Purpose. Experimental dependences "destructive tangential stress – vertical load" has the form of a curvilinear line, which is sometimes called the Coulomb – Mohr envelope. In this case, the Coulomb – Mohr strength criterion gives a value of the destructive tangential stress other than zero, which, in turn, leads to an overestimation of the holding forces when calculating the stability and strength of soil foundations and structures. The analysis showed that the problem of considering physical nonlinearity of the strength properties of clay soils is relevant, and one of the ways to solve it is to use the well-known in the mechanics of soil strength O. Shashenko’s criterion. The purpose of the scientific article is the following – according to the known experimental results of consolidated – drained tests of sandy loam soil in the device of single-plane shear, it is necessary: to perform approximation of experimental data using linear dependence (Coulomb – Mohr strength criterion) and nonlinear dependence (O. Shashenko’s strength criterion); to estimate the accuracy of the approximation using the relative standard error and to extrapolate the approximation results to the region of low pressures. Methodology. According to the relevant recommendations, the properties of soils and their classification were determined. Also, according to the recommendations, the strength of the soil at its natural moisture and when water-saturated were determined. The obtained results are presented in tabular form. Material constants that are included in the Coulomb – Mohr and O. Shashenko’s criteria were determined. The conformity of the strength criteria to the experimental data was evaluated, and extrapolation of these criteria in the field of low pressures was performed. Results. In the field of change of experimental data, the dependence "destructive load – vertical pressure on the soil", established within O. Shashenko’s criterion of strength, has a better fit of the experiment than a similar dependence on the criterion of Coulomb – Mohr. The criterion of soil strength proposed by O. Shashenko can be used to predict the strength of sandy soils. Scientific novelty. Approximation of experimental results of consolidated-drained tests of sandy soil in the device of single-plane shear using the strength criteria of Coulomb – Mohr and O. Shashenko is performed. Practical value. A comparative analysis of the results is carried out and the use of O. Shashenko’s strength criterion for forecasting the strength of sandy soils is substantiated.

Purpose. Methods of metal structures calculation which would take into account sudden changes of the design scheme and its elements destruction as a result, are not perfect enough and are often fragmentary. The research of survivability of multi-element bar structures affected by negative factors will improve the efficiency of the such structures calculation with the prospect of further expanding the possibilities of forecasting the survivability of metal structures depending on its operation conditions. As a research object three-dimensional metal bar structures are considered, which are characterized by a high degree of production significance and responsibility during the operation. Methodology. The considered normative documents do not have a single approach regarding the identification of the problem and technique of generating possible solutions, but they combine all the listed standards. Approaches and methods for assessing the degree of a structure damage or serviceability are somewhat different: in some documents the area of damaged floor structures is limited; in others, the state of structures that have not gone out of work is assessed; as well as the economic forecast of a new building construction or restoring an old one. If we group the normative documents’ provisions of the different countries, we can single out two established approaches on "progressive destruction" protection. According to the first approach, it is necessary to use indirect protection measures, according to the second one, it is necessary to use the ability of key (bearing) elements to perceive damaging effects, the ability of structure to redistribute loads in case of some elements’ failures. Results. To increase the stability of building structures to progressive destruction, metal ones particularly, it is necessary to consider the possibility of local destruction already at the stage of building design. Its increase is facilitated by a decrease in the number of hinged joints, in some cases the use of integral structural elements, the use of building materials affected by plastic deformation, as well as the identification of building structure elements which under normal operating conditions do not perform bearing functions, but perform them in the case of the local destruction appearance. Scientific novelty. The analyses of the regulatory base and the researchers’ works in a number of countries including Ukraine regarding the progressive destruction is performed. The necessity to improve the concept of designing construction objects is justified. The basis of this concept should consist of both theoretical research and experimental confirmation of the accepted assumptions. Practical value. The necessity of forming a unified approach for determining the problem of survivability and durability of structures, redistribution of loads on undamaged structural elements is substantiated. Directions for the development of measures and design solutions regarding the prevention of the progressive destruction of multi-element bar structures are proposed.

Цель. В данной работе предполагается исследовать влияние условий и параметров микроволнового излучения на изменение физико-механических свойств строительных материалов, в частности оценить стабильность их прочностных характеристик. Методика. Были использованы следующие методы: исследование влияния СВЧ-нагрева на кинетику свойств изделий; определение предела прочности растворов и бетонов на сжатие; сравнительный анализ. В качестве образцов были избраны цементно-песчаные кубики размером 5×5×5 см, изготовленных согласно ДСТУ Б В.2.7-187:2009, с выдержкой для приобретения ими марочной прочности в течение 28 суток. Результаты. Эксперимент заключался в определении влияния мощности СВЧ-излучения и продолжительности его воздействия на изменение прочностных характеристик сухих (естественной влажности) образцов и образцов, насыщенных водой. В ходе эксперимента было проведено испытание на прочность при одноосном сжатии сухих и насыщенных водой образцов, предварительно подвергнутых воздействию СВЧ-излучения (минимальной, средней и максимальной мощности) в диапазоне времени от 1 до 3 мин. Наибольшие разрушающие воздействия СВЧ-излучения на цементно-песчаные образцы достигнуты при значениях мощности от 500 до 900 Вт и продолжительности 2-3 мин. Научная новизна. В данной работе исследовано влияние мощности СВЧ-излучения и продолжительности его воздействия на процесс разрушения цементно-песчаных образцов. Практическая значимость. Установлено, что обработка материалов СВЧ-излучением облегчает процесс их разрушения. Предложенная технология позволит получить научную базу для использования СВЧ-излучения с целью разрушения не только бетона и других строительных материалов, но и горных пород. Также перспективным направлением является изучение обратной задачи-применение СВЧ-излучения при растворении бетонной или другой строительной смеси водой, что в дальнейшем, после ее затвердевания, приведет к повышению прочности изделий. Ключевые слова: СВЧ-излучение; образцы цементно-песчаных кубиков; эксперимент; мощность излучения; прочность; процесс разрушения Наука та прогрес транспорту. Вісник Дніпропетровського національного університету залізничного транспорту, 2019, № 3 (81) ТРАНСПОРТНЕ БУДІВНИЦТВО Creative Commons Attribution 4.

Purpose. There are many problems in the design of anti-landslide constructions, therefore discrete constructions are an alternative to solid anti-landslides. Despite the advantages of such constructions, difficulties also arise when using them. In this work, it is envisaged to develop methods for determining the zone of influence of discrete restraining constructions on the interaction of a sliding soil mass with them and a method for assessing the conditions of a stable state of the soil, which interacts with discrete restraining constructions, by constructing analytical dependencies necessary to determine the zone size and the soil stability coefficient. Methodology. Theoretical studies of geomechanical processes using analytical and numerical mathematical methods, as well as analysis and generalization of theoretical research results were used to achieve the purpose. Findings. The research results presented in the work allow, during the design of landslide discrete constructions, to determine the area of interaction of the shear with discrete retaining constructions, as well as to take into account the stability coefficient of the soil laid between the elements of the discrete retaining structure. Dependences were obtained for determining the zone size in which the sliding soil mass interacts, with discrete retaining constructions, and the soil stability coefficient in the zone of its interaction with these constructions. Originality. Analytical dependencies allow to calculate the boom of lifting the soil dumping arch between the elements of the discrete anti-landslide restraining construction and the coefficient of soil stability. Practical value. The research results allow, when designing discrete restraining constructions, to determine the area of interaction of the shear with these constructions and the stability coefficient of the soil laid between the elements of the discrete restraining construction.

Purpose. The paper analyzes the reasons resulting in destruction of multielement metal structures. Attention is paid to the impact of deformation types on the corrosion of components of such structures as well as to their potential safe operation. Influence of local corrosion in the joints of rod structure members of rod on the terms of its bearing capacity exhaust has been studied. Methodology. To solve the life problem, a 16-rod flat frame has been considered as a simulation structure with design parameters, material characteristics, geometric outline, boundary conditions, and loading conditions. Results. A frame life problem has been considered taking into consideration local corrosion in the joints of rods. The problem involves two calculation schemes with common formulation but having proper peculiarities. Its common is in the availability of inverse association within the calculation models. The difference is as follows. If the number of parameters describing a corrosion process within the frame components is finite during the simulation process in the rod section, where it is fixed, it can be considered as a fragment of flatly stressed plate (FSP) where corrosion velocity depends upon stresses. Since stress-strain state is nonuniform in terms of its area, the number of such parameters tends to infinity. It is the peculiarity defining difference of the research from the majority of the known studies. Scientific novelty. Certain reasons of origination of typical defects and damages of rod metal structures have been considered inclusive of simulation of processes of damage formation as well as defect location. The tendency potential is to expand opportunities while forecasting the structure life with regard to its operational conditions. Practical value. Local corrosion neglecting in the rod joints gives rise to the substantial overestimation of analytical life value. In such a way, structural destruction does not result from bearing capacity exhaust of its component. It results from the broken ties between its separate components despite the fact that a reserve of their bearing capacity is still sufficient.