Reinforcement Predesign of Composites used to Strengthen Timber Members Loaded in Bending

摘要

Using timber for construction of frame structures is opportune due to low density and good strength properties of wood. The main drawback of wood is given by its reduced modulus of elasticity parallel to grain that negatively affects structural elements stiffness. Consequently, it would be an important achievement to have the possibility to determine the cross-section dimensions of timber frame structural elements from load bearing capacity criteria. The increasing of structural elements stiffness may be achieved by using wood-composite hybrid cross sections in specific “target” locations along timber bars. From the methods that may be used to compose hybrid wood-composite cross-sections of timber bars are chosen, for analysis, multilayered composite strips of matrix-unidirectional fabric type. The attempt to determine a predesign formula for the warp yarns` quality of the reinforcing unidirectional fabric is based on the principles of constituent composite lamella structure and work hypotheses of timber – composite strip hybrid assembly. Accepting that, the tensile strength of the constituent composite lamella is function of only fiber volume fraction and tension strength of reinforcing phase, a simple and efficient criterium is proposed, in order to predesign materials quality used for reinforcement yarns.