Investigação experimental física da influência de entalhes na resistência ao cisalhamento de vigas de madeira

Abstract

Wood is currently considered an ecological alternative to materials that cause severe environmental damage, being increasingly used. However, their heterogeneity and anisotropy make its physical and mechanical properties different in all directions, which should be considered in the design. The Brazilian standard, ABNT NBR 7190/97, recommends that the shear strength value should be taken in the direction parallel to the fibers, which may suggest oversizing of the parts. The present work aims to study the perpendicular shear strength to the fibers in notched beams subjected to simple straight bending and verify if the minimum dimensions required by the norm for the execution of notches can be modified. Beams of two species (Eucalyptus saligna and Araucaria angustifolia) with rectilinear and mislabeled notches were bent to flexion. The carved pieces were subjected to shear, including the supports of the already tested beams, to compare the strengths obtained in the two situations. Crackings were observed on the notch corner of the samples as well as a horizontal shear rupture plan, even though the shearing test was carried out in a vertical plan. The results showed a great difference of shear strength between the evaluated species and no difference between the pieces previously submitted to simple flexion.