns of change in the characteristics of the tasks.

Abstract: Increasing attention is paid to noise control and provision of the required acoustic comfort. This is due to an increase in the noise of the environment, the concentration of people in the cities, development of industry, transport and aviation. Currently, mass construction does not have the necessary number of sound-proof products and this demand is constantly increasing. Therefore, the development of new efficient sound-proof products, especially on the base of industrial waste, is of particular importance. While separating obsidian during the production of rubble and sand from lithoid pumice and perlite - it turns into a waste product. With the expansion of obsidian with grain sizes from 5 to 20 mm in a duration of 3-10 minutes at temperatures from 1050 to 1150⁰С, it is possible to obtain a lightweight porous material with the lowest average density of 200–350 kg/m³ (in a piece of stone) and thereby solve environmental issues - to recycle production wastes. The requirements for mechanical strength and decorativeness of sound-absorbing materials are increased, since they are used for tiling internal walls, so they must have low water absorption capacity, low hygroscopicity, and be fire and bio resistant. On the base of expanded obsidian, it is possible to obtain acoustic materials: cellular concrete and plasters with cement and gypsum with an average bending strength of 2.229 and 5.679, and 6.2095 and 12.670 MPa for compression.

Abstract: At the present stage of urban fabric formation, the problem of adapting existing buildings to modern socio-economic conditions and functional needs is very important. In the conditions of constraint of already existing urban development, the issue of reconstruction and renovation of existing buildings becomes particularly relevant. There are frequent examples of new additions and superstructures over the “historical foundation”. In the light of the solution of functional and especially constructive tasks, the choice of building materials becomes extremely important. Examples of reconstructed buildings have been considered, it has been revealed that the most used in the reconstruction of modern materials for today are glass and composite panels. Since the reconstructed buildings are mainly built of stone or brick, the building and composite panels with color and texture features contrast with the old masonry, thereby highlighting and complementing it. The quality and characteristics of the above mentioned materials, the advantages that they have in comparison with traditional stone and concrete, and the great possibilities of obtaining a variety of structures and facade plastics have been analyzed.

Abstract: The work relates to introduce the quality improvement of construction materials, in particular the enrichment of macadam which is one of the main constituents of concrete. The proposed technology improves the quality of the concrete without essential equipment transformation. As a result, the broken stone acquires physic-mechanical and qualitative new properties, increases concrete strength, and decreases the unit of cement in concrete consumption.

Abstract: In the formulation of thermoelasticity and in the framework of the conventional theory of thermal stresses, the problem on the stress state of an elastic piecewise-homogeneous plane or an infinite plate at non-uniform steady-state heating is considered. On the interface of dissimilar materials, the compound plane is reinforced by a collinear system of absolutely rigid thin inclusions and is subjected to mechanical and thermal influences. First, to determine the temperature distribution in a piecewise-homogeneous plane the corresponding boundary value problem of the theory of steady-state heat conduction is solved using the integral Fourier transform. Solving this problem is reduced to solving a singular integral equation (SIE) that allows an exact solution. Further, the elastic displacements of points of the compound plane, caused by mechanical and temperature influence, are determined by the known methods of thermoselasticity. Based on these results, solving the problem of the contact interaction between the system of inclusions and a compound plane is again reduced to solving SIE, which also allows an exact solution. A special case is considered.

Abstract: A mathematical model has been proposed for processing data from tests of building materials and obtaining optimal links between the characteristics of the bearing capacity and technological parameters of building materials for the use of these connections in refined design and construction procedures for building structures. To improve the accuracy of the results obtained, a three-level optimization principle was applied using the least squares method and a computational algorithm was compiled that allows us to develop an additional computational subroutine expanding the capabilities of the corresponding standard computer programs.

Abstract: A method for processing data from tests of building materials is proposed in order to identify the optimal functional relationships between the physicomechanical characteristics and the technological parameters of building materials. The least squares method (MLS) was used and to improve the accuracy of calculations, a three-level optimization of calculations was introduced using groups of transforming functions (180 items). Taking into account the increased volume of statistical computations, computer subroutines have been developed, which, together with standard MLS computational programs, make it possible to realize the choice of the indicated optimal functional connections.