4. STRUCTURAL DESIGN OF LVL STRUCTURES 4.3 LVL DESIGN ACCORDING TO EUROCODE 5 In EN 1995-1-1 (Eurocode 5) the structural design calculations are made in the ultimate limit state (ULS) for bending moment, shear, tension and compression resistance, stability, connections, and stress concentrations in notches, holes and tapered beams. Serviceability limit state (SLS) design calculations are made for deformations and floor vibrations. The following subsections provide instructions on these design calculations with remarks regarding LVL-specific properties. The equations in this Section have individual numbers and when an equation is in the same form in Eurocode 5, it is marked with EC5 and the equation reference number there, e.g., (EC5 6.11). 4.3.1 Bending The following expressions shall be satisfied: σ_(m,y,d)/f_(m,y,d) +k_m (4.4) (EC5 6.11) k_m σ_(m,y,d)/f_(m,y,d) +σ_( (4.5) (EC5 6.12) where σm,y,d and σm,z,d are the design bending stresses about the principal axes as shown in Figure 4.3; fm,y,d and fm,z,d are the corresponding design bending strengths. In addition to kmod and γM, for LVL in edgewise bending the design value is dependent on the member height h. That is taken into consideration by factor kh which is defined as k_h=(300/h)^s≤1,1 (4.6) (EC5 3.3) where h is the member height in bending s is the size effect parameter. For LVL-P and LVL-C strength classes it is 0,15, but manufacturer-defined values are also possible Note: Multiple-glued GLVL products are subject to manufacturer-specific rules for size effect in flatwise bending in flatwise bending (reference size and size effect parameter sflat,m). The value of the factor km should be taken as follows LVL: for rectangular sections: km = 0,7 for other cross sections: km = 1,0 Note: The factor km makes allowance for re-distribution of stresses and the effect of inhomogeneities of the material in the cross-section. Figure 4.3. Member axes of LVL. X is in the grain direction of the surface veneers, Z is in the edgewise direction and Y in the flatwise direction. Figure 4.4. Edgewise and flatwise bending orientations of LVL. Due to the cross veneers, LVL-C panels have a bending strength flatwise perpendicular to the grain fm,90,flat,k that is about 20% of the value along the grain. In the edgewise direction, fm,90,edge,k, the strength is not defined in the DoPs of the product, but it may be calculated using the instructions provided with manufacturer’s technical information. Bending strength fm,90,flat,k and fm,90,edge,k of LVL-P are negligible and cannot be utilized in structural design. m,y,d m,y,d + m m,z,d m,z,d ≤1 (4.4) (EC5 6.11) m m,y,d m,y,d + m,z,d m,z,d ≤1 (4.5) (EC5 6.12) h =�3 ℎ 00� ≤1,1 (4.6) (EC5 3.3) d ≤ v, d m m,y,d m,y,d + m,z,d m,z,d ≤1 (4.5) (EC5 6.12) h =�3 ℎ 00� ≤1,1 (4.6) (EC5 3.3) 120 LVL Handbook Europe
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