Ductility and Brittleness in small clear notched S-P-F beams

Abstract

Because wood has both brittle and ductile behaviors, the impact of stress concentration around notches is difficult to quantify. This research used the bending stiffness to strength ratio as a means of evaluating stress concentrations in the tension and compression faces of small clear spruce-pine-fir beams. The bending strength and stiffness behavior of wood and wood composites is of particular interest in ladder rails, laminated beams, and structural cross laminated timber, and other heavy timber construction. It was found that rectangular notches up to half of the beam depth located on the tension face reduced the bending strength by 10.5%. The drop in in ductility, as measured by MOE/MOR, was significantly higher, up to 52%. Beams loaded with the notch on the compression face had no statistically significant change in MOR; however, ductility dropped by as much as 30%.