The actual problem of structural monitoring and modeling of dynamic response from buried building is considered in the framework of arbitrary dynamic load. The results can be used for designing ...underground transport constructions, crossings, buried reservoirs and foundations. In existing methods, the system of sensors that register the response to a dynamic action does not allow for effective interpretation of the signal without understanding the dynamic features and resonance phenomena. The analytical and numerical solution of the problem of the dynamics of a buried object in a layered medium is considered. A multilayer half-space is a set of rigidly interconnected layers characterized by elastic properties. At a distance, an arbitrary dynamic load acts on the half-space, which causes oscillations in the embedded structure, and the sensor system registers the response. The problem of assessing the dynamic stress-strain state (DSSS) is solved using Fourier transforms with the principle of limiting absorption. As an example, the behavior of an embedded massive structure of an underground pedestrian crossing under the influence of a dynamic surface source on a multilayer medium is considered, as well as instrumental support of the sensor system. The solution in the form of stress, strain and displacement fields is obtained and compared with the experimental data. The frequency-dependent characteristics of the system are determined and the possibility of determining the DSSS by a shock pulse is shown.
At present the production of polymer materials is developing intensively, new materials, comparable with steels in their strength properties have recently appeared. In this connection, the analysis ...of polymer materials applied in the pipe industry has been carried out, and the use of ultra-high molecular weight polyethylene (UHMWPE) is proposed as a structural pipeline material, allowing pipes to operate at cryogenic temperatures. The focal point of the article is the consideration of the fracture mechanisms of those materials and the nature of the change in the mechanical properties of UHMWPE under cryogenic temperatures, also taking into account the creep process. The expression for determining the value of the creep modulus depending on the temperature and operating time was obtained. A method is proposed for conducting initial strength estimation. Moreover, the computer model of stress-strain state of an underground cryogenic polymer pipeline for liquefied natural gas transportation is obtained. The results of simulation depict the potential possibility of using of UHMWPE for the cryogenic pipeline construction
Welded rafter trusses are widely used in civil engineering due to the optimal combination of high technological effectiveness and ability to operate under various force scenarios. However nowadays an ...important role in the construction of long-span building structures is played by saving materials, and consumption optimization. This paper reports on the study of 18000 × 3600 mm rectangular welded rafter truss, made of angle profiles with different shelf lengths but the same wall thickness. The method of computer simulation experiment has been applied using ANSYS Workbench 14.5 software package. The scheme of basing, typical for such construction, was accepted: basing on the extreme nodes of the bottom chord and static loading on two intermediate nodes on the top chord. The parameters of the stress-strain state in the structural elements and in places of their connection from the loading start to the onset of the limit state have been identified. It has been found that according to the ratio of material capacity and durability of the structure, the highest indicators are provided by the truss with angle bars of 120x120x10 mm. The research technique accepted in the paper and the obtained results can be used in the design of welded truss construction and in assessing the strength of existing trusses for the purpose of their reconstruction and strengthening.
The assessment of the punching shear capacity for reinforced concrete slabs, carried out according to the regulatorydocuments of a number of countries, leads to significantly various results. At the ...same time, the results of thecalculated forecast may have great differences from the experimental data. A great influence on the accuracy of the resultsof the calculated forecast is exerted by the thickness of the examined slabs, as well as the value of longitudinal reinforcement.These parameters determine the features of the mechanisms of destruction of slabs in case of the punching shearmechanism, as indicated by individual interpretations of the results of experimental studies. In order to determine thefeatures of the punching shear mechanism of reinforced concrete slabs of various thicknesses, numerical studies of theprocess of cracking and destruction of slabs of different thicknesses have been performed. Differences in the mechanismof formation and development of cracks in thin and thick slabs are revealed. The paper shows that the behavior of thinand thick slabs has qualitative distinctions at the initial stages of formation and development of the cracks leading todestruction. The authors have also shown the difference between stress-strain state of thick and thin slabs before destruction.In conclusion, it was established that the influence of longitudinal reinforcement on the strength during punching inthick slabs is much less than in thin ones.When evaluating the punching shear capacity of reinforced concrete slabs, the regulatory documents of different countries give significantly different results. In this case, the calculation results may differ significantly from the experimental data. The deterioration of the thickness of the calculated slabs, as well as the value of the longitudinal reinforcement has a great influence on the accuracy of the calculation results. These parameters determine the features of the destruction mechanisms of slabs under punching. This fact is indicated by some interpretations of the results of experimental studies. In order to establish the peculiarities of the punching shear mechanism of reinforced concrete slabs of different thicknesses, a numerical investigation of the cracking and destruction of slabs of different thicknesses have been performed. Differences in the mechanism of formation and development of cracks in thin and thick slabs have been revealed. The paper shows that the behavior of thin and thick slabs has qualitative differences at the initial stages of the cracks formation and development that leads to destruction. The difference between stress-strain state of thick and thin slabs before breaking have been shown. It was found that the effect of longitudinal reinforcement on the punching shear strength in thick slabs is much less than in thin ones.
In this article the analysis of temperature conditions and stress–strain state during radial-shear rolling (RSR) of bars from industrial deformed aluminum alloys A2024 and A7075 was carried out. The ...RSR was made for four different variants of elongation ratio µ for each alloy: 1.2, 1.6, 2.0, 2.4. It is shown that for the alloy A2024 in the zone of maximum reduction, the growth of elongation ratio leads to the increase in the temperature difference, and for A7075, the temperature difference decreases. After rolling the temperature of bar increases due to the deformation heating in average by 5–30°C in dependence on reduction per pass. At deformation with µ <2.0 the axis zone of bars is characterized by the presence of positive average stresses. The analysis of stress triaxiality parameter showed that the alloy A2024 has a large margin of technological plasticity in comparison with the alloy A7075 when deformed by the RSR method with similar parameter.
A numerical analysis of the reinforcing particle shape and interface strength effects on the deformation and fracture behavior of an Al/Al
2O
3 composite is performed. Three-dimensional calculations ...are carried out for five elastic–brittle particles embedded into the elastic–plastic matrix, the reinforcing particle shape being varied from spherical to strongly irregular. It is shown that microstructural heterogeneity of the composite gives rise to a complex stress–strain state in the vicinity of particle boundaries and hence to near-interface areas undergoing tensile deformation both in tension and compression. Within the strain range under study, compressive strength is not achieved, either in compression or in tension, i.e., all cracks grow only under tensile stress. Particle fracture is found to occur by two mechanisms: interface debonding and particle cracking. Individual and combined effects of the particle shape, interface strength, and loading conditions on the fracture mechanisms are analyzed.
To investigate the fractal dimension and its variation of intact and compacted loess, consolidated-drained (CD) triaxial tests were performed to obtain intact and compacted loess specimens at ...different stress-strain states, their pore-size distribution (PSD) curves were measured by using the mercury intrusion porosimetry (MIP) technique. Based on the PSDs, three models (namely, Menger sponge model, Neimark model and the model based on the law of thermodynamics) were used to determine the fractal dimensions of specimens. The results show that there have 3 or 4 fractal intervals (or fractal dimensions, i.e., Ds1, Ds2, Ds3, Ds4,) when using Menger sponge model, only Ds3 satisfies the definition of fractal dimension. Neimark model can be used to determine the fractal dimensions of inter-aggregate pores and intra-aggregate pores, respectively (i.e., DNmacro and DNmicro). Most DNmacro values are meaningless physically, DNmicro increases with the increase of axial strain during shearing, suggesting that the surfaces of pores become complex with the increase of axial strain. The model based on the law of thermodynamics is the most appropriate if only one fractal dimension (i.e., Df) is expected in the whole measurable range of pore diameter. Df increases linearly with the growth of confining stress during consolidation or axial strain during shearing for both loess soils, indicating that the roughness of the pore surfaces increases with the increase in stress or strain. Besides, the fractal dimensions of intact and compacted loess were compared. According to the variations of PSD and Df, the mechanism for the evolution of the loess soil pore structure is proposed. These findings are expected to provide new insight into establishment of the connection between microstructure and macro stress-strain state of loess.
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•The fractal dimensions of loess specimens were determined using three models.•Variations of the PSD and fractal dimension with stress-strain state were analyzed.•The mechanism for the evolution of the loess soil pore structure is proposed.
Introduction: In recent years, houses out of vertical squared timber have become widespread. Vertical bars make it possible to use the effective wood behavior in compression and ensure maximum ...strength of the material along the fibers. Vertical bars are subject to compression with bending, which can result in loss of strength and buckling in building structures. In the available research papers and technical literature, the issue of the stress-strain state of such walls has not been analyzed. The purpose of this study was to formulate a calculation method for walls out of vertical squared timber, based on the available traditional approaches to wooden structures. We propose a calculation method for walls out of vertical squared timber as a set of elements resisting compression with bending, including a check for limiting slenderness. Results: Permissible heights of walls for buildings with bays of 10 and 12 m were obtained. The results can be used in the design of low-rise residential and public buildings, mansard superstructures of multi-story buildings.
The article presents scientific approaches to the study of the stress-strain state of linearly extended structures containing crimping devices. Examples of such structures include rope systems, ...pipelines for transporting media under pressure. The study of the stress-strain state of a gas pipeline on which a steel coupling used for the repair of substructures is installed is considered in detail.
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