The object of research is composite structures with semi-rigidity ties, such as ribbed steel-concrete and wood-concrete floors, and structures based on structural wood and wood-composite materials, which are widely used in industrial and civil building. As a rule, various types of mechanical ties are used as shear ties in composite structures. In calculations of such structures according to the classical method, the behaviour of shear ties is generally assumed to be linear-elastic. It does not make it possible to consider the real character of the deformation of the ties during shear force action. Method. The presented calculation algorithm is based on the solution of A.R. Rzhanitsyn for the differential equation for the two-layer composite rod. Separating the element into sections and set the boundary conditions at the borders of the sections, a system of linear equations can be obtained from which the values of the shear forces T and integral constants can be determined. This approach makes it possible to determine forces in the shear ties and normal stresses in the layers in any cross-section of the composite element. As an example, a two-layer composite beam is considered, the layers of which are connected by cylindrical nails, the deformation of which occurs according to non-linear behaviour. Results. it was concluded that the calculation according to the classical method, taking into account linear behaviour of ties, gives an error of up to 25% while the shear force in the ties determining and up to 111% when normal stresses in the layers of the composite beam were determining. Such errors do not make it possible to get a reliable estimation of the strength of materials and shear ties of the composite structure.