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Vol. 4 Issue 3

Archives Journal Construction Materials and Products Vol. 4 Issue 3

OBTAINING A THERMAL INSULATION LAYER FROM MONOLITHIC NON-AUTOCLAVED STRUCTURAL AND THERMAL INSULATION FIBRE FOAM CONCRETE

https://doi.org/10.34031/2618-7183-2021-4-3-5-22
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 5-22 p.
Abstract
The possibility of obtaining structural and thermal insulation foam concrete of non-autoclave hardening with improved construction and technical characteristics for the device of a thermal insulation layer in the con-struction of road pavement due to three-dimensional dispersed reinforcement with polypropylene fiber is theoretically justified and experimentally confirmed. Based on the results of studies of the influence of technological factors on the properties of foam concrete, the optimal content (up to 0.25% of the cement mass) and the length (12 mm) of reinforcing polypropylene fibers have been established, which allows obtaining high strength indicators of dispersed-reinforced cement stone for bending (an increase of 12-20%) and compression (an increase of 6-12%) compared with non-reinforced cement stone of non-autoclaved foam concrete. The analysis of the process of structure formation of dispersed reinforced foam concrete from the standpoint of a systematic approach based on multifactorial polynomial models of the influence of the ratio of filler and binder, as well as the number of dispersed reinforcing fibers, which is determined by the optimal conditions for the distribution of solid and gas phases, as well as the reinforcement of adjacent interstitial partitions of foam concrete, linking them into one asociate, which ensures the joint work of the material under various external influences. A method was developed to increase the durability of the road surface and eliminate the influence of the frost heaving effect on the quality of the road surface by introducing the necessary amount of effective thermal insulation layer into the road surface design. The analysis of the regularity of the heat transfer process in the soil mass of the roadbed and multilayer road pavement is carried out. Based on the analysis, the values of the necessary resistance to heat transfer of road pavement for the natural and climatic regions of the country are determined and a method for calculating the value of the thermal insulation (frost-proof) layer of road pavement is proposed. A method was developed for calculating the value of the thermal insulation layer using monolithic fibre foam concrete and a nomogram to determine the required value of the thermal insulation layer made of monolithic non-autoclaved structural and thermal insulation fibre foam concrete of classes D600-D1000.
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EXERGETIC ANALYSIS OF A BUILDING AS A KEY ELEMENT OF A HEAT SUPPLY SYSTEM

https://doi.org/10.34031/2618-7183-2021-4-3-23-40
 23-40 p.
Abstract
The study of the complex influence of weather and climatic factors and their variability on the needs of energy and exergy when creating thermal comfort in a house with various engineering and architectural characteristics is carried out. It is confirmed that even for houses with relatively low thermal characteristics built in accordance with regulatory documents, the role of solar radiation in the formation of the heat balance, especially at the beginning and end of the heating season, is important. Studies showed that due to the combined influence of external meteorological factors, with the improvement of the thermal characteristics of houses, the correlation between the energy demand for creating a favorable microclimate and the outdoor air temperature significantly worsens. It is determined that in this case, the value of the approximation reliability decreases from 1 (with a linear dependence) to 0.55 and lower (with the maximum possible improved thermal characteristics of the house today). This position significantly corrects the operating modes and characteristics of the ST. In particular, this makes it necessary to improve the automatic control system of ST. And this, in turn, increases the investment component of the system. A method was developed for calculating exergy needs to create thermal comfort inside the house by taking into account, using the probability theory, the influence of the random nature of meteorological factors within the heating period, on the basis of which, in the conditions of the region, it is shown and calculated that when de-termining the seasonal exergy needs for the heat supply of the house, the use of a stationary approach leads to an underestimation of the results by 12...28% compared to the dynamic approach.
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IMPROVING THE CALCULATION OF FLEXIBLE CFST-COLUMNS, TAKING INTO ACCOUNT STRESSES IN THE SECTION PLANES

https://doi.org/10.34031/2618-7183-2021-4-3-41-53
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 41-53 p.
Abstract
The article is devoted to a newly developed complex finite element that allows modeling concrete-filled steel tubular columns taking into account the compression of the concrete core from the steel tube, as well as geometric nonlinearity. The derivation of the resolving equations, as well as expressions for the elements of the stiffness matrix, is based on the hypothesis of plane sections. The complex testing of the finite element was performed using the program code written by the authors in the MATLAB language and the ANSYS software, as well as the analysis of the effectiveness of the new FE in comparison with the classical methods of modeling CFST-columns in modern software systems. A significant decrease in the order of the system of FEM equations is demonstrated in comparison with the modeling of CFST-structures in a volumetric formulation in existing design complexes using SOLID elements for a concrete core with 3 degrees of freedom in each of the nodes, and SHELL elements for a steel tube with 6 degrees of freedom in each of the nodes, with a comparable accuracy in determining the stress-strain state. The behavior of steel and concrete in the presented work is assumed to be linearly elastic, however, the described calculation method can be generalized to the case of using nonlinear deformation models of materials.
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MODIFIED CAM-CLAY MODELS FOR DYNAMIC ANALYSIS OF GRANULAR METAMATERIALS IN EARTHQUAKE ENGINEERING

https://doi.org/10.34031/2618-7183-2021-4-3-54-60
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 54-60 p.
Abstract
the problem of protecting buildings and structures from vibrations of natural and artificial nature is important for modern construction. One of such modern methods of protection is seismic pads. The purpose of this work was to study the effect of adding a layer of granular metamaterial under a slab foundation on the vibration of a building under the influence of seismic shear waves (S-waves). To achieve this objective, the finite element method (FEM) was used in combination with Cam-Clay models. The FE model consists of a ten-story superstructure rested on the slab foundation, under which there is a layer of granular metamaterials. 16 models were created taking into account changes in the values of these parameters (pad thickness; density; cohesion; critical state strength parameter (M); Young's modulus-Poisson's ratio). The dynamic analysis performed using the software package Abaqus/CAE showed the effectiveness of granular metamaterials in their ability to dissipate seismic energy and significantly reduce vibration transmitted from the ground to the building.
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