2013-4-19 3.Bending members 3.Bending members (3)Shear failure (3)Shear failure 。One of the ven operties of wood （收缩裂缝)oc cur at the whereshear force,without consideration within h 5- ulus transfer of loads in the -mo ent of inertia e oe b e strength parallel to grain critical section 3.Bending members 3.Bending members (④)Notch failure 11111111111111111 盖) where—dept -net depth of the section not including the notch depth 3.Bending members 园 3.Bending members (⑤)Bearing failure notch The"soft"property of wood Ofen govems tension of the fibersa 62013-4-19 6 3. Bending members (3) Shear failure One of the very weak properties of wood Shrinkage cracks （收缩裂缝） often occur at the ends of beams in the zone of maximum shear stress Direct compression transfer of loads in the end zones reduces the total shear force to be carried. 45o critical section This part of the load transferred in direct compression 3. Bending members (3) Shear failure where —— shear force, without consideration within h —— area modulus —— moment of inertia —— width —— shear resistance strength parallel to grain f v Ib VS  V S I b fv 3. Bending members (4) Notch failure where —— depth —— net depth of the section not including the notch depth v n n f h h bh V          2 3 h hn 3. Bending members 3. Bending members (5) Bearing failure The “soft” property of wood Often governs Not only compression perpendicular to grain but also tension of the fibers along edges compression perpendicular to grain tension of fibres along the edges 3. Bending members bearing plate notch