Determination of Local Stresses in Places Where the Stiffness of Reinforced Wooden Beams Changes

The problem of local stresses arising in the wood of reinforced beams in the process of loading structures is considered. The calculation of local stresses arising in places of change in the stiffness of reinforced beams should be carried out according to three expressions, taking into account the main factors affecting the stress state of the point of the section under consideration: the placement of reinforcement in the cross section from the breakage of the reinforcement, the action of a uniformly distributed load and support reactions. An analysis of these stresses shows that their development is significantly affected by the intensity of the normal stresses of the reinforcement that occurs in the process of loading the beams. The obtained solution shows that the section height has the greatest influence on the strength and stiffness of reinforced beams. An increase in the height of the section leads to a decrease in the clip effect, i.e. reducing the influence of reinforced zones on each other. At the same time, the uneven distribution of shear stresses along the section height increases, which leads to premature destruction of structures of variable stiffness in the zone of tensile reinforcement breakage. A further direction of research is indicated, which consists in determining the influence of other factors on the strength and stiffness of reinforced beams: the distribution of reinforcement over the section width, the compliance of the steel-wood adhesive joint, the difference in the moduli of elasticity of wood in compression and tension, etc. Their influence can be established by a predictive method for calculating the strength and stiffness of reinforced beams, based on rational planning of the experiment.