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High air permeability and the presence of thermal bridges at the junctions of wooden frame wall panels have a significant impact on the thermal balance of the building and its operational characteristics. The importance of improving the energy efficiency of nodal interfaces of panels with a wooden frame is undeniable. To date, there is no single generally accepted method for calculating heat losses through nodal interfaces of panels with a wooden frame. Based on the analysis carried out, it is necessary to carry out calculations and measurements that allow creating this calculation methodology. To carry out numerical studies, a list of characteristics and parameters affecting their conduct is formulated: the influence of the thickness of a li-ear-discrete inclusion on the heat-protective properties of the panel docking unit; the thermal conductivity characteristics of the material used to fill linear-discrete inclusions affecting the heat flux density of the node interface; consideration of the influence of the outdoor temperature of air depending on different climatic zones on the density of heat flow. The dependences of the heat flux density on the "inner" surface of the experimental samples on the thermal conductivity coefficient of the material of the insulating insert, the width of the insulating insert and the outside air temperature were revealed and the nature of the temperature distribution on the "inner" surface of the prototypes was established. By calculating two-dimensional temperature fields in the cross section of the node, isofields of temperature distribution inside the structure, isofields of heat flux density and its direction, lines of temperature distribution and heat flux density along the inner and outer surfaces are obtained. It was found that the heat flux density in the ribs with heat-insulating inclusions is lower in comparison with solid wood parts by an amount from 13% to 52%.

The lack of a clear regulatory framework governing the use of polymer composites to strengthen wooden structures, stimulates the conduct of numerous studies in this area. An important task is to obtain reinforcing materials with the best physico-mechanical and operational parameters. The choice of the type of curing adhesive has a great influence to characteristics of polymer composites such as viscoelastic parameters of the material, adhesion properties on the contact surfaces, the presence of internal defects, etc. The paper describes a method for determining the physicomechanical characteristics of a composite material based on experimental studies. The stand, test samples and the pattern array of tensometric sensors for testing according to Russian State Standard GOST R 56800-2015 "Polymer composites. Determination of tensile properties of unreinforced and reinforced materials have been presented. Dependences of stress-strain, modulus of elasticity, Poisson's ratio, tensile strength for laminate polymer composite have been obtained. Comparative analysis of the obtained results for various adhesive compositions has been performed. According to the results of experimental studies, it was found that the physicomechanical characteristics of polymer composites based on epoxy matrix are higher than those of polyurethane matrix composites due to uniform filling of the filler volume, as well as better wettability of the reinforcing fibers. In conclusion, the article draws conclusions about the effect of the adhesive composition on the mechanical characteristics of the obtained composites have been made, relevance and applied significance of the investigation for strengthening the compressed-flexural elements of wooden structures has been justified.

Wooden multi-span beams with steel reinforcement were studied experimentally on a stationary stand using an eight-point loading scheme that simulated a load uniformly distributed over the beam span. The studies were carried out on beams with a span of 4.8 m with a cross-sectional area of 40 mm × 80 mm, reinforced in the stretched zones of the cross-section with rods made of hot-rolled steel reinforcement of A400 class. The rational zones for the location of reinforcements in the tensioned and compressed zones of the beams were determined. The rational placements of reinforcement in the support and span zones was based on the numerical simulation of the volumetric stress state calculated using the finite element method. It was experimentally confirmed that the failure of wood composite beams had a plastic nature and occurred only along normal sections. This excluded the possibility of brittle fracture from shear stresses and ensured the operational reliability of structures as a whole. It was shown that the proposed rational reinforcement of wooden beams increased their bearing capacity by 175% and reduced bearing deformability by 85%. The results obtained indicated high efficiency of the application of the developed method of reinforcement in beams of roofs and floors of buildings.