EWPAA Structural Plywood and LVL Design Manual - Engineered ...

FIGURE 5.5 shows an I-beam defining the relevant design parameters, with respect to thevalues given in TABLE 5.9, for the edge axial forces, moments and shears.FIGURE 5.5: Defines diaphragm buckling parametersAS1720.1-1997k 19 – Moisture content factorClause 5.3.3The k 19 moisture content factor given in TABLE 5.10, is used to modify plywood strength capacityto allow for the reduction in strength that will result if for a 12 month period the averagemoisture content of the plywood in service remains higher than 15%. Where the averagemoisture content of plywood, over a 12 month period is less than or equal to 15%, k 19 = 1.0.Some examples of where average moisture content may remain above 15% for a 12 monthperiod are applications in continuously humid environments and also where the plywood isconstantly sprayed with water.Factor k19Moisture MoistureStrength PropertyContent* Content*15% or less 25% or moreBending 1.0 0.6Tension in plane of sheet 1.0 0.7Shear 1.0 0.6Compression in plane of sheet 1.0 0.4Compression in normal to plane of sheet 1.0 0.45*For moisture contents between 15 and 25%, use linear interpolation to obtain k 19factorTABLE 5.10: Moisture Content Factor, k19AS1720.1-1997g 19 – Plywood Assembly FactorClause 5.3.5The g 19 factor in TABLE 5.11 and TABLE 5.12, allows for the differing grain orientation of thetimber veneers within the plywood sheet. The g 19 factor affects both strength and stiffnessand varies depending on whether the plywood is loaded in plane or normal to the face.For Plywood Loaded Normal to the Face : The g 19 assembly factor given in TABLE 5.11 is usedto increase the bending strength capacity of three ply plywood when loaded with face grainperpendicular to span and to reduce the shear strength capacity. For all other propertieslisted in TABLE 5.11 g 19 = 1. The g 19 factor applied to the bending strength capacity of plywoodwith 3 veneer layers, loaded perpendicular to span, compensates for the underestimation inthe value of the section modulus for three ply plywood with face grain perpendicular to span,calculated using parallel ply theory. The g 19 factor applied to shear strength accounts for thereduced shear strength capacity of the plywood due to the rolling shear tendency of theplywood cross-bands.31