Estudo experimental físico 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 mainly due to the professionals' awareness of its constructive potential and its structural and environmental advantages. However, the absence of adequate structural projects and a shortage of skilled labor leads to the need to use scientific studies that make it possible to use wood efficiently and productively. Their heterogeneity and anisotropy make its physical and mechanical properties different in all directions, which should be considered in the design. For safety reasons, the Brazilian standard, ABNT NBR 7190/97, determines that the shear strength value should be taken in the direction parallel to the fibers, which may lead to 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 updated. Wood 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 rupture 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.