4.4.2 Beams and columns When LVL-P or LVL-C members are glued together in the same direction as rectangular GLVL cross sections, the material values of the LVL lamina may be used. Additionally, the size effect shall be taken into account for the shear strength and bending strength flatwise to the LVL lamellas. The size effect parameters are declared in manufacturers’ technical documentation. LVL I-beams and box beams have LVL-P flanges and LVL-C webs which keep the beams straight and stable in changing moisture conditions. Glued thin-webbed I-beam and box beam specific design instructions are given in Eurocode 5 clause 9.1.1. For the flanges it shall be verified that: • Axial tension stress σf,t,max at the extreme fibre of the flange edge does not exceed the bending strength fm,d of the flange material • Axial tension stress σf,t,d at the centre of the flange does not exceed the tension strength ft,0,d of the material • Axial compression stress σf,c,max at the extreme fibre of the flange edge does not exceed the bending strength fm,d of the flange material • Axial compression stress σf,c,d at the centre of the flange does not exceed the compression strength fc,0,d of the material taking into consideration lateral instability For the web material it shall be verified that: • Compressive and tension stresses σw,c,max and σw,t,max do not exceed the respective strengths fw,t,0,d and fw,c,0,d of the web material • Design shear force acting on the web Fv,w,Ed does not exceed the shear capacity Rv,w,d of the beam taking into consideration buckling as a plate 4. STRUCTURAL DESIGN OF LVL STRUCTURES Figure 4.30. Multiple-glued GLVL beams. For glued joints between web(s) and flanges (section 1-1 in Figure 4.31), it should be verified by equation (9.10) of Eurocode 5 that the shear stress τmean,d does not exceed the planar shear strength of the flange or web materials. In SLS design, bending and shear deformations are taken into account. For simplicity, the shear rigidity GA may be evaluated based on the webs only. LVL I-beam and box beam suppliers also have more advanced design instructions tailored and approved for their elements as part of their technical documentation. Figure 4.31. GLVL I-beams, box beams and stress distribution in the cross section. Section 1-1 is glued joint between web and flange. 140 LVL Handbook Europe
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