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The purpose of this work is to study the strength of wooden beam structures with local modification of wood in the compressed zone. To achieve this goal, the physical and mechanical characteristics of modified wood were determined using modifiers based on ed-20 epoxy-diane resin, urea-formaldehyde resin, and dimethacrylic polyester. The best physical and mechanical characteristics were obtained for samples using dimethacrylic polyester: the ultimate strength was 84 MPa, the elastic modulus was 21 GPa. The increase in strength compared to solid wood was 46%, and the increase in the modulus of elasticity was 54%. Tests of beam structures with a span of 4.5 m and a cross section of 100×200 mm with local modification of wood in the compressed zone with a polymer composition based on dimethacrylic polyester were carried out. The increase in the strength of beams with local modification in the compressed zone compared to solid wood was 11% within the design loads, and the increase in stiffness by 18%. The “load-strain” relationships are constructed based on the test results. It is established that the greatest effect can be achieved when using external reinforcement systems together in a stretched zone by reducing the influence of defects and defects in beam structures and local modification of the extremely stressed compressed zone.

The stress-strain state of wood-composite beams was studied numerically. Numerical studies were performed on wood-composite floor beams with a cross-section size of 100×240 mm and a length of 4.8 m. it was Experimentally proved that the deformability of wood-glued beams is reduced by 1.8…2.1 times, compared to conventional wooden beams. For wooden beams in the elastic design stage, the limiter is the calculation of the 2nd group of limit States (for stiffness), for composite beams, the calculation of the 1st group of limit States (for strength. The calculation proved that the deformability of wood composite beams is reduced by 1.8…2.1 times, compared to conventional wooden beams. The high efficiency of the finite element method calculation for evaluating the criteria of load-bearing capacity of wood-composite beams up to their destruction is proved.

The problems of calculating deformability composite beams in the software package Lira 9.2 based on real wood work under load are considered. The calculation in the nonlinear formulation using the well-known Belyankin - Prager chart is performed.