9.4 ROOF PURLIN Single-span purlins of the roof of an unheated (service class 2) portal frame hall are 45x240 LVL 48 P beams. Roof angle is 15°, span length is L = 4000 mm, spacing s = 900 mm and the purlins are perpendicular to the roof plane having a side support line at the middle of the span. Support length is 45mm. Snow load sk is 2,5 kN/ m2 and own weight of the roof structure is 0,30 kN/m2. For simplification there is no wind load in the example. The purlins are connected to the sides of the portal frame beams and they act also as lateral torsional buckling supports. Therefore the purlins have an axial load of Nk = 3 kN mainly from snow load. Service class SC2. Beam properties: Bending strength edgewise fm,0,edge,k = 44 N/mm2 Bending strength flatwise fm,0,flat,k = 48 N/mm2 Shear strength edgewise fv,0,edge,k = 4,2 N/mm2 Compression parallel to grain fc,0,SC2,k = 29 N/mm2 Compression perpendicular to grain edgewise fc,90,edge,k = 6 N/mm2 Modulus of elasticity E0,k = 11 600 N/mm2 Modulus of elasticity E0,mean = 13 800 N/mm2 Modulus of rigidity G0,edge,k = 600 N/mm2 Modulus of rigidity G0,edge,mean = 400 N/mm2 Area of cross section A = b∙h = 10800 mm2 Section modulus Wy = b∙h2/6 = 4,32∙105 mm3 Section modulus Wz = h∙b2/6 = 8,10∙104 mm3 Moment of inertia Iy = b∙h3/12 = 5,18∙107 mm4 Moment of inertia Iz = h∙b3/12 = 1,82∙106 mm4 Torsion moment of inertia Itor = 0,3∙h∙b3 = 6,56∙106 mm4 Moment stiffness of the joist EIy = 13800 N/mm2 ∙ 6,56∙106 mm4 = 7,15∙1011 Nmm2 Shear rigidity of the joist GA = 600 N/mm2 ∙ 40800 mm2 = 6,48∙106 N Modification factor kmod for medium-term, SC2 = 0,8 Modification factor kdef for SC2 = 0,8 Material safety factor γM (default value in EC5) =1,2 Size effect factor kh = (300/240)0,15 = 1,034 9. CALCULATION EXAMPLES OF LVL STRUCTURES LVL Handbook Europe 191
RkJQdWJsaXNoZXIy MjU0MzgwNw==