CIVL439/WO0D476 Consequences of different design values shear Brittle failure .Makefmhof wd of wood ·ecompre-aon Effect of density Grading of timber 860oe49 037-04 0.37043 Defects that affect the strength Variability of material prope 二色三 部普浮名画昌 18 CIVL439/WOOD476 18 Consequences of different design values • Avoid tension perpendicular and shear stresses at all cost • Make use of compression strength of wood as much as possible • Simplify connections and use compression load transfer when possible • Avoid stress concentrations and complex stress patterns Brittle failure of wood Tension perpendicular to grain Tension parallel to grain Shear Effect of density 200 150 MPa) Modulus of rupture Modulus of elasticity Density values: Douglas fir 0.49 Pine 0.37-0.44 Hemlock 0.43 Spruce 0.37-0.43 0 0.4 0.2 1.0 100 0 Strength (M 0.6 Relative density 0.8 50 Compression perpendicular Compression parallel Grading of timber Def h ff ects that affect the strength Design values for structural joists and planks (MPa) Variability of material properties Bridging (load sharing) Selection of members for specific applications Closely spaced members (load sharing) p pp (grading)