Deformation approach to the calculation of shear strength in transverse bending of wooden elements

Introduction. The calculation and design of bending elements taking into account shear (spalling) are urgent tasks in the design of building structures made of wood. The variant of application of the deformation approach to calculate the strength of wooden elements in transverse bending taking into account shear, based on the use of wood deformation diagrams in compression and tension taking into account nonlinear work, is considered.

Materials and methods. The verification of the proposed strength calculation approach was carried out on the basis of our own experimental studies of wooden elements during transverse bending. The criterion for the destruction of an element is the maximum value of the internal force at which the equilibrium conditions of the system of resolving equations are fulfilled, or non-compliance with shear strength conditions in cross-sections along the length of the shear site of the structure, including taking into account the nonlinear work of wood during compression.

Results. The proposed deformation approach makes it possible to obtain the distribution of shear forces in the area of possible shear of the beam fibres at any stage of loading. An analysis of the results of experimental and theoretical studies indicates the possibility of using the proposed approach to test the strength of wooden structures when bending, taking into account shear. Schemes of wood destruction during shear were experimentally established, which consist in shifting the fibres not along the plane in the neutral zone, but along the annual rings of wood. The proposed destruction criterion makes it possible to take into account the possible displacement of wood during transverse bending.

Conclusions. Based on the research, it was concluded that special attention should be paid to the actual shear strength of wood when calculating bent wooden elements, taking into account shear, which in real structures depends on the shear site, taking into account the location of the growth rings in the cross-section of the structure.

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