No 6 (2024)

The pipe-concrete structures stress-strain state and load-bearing capacity abstract theorem are discussed in this article and experimental studies are carried out to confirm them. Pipe concrete structures prototypes were made of high-strength concrete with spiral reinforcement and high-strength longitudinal reinforcement. The developed compressed pipe-concrete structures have increased strength and have high ultimate axial deformations. Significantly greater energy is required compared to traditionally used load-bearing elements to destroy such a structure. This circumstance makes them especially attractive for use in buildings and structures erected in seismically active zones, as well as for unique buildings and structures. The compressed pipe-concrete element design was improved based on the research results. It was possible to significantly increase its strength compared to known analogues due to the high-strength tensile concrete use. Such elements maximum deformation exceeds 1%, which opens up good opportunities for use. The developed structure high strength and ductility indicate that their destruction requires a large energy. It will significantly increase the frames survivability made of using pipe-concrete elements.

The purpose of the work was to study the heat-protective qualities of foam glass crushed stone based on diatomite and cullet and to assess its applicability as part of the roadway in permafrost areas. Experimental definitions of thermal engineering parameters of foam glass crushed stone made of cullet and diatomite, including bulk density, operational density, compressive strength in a cylinder at a given operational density, thermal conductivity, have been carried out. The thermophysical characteristics of backfilling from foam glass crushed stone based on cullet at a 30% degree of compaction have been studied. The values of thermal conductivity of foam glass crushed stone in dry, frozen, and thawed conditions are determined. The experimental data obtained were the basis for computer modeling and calculation of soil temperature fields with a pavement structure in the territory of permafrost distribution (Republic of Sakha, Yakutia). The calculation of the temperature regime change with a forecast for 12 months was carried out. For comparison, the calculation of a similar road structure without a thermal insulation layer, using coarse sand, is presented. The calculation results show the effectiveness of using foam glass rubble filling in the construction of the pavement; it was found that the thermal insulation layer of foam glass rubble prevents the defrosting of a layer of permafrost soils.

A comfortable acoustic environment in residential and public buildings is an important task that can be solved only in a complex of special constructive measures, one of which is to improve the sound insulation of enclosing structures, including floor-to-floor ceilings. The article presents the results of laboratory tests of building materials used as elastic gaskets when installing floating floors. The compositions of floating floors are described, graphs of the frequency dependence of the improvement of shock noise insulation by tested structures, as well as their single-digit characteristics are given.

Thermal insulation materials used in external enclosing structures, depending on their basic properties, design solutions implemented with their help, the quality of their manufacture and installation, and taking into account the peculiarities of the operating mode, can perform their functions with varying efficiency. This can significantly affect the heat consumption of building heating systems. The paper presents the result of an ongoing experiment to assess the energy consumption of buildings depending on the type of structure and characteristics of their external fences. The test results confirmed the existence of a connection between the intense wind impact on the facade of the building, the air permeability of the enclosing structure and its individual constituent layers and the parameters of the air heating system.

The review of existing mathematical models for humidity conditions was carried out. Methods giving an opportunity to calculate moisture transfer in the sorption zone of humidification and in the supersorption zone are described. The features of calculating moisture distribution using the theory of moisture potential are shown. The new discrete-continuous method for calculating the moisture state of a fence is proposed, which makes it possible to determine the unsteady-state moisture regime using an analytical expression without using various numerical methods. Two formulas for a single-layer and a multi-layer building envelope are derived. The formula allows us to determine the distribution of moisture potential in various sections of building envelopes. The effectiveness of the method is proven by comparing the results obtained with calculations using non-stationary and engineering quasi-stationary calculation methods. The humidity regime of a single-layer enclosing structure in the city of Moscow made of aerated concrete blocks, as well as a two-layer enclosing structure with a clay brick base and silicate brick cladding was calculated. It is shown that the calculation results using the proposed method are both quantitatively and qualitatively close to the distribution obtained using the non-stationary calculation method for both single-layer and multi-layer enclosing structures. The method is recommended for use in engineering work, because it gives a possibility to take into account the inertia of moisture in the building envelope.

The quantitative description of the effect of the resulting chemical structures of polyepoxyurethaneisocyanurates on the glass transition temperature T_g was carried out. This is done by selecting copolymer structures whose T_g value is comparable to the calculated one, and the error does not exceed 1.8–2%. The theoretical data were obtained on the basis of calculations of model structures using the “Cascade” computer program (INEOS RAS).

The scientific works of an outstanding scientist, A.M. Ivanov, devoted to the development of new methods for calculating wooden elements taking into account the time – creep factor have so far aroused great interest among modern researchers. The Voronezh Scientific School of Polymer Concrete A.M. Ivanov has substantiated and created universal models called “structural diagrams”, which lay the probabilistic foundations for evaluating the properties of materials, as well as polymer concrete and other composites. The article describes the life path, the formation of scientific activity and teaching of an outstanding scientist, Dr. of Technical Sciences, Professor A.M. Ivanov, a participant in the Great Patriotic War. Grateful students and followers showed that the issues of reinforcement of steel-polymer concrete structures, anchoring of reinforcement in polymer concrete and calculation of joints of prefabricated steel-polymer concrete structures of solid and annular cross-section with various types of reinforcement; the development of a whole range of polymer materials reinforced with fiberglass reinforcement and wood chips is the result of mentoring activities of an outstanding teacher and scientist.

The abstract generalization of the specifics of fatigue degradation of cement composites due to structural and physical heterogeneity, ambiguity of energy and mechanical effects of induced changes, interdependence of impacts and response, etc., is presented, which together do not make it possible to use the methodology and principles of the limit state method for its assessment. A phenomenological approach to the design accounting of fatigue is proposed by introducing a normative classification of the resistance of composites to non-stationary influences. In the experimental part of the work, prismatic samples of two series were tested: concrete and fiber concrete with polypropylene fibers. All tests were carried out in automatic mode according to a specially developed program at the Instron 5989 test complex, in compliance with the constancy of the deformation rate of the samples of 0.04 mm/s. External influences are modeled by 50 load-unloading cycles with an amplitude of η=0.8 and zero asymmetry (ρ=0). Cyclic loading was completed by monotonous compression until complete destruction of the samples. The acceptability of the laws of the kinetic concept of strength and its criterion (failure time) for assessing fatigue durability is experimentally and analytically substantiated. The practical identity of the kinetics of resistance time and significant indicators of operational suitability is confirmed.