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A method has been proposed to calculate the composite timber-concrete bending elements taking into consideration the non-linear work of a nail joint and the stretched reinforcement in a slab. An acting building code regulates the structure estimation based on the linear-elastic work while the pattern of the joint's deformation under loading demonstrates a pronounced non-linear character. Estimation formulae do not account for the presence of reinforcement in a concrete slab, which leads to the irrational use of the structure's load-bearing properties. A dependence has been proposed to determine the slip modulus. The determining coefficients are computed based on the rated characteristics given in the acting design standards. An algorithm for calculating the composite timber-concrete bending structures has been given, taking into consideration the deformation diagram of the joint and reinforcement in the stretched zone of a concrete element. It has been established that the normal stresses for the considered variants of timber-concrete beams, determined on the basis of the proposed procedure and the linear-elastic model, differ by 1-8 %. At loads corresponding to plastic deformations, those stresses that were estimated in line with the linear-elastic model prove to be understated. At loads exceeding 0.75 kN/m for the beam with a span of 3 m, and 0.5 kN/m for the beam with a span of 5 m, stresses in the stretched region of a concrete slab exceed the concrete stretching strength while the stresses in a timber beam do not reach the ultimate values. In fact, in this case, the structure's load-bearing capacity is underutilized because the stretching effort in the cross-section with a crack is accepted by the reinforcement. Based on the design features of timber-concrete floors (the thickness of a slab and protective layer), an analysis of the load-bearing capacity considering the reinforcement has been performed. It has been established that the load-bearing capacity of a slab ensures that an estimated bending momentum is tolerated up until the loads that cause the destruction of the timber beam. At the same time, the conditions for the rational operation of compressed concrete and stretched reinforcement are met

The current trend in the construction industry is the development of projects of multi-storey buildings with a hybrid structural system using mainly timber load-bearing elements. The joints of load-bearing elements are criti-cal points of the frame with glued timber structures in terms of ensuring the load-bearing capacity and servicea-bility of the entire system. Existing publications in this area are mainly aimed at theoretical and experimental as-sessment of the stress-strain state of joints, while information on the construction of components for multi-storey buildings and recommendations for their design is extremely insufficient. The article presents structural solutions of the joints of glued laminated timber columns and beams, namely, hinged, which takes and transmits to the col-umn the support reaction of the beam, and rigid, which in addition to the support reaction takes the bending mo-ment. The support reaction from the beam to the column is transferred through a bolted connection and a T-shaped welded metal element. The bending moment is taken by two angles, which are fixed to the beam and welded to a vertical plate. Criteria of conformity of the proposed joints to load-bearing capacity requirements are pro-posed. The load-bearing capacity of the joint under the action of the support shear force is determined by the shear strength of the bolts in the column; the embedment strength of the metal of the T-shaped plate in the hole and bearing capacity of the bolted connection in the timber element. The action of the support bending moment requires the strength of the angles fastening to the beam and wood in the area of the bolts installation. A detailed algorithm for calculating the proposed design solutions in accordance with the requirements of the design stand-ards has been developed. Keywords: joint, glued laminated timber, beam, column, bearing capacity.

The paper presents an adapted methodology of laser holographic interferometry for an investigation of the stress-strain state of nailed timber connections. During the study the possibility of detecting local deformations in the connection were verified. The optimum conditions for fixing the samples and the loading ranges to ensure an optimal interference pattern were determined. An investigation of the peculiarities of the interaction between the elements and the stress-strain behavior of nailed timber connections was performed. The experimental data obtained on the stress-strain behavior of a nailed timber connection using the laser holographic interferometry method have sufficient repeatability between different series and can also be used as a criterion verification for a finite-element model.