4. STRUCTURAL DESIGN OF LVL STRUCTURES 4.3.7 Bending stress at an angle to the grain The bending stresses at an angle α to the grain should satisfy the following expression 32: σ_(m,α,d)≤f_(m,0,d)/(f_(m,0,d)/f_(m (4.15) where σm,α,d is the bending stress at an angle α to the grain When the characteristic bending strength fm,90,k is not declared for the product, it should be assumed that fm,90,k = ft,90,k. In Figure 4.16, the edgewise bending strength values of LVL 48 P and LVL 36 C at different angles are shown as graphics with this assumption. 4.3.8 Tension stress at an angle to the grain The tensile stresses at an angle α to the grain should satisfy the following expression32: σ_(t,α,d)≤f_(t,0,d)/(f_(t,0,d)/f_(t,90,d) 〖 ∙ (4.16) where σt,α,d is the tensile stress at an angle α to the grain In Figure 4.17, graphically illustrates tensile strength values of LVL 48 P and LVL 36 C at different angles. More advanced instructions on determining the effect of an angle to the grain on LVL strength properties may be found in the manufacturers’ technical documentation. Figure 4.15. Angle α between span direction and grain direction of surface veneer. m,α,d ≤ m,0,d m,0,d m,90,d ∙ sin2 + m,0,d v,d ∙ sin ∙ cos + cos2 (4.15) t,α,d ≤ t,0,d t,0,d t,90,d ∙ sin2 + t,0,d v,d ∙ sin ∙ cos + cos2 (4.16) Figure 4.17. Characteristic edgewise tension strength at an angle α to grain. 0 5 10 15 20 25 30 35 0 5 1015202530354045505560657075808590 [N/mm2] Angle αbetween stress and grain [°] Characteristic edgewise tension strength ft,edge,α,k at an angle αto grain LVL 48 P LVL 36 C 0 5 10 15 20 25 30 35 40 45 0 5 1015202530354045505560657075808590 [N/mm2] Angle αbetween stress and grain [°] Characteristic edgewise bending strength fm,edge,α,k at an angle αto grain LVL 48 P LVL 36 C Figure 4.16. Characteristic edgewise bending strength at an angle α to grain. 126 LVL Handbook Europe
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