2012 ASD/LRFD Manual for Engineered Wood Construction

22 M5: STRUCTURAL GLUED LAMINATED TIMBERM5.4 Special Design ConsiderationsGeneralThis section contains information concerning physicalproperties of structural glued laminated timber membersincluding specific gravity and response to moisture ortemperature.In addition to designing to accommodate dimensionalchanges and detailing for durability, another significantdesign consideration is that of fire performance, which isdiscussed in Chapter M16.Note that the information contained in this sectionaddresses design considerations separate from those describedin NDS 5.4.Specific GravityTable M5.4-1 provides specific gravity values for someof the most common wood species used for structural gluedlaminated timber. These values are used in determiningvarious physical and connection properties. Further, weightfactors are provided at four moisture contents. When thecross-sectional area (in. 2 ) is multiplied by the appropriateweight factor, it provides the weight of the structural gluedlaminated timber member per linear foot of length. Forother moisture contents, the tabulated weight factors canbe interpolated or extrapolated.Structural glued laminated timber members often aremanufactured using different species at different portionsof the cross section. In this case the weight of the structuralglued laminated timber may be computed by the sum ofthe products of the cross-sectional area and the weightfactor for each species.Dimensional ChangesSee M4.4 for information on calculating dimensionalchanges due to moisture or temperature.DurabilitySee M4.4 for information on detailing for durability.Table M5.4-1Average Specific Gravity and Weight FactorWeight Factor 2Species Combination Specific Gravity 1 12% 15% 19% 25%California Redwood (close grain) 0.44 0.195 0.198 0.202 0.208Douglas Fir-Larch 0.50 0.235 0.238 0.242 0.248Douglas Fir (South) 0.46 0.221 0.225 0.229 0.235Eastern Spruce 0.41 0.191 0.194 0.198 0.203Hem-Fir 0.43 0.195 0.198 0.202 0.208Red Maple 0.58 0.261 0.264 0.268 0.274Red Oak 0.67 0.307 0.310 0.314 0.319Southern Pine 0.55 0.252 0.255 0.259 0.265Spruce-Pine-Fir (North) 0.42 0.195 0.198 0.202 0.208Yellow Poplar 0.43 0.213 0.216 0.220 0.2261. Specific gravity is based on weight and volume when ovendry.2. Weight factor shall be multiplied by net cross-sectional area in in. 2 to obtain weight in pounds per lineal foot.AMERICAN WOOD COUNCIL