Improving the reliability and durability of sidewalks, footways, car parks and areas for various purposes, made of concrete paving blocks (CPBs), is an important task of construction. In order to improve the quality characteristics, new pavements consisting of concrete paving blocks with a ribbed underside surface are proposed. Hypotheses about the advantages of the developed structural solutions of pavements relative to traditional pavements of blocks with a flat underside surface were formulated. To confirm the hypotheses, studies of one of the developed pavement variants of in laboratory conditions were performed. The article describes the plan and methodology for implementation two series of experiments. In the first series of the experiment, a section of a traditional pavement of concrete blocks with a flat underside surface was investigated, in the second, a section from a pavement of concrete paving blocks with a ribbed underside surface consisting of three prismatic elements. Qualitative characteristics of the pavement are determined by various indexes. As a result of laboratory tests, the dynamics of settlement of experimental CPBs under the influence of vertically applied load was studied, and density index of a sand structural layer located under the tested CPBs was also obtained. The settlement indexes of the tested CPBs were investigated for three days. A comparative analysis of the experimental results confirmed the hypothesis about the advantages of pavements of concrete paving blocks with a ribbed underside surface. For the further implementation of the developed pavement variant in the construction industry, additional research is required. Further research directions of pavements of concrete paving blocks with a modified geometric shape of the underside surface are determined.
The article considers the study of the effect of plasma electrolytic processing on the tribotechnical characteristics of medium-carbon steel. Friction tests were carried out in dry friction mode. Electron microscope and profilometer were used to study the friction tracks. For a comprehensive assessment of the quality of the modified surface layer, the Kragelsky-Kombalov complex parameter was calculated. It was found that plasma electrolytic treatment leads to a decrease in the coefficient of friction and weight wear in comparison with hardened and untreated steel. It has been determined that the mechanism of wear of samples after plasma electrolytic treatment is fatigue wear at boundary friction and plastic contact.
The article presents one of the possible options for solving an urgent engineering problem of the development of special devices and their arrangement in high-rise buildings with continuous facade systems for the possibility of their service. The authors have developed a bracket design in two modifications made of metal plates, which is fastened to the end of a monolithic reinforced concrete slab at the level and along the perimeter of the eaves of the building with chemical anchors of the Hilti HVU series. The nature of the change in the stress-strain state in the plates, main pipes, and in anchor devices of the developed bracket construction was studied by calculation using the usual engineering method, as well as in the generated model in the SOFiSTiK computational and graphic complex. The results of short-term load testing of completed samples of the developed model before serial production are presented. The work of the elements of the developed structures of the brackets under the conditions of the action of an aggressive environment has been analyzed.
In real conditions, bearing elements of metal structures are often subjected to the effect, both external loads, and various aggressive medium, under the influence of which corrosion processes are developed. Corrosive processes with prolonged action lead to a decrease the working area of the welds and accordingly connected elements. During the examination of the technical condition of existing metal structures operating in aggressive medium, it is often necessary to perform calculations to define the reserve of strength. In case of exhaustion of material strength it is necessary to develop measures to strengthen certain weakened elements. Herewith, the quantitative assessment of the reduction of the reliability of welds remains a matter that requires additional research. To study the change in the ratio of squares of metal elements under the influence of the prolonged action of various aggressive medium, specially directed experimental studies were carried out. The results of studies allowed to determine the reserves of the strength of the welded elements in relation to the welds themselves. The ability to determine the reliability of welds depending on the reduction of the area of the welded metal elements increases the operational reliability of metal structures, which for a long time are exploited in aggressive medium.
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