HYDRODYNAMICAL INSTABILITY OF NEWTONIAN FLOW BEFORE AN AXISYMMETRIC SUDDEN CONTRACTION

The sizes of the vortex region before the axisymmetric sudden contraction of the circular pipe at the Newtonian flow have been investigated. Area ratios 0.250 and 0.500 were considered. The sizes of the vortex region have the extreme dependence with a maximum at the transition of the laminar flow into a turbulent flow one. When the Reynolds number at the laminar flow increase, these sizes also increase, and they decrease at the turbulent flow. In both cases, the sizes of the vortex region are proportional to the Reynolds number. A transition region between laminar flow and turbulent flow lies in the range of the Reynolds number from 3000 to 5300 and 750…1300, determined by the diameter of a bigger pipe of sudden expansion and a step height correspondingly

PROSPECTS OF USING POLYMERIC MATERIALS IN THE CONSTRUCTION OF SOLAR COLLECTORS

The solar energy that reaches the Earth is free, but installations to convert solar energy into heat, as well as equipment for transporting and storage that heat, require some investment. A significant part of the components of these systems are metals. Pipelines in solar collectors and heat exchangers are made of copper, aluminum is used for the absorber and housing, and the steel is often used in heat storage tanks. One of the options to reduce the cost of solar collectors and increase their efficiency is to use polymeric materials instead of metals. The main advantages of using polymeric materials in solar thermal collectors are their cost, especially if you are taking into account the growth of the renewable energy market and rising prices for metal . The use of polymers also reduces the costs of production, transportation and installation for the user.

THEORETICAL ANALYSIS OF EXISTING CONCEPTS TO EVALUATE THE NON-FAILURE OF RC STRUCTURES IN OPERATION

The article presents a theoretical analysis of existing concepts to evaluate the non-failure of RC structures in operation. To perform the analysis, the authors considered a number of scientific works of both Ukrainian and foreign researchers. The main focus was on works in which the model of the stochastic nature of the RC structure operation included random parameters of acting loads, as well as the reserve of its bearing capacity and serviceability (geometric dimensions of cross sections of constructive members, strength and deformation characteristics of materials, etc.). Among others, according to the authors, important problems in terms of analysis of a single work were the volume of statistical selection of random parameters, their number and impact on the study result, as well as rationality of the adopted method of calculating the probability of failure (or non-failure work) of RC structure in operation. Based on the processing of a number of scientific works, the authors highlight the relevance, advantages and disadvantages of the concepts of non-failure assessment proposed there, as well as the formulate the conclusions and recommendations for further experimental and theoretical research in this area.

INNOVATIVE METHOD OF NITRIFICATION AND DENITRIFICATION ON THE EXAMPLE OF WASTEWATER TREATMENT PLANT OF KOLOMYIA

The article is devoted to the unsatisfactory operation of biological wastewater treatment plants. At present in Ukraine there are no developments of equipment and devices to ensure the operation of treatment facilities using the technology of nitridenitrification of deep wastewater treatment from nitrogen and phosphorus compounds. The analysis of the equipment of biological treatment systems - nitri treatment plant - denitrifier, clarifier tanks is carried out. At the same time, the standards of the degree of purification of both Ukraine and the European Union were taken into account. On the example of treatment facilities in Kolomyia, Ivano-Frankovsk region, modern schemes of biological wastewater treatment for the removal of nitrogen and phosphorus have been proposed, namely, the re-equipment of single-corridor aerotanks into bioreactors of nitridenitrifiers by creating zones with different oxygen conditions in their volume.

NUMERICAL ANALYSIS FOR COMPRESSED CERAMIC HOLLOW BRICK MASONRY COLUMNS STRENGTHENED WITH GFRP MESHES

This article presents the analysis of obtained experimental results for the study of masonry columns which have been strengthened by GFRP confinement after high-level axial compression loading. Ceramic hollow-brick middle-scale models were investigated regarding assumed testing program. The basics of experimental studies were briefly described in the paper. Theoretical study was performed to compare experimental and theoretical values. Such numerical analysis helps to evaluate the possibility to use the existing standard`s approaches for calculating bearing capacity of strengthened by GFRP jacketing ceramic brick columns which were subjected to the high axial loading. Theoretical results areratheraligned with experimental data. Some conclusions were provided in terms of usability the analytical model provided standards and other scientists. Addressing to the further investigation and research problems were performed.

ENERGY SAVING OF MODULAR BUILDINGS WITH THE HELP OF BIOGAS TECHNOLOGIES

Ukraine has significant land resources for agriculture and is able to provide its population not only with food but also with raw materials for bioenergy. The article presents a graph of heat capacities and the distribution of heat flows in a bioreactor. The dependences for determining the heat fluxes of flat and cylindrical surfaces are presented. The article outlines the present state of utilization of fallen leaves of trees. The method of utilization by anaerobic fermentation is proposed. The design of bioreactors and the main factors influencing the methane formation process are considered. The methodology for calculating the biogas production process is presented. The productivity of the bioreactor has been determined, depending on the temperature of the raw material and the time of hydraulic resistance

INVESTIGATION OF THE PROCESS OF MODIFICATION OF PETROLEUM ROAD BITUMEN BY MALEIC ANHYDRIDE

The possibility of modification of oxidized petroleum bitumen 70/100 produced by JSC "Ukrtatnafta" (Kremenchuk, Ukraine) with maleic anhydride was studied. The influence of maleic anhydride amount, process duration, and temperature on the main physical and mechanical characteristics of modified bitumen was studied. The optimal amount of maleic anhydride introduction to bitumen was established. It is found that 2 wt. % maleic anhydride allows to increase the softening temperature of the modified bitumen (from 46 °C to 52 °C). Adhesion to crushed stone also increases (from 2.5 points to 4.5 points) and other indicators improve. Sufficient time to modify the bitumen with maleic anhydride was 30 minutes. The optimum modification temperature for obtaining the modified bitumen with maleic anhydride is 130 °C. Increasing the temperature of the modification has a negative effect on the final physical and mechanical properties of the binder.

METHODS FOR DETERMINATION OF DEFORMATIONS WITH THE USE OF DIGITAL IMAGE CORRELATION TECHNOLOGIES

In order to obtain reliable information about the stress-strain state of the structure, subjected to loading, it is necessary to determine deformations` distribution. In some cases, it is almost impossible to assess stress-strain state with the traditional approaches. However, the DIC methods provide reliable information about the fields of displacement and deformation almost without limitations. Such approaches are rather effective for determination of the stress-strain state on smooth surfaces and in zones with stress concentrators. The DIC method is based on the comparison of the intensity of speckle pictures` distribution of optically rough surfaces. The combination of the intensities of correlation peaks with the corresponding calculation algorithms at the subpixel level makes it possible to obtain high measurement accuracy with simpler hardware compared to electronic interferometry technologies. The main purpose of this work is the detailed analysis of techniques and methods for determination of deformations with the use of digital image correlation. The article includes detailed review of existing studies of this topic and description of main principles for analytical computation of the optical data.

REGULATION OF STRESS-DEFORMED STATE IN COMPRESSED ELEMENTS OF STEEL FRAMES

The article is devoted to the regulation of the stress-strain state in the compressed elements of steel frames under full operating load. It is proposed to perform reinforcement of such elements with different end eccentricities of load application by rational regulation of the stress-strain state in the reinforcement elements. It is shown that the use of SDS adjustment for frame racks increases their bearing capacity and reduces deformability and welds. The new proposed technology of SDS regulation and possible constructive decisions are offered. Numerical experiment revealed high efficiency of application of the proposed solutions during the reconstruction and reinforcement of the metal frame system. The implementation of the proposed method of SDS regulation confirmed its effectiveness.

ESIGNING OF ALKALINE ACTIVATED CEMENTING MATRIX OF ENGINEERED CEMENTITIOUS COMPOSITES

The development of high-performance materials, which are characterized by high compressive and flexural strength, durability and performance properties, is an urgent problem of modern construction. Engineered cementitious composites are one such material. Improving of properties of composites is achieved by partial replacement of cement with supplementary cementitious materials. The ratio of binder and filler components and superplasticizer consumption were selected. The optimal ratio of cement:fly ash:sand is 1:1:1 and the dosage of polycarboxylate superplasticizer is 0.75% by weight of the binder. The reduction of the negative impact of the increased amount of fly ash, which is characterized by low reactivity, is provided by the introduction of metakaolin and alkaline hardening activator. Alkaline activated cement system is characterized by increasing of the early strength in 1.5 times comparison with equivalent mixture without alkaline activator. Strength of alkaline activated cementing matrix after 28 days is 66.1 MPa and specific strength Rc2/Rc28 is 0.61.