2001 ASD Supplements - unprotected PDF - American Wood Council

ASD STRUCTURAL GLUED LAMINATED TIMBER SUPPLEMENTGL-113.4 Radial Tension and CompressionWhen a curved member is loaded in bending, radialstresses are induced. When the bending moment is in thedirection that tends to decrease the curvature or increasethe radius, the radial stress is in radial tension, F rt . On theother hand, when the bending moment is in the directionthat tends to increase the curvature or decrease the radius,the radial stress is in radial compression, F rc . Table 3.4provides allowable radial tensile stresses for glued laminatedtimber. These values are subject to adjustments forduration of load and wet conditions of use (16% moisturecontent or higher). If the adjusted value is exceeded, appropriatemechanical reinforcements shall be used to resistall applied radial tensile stresses. The maximum moisturecontent of the laminations shall not exceed 12% at thetime of the reinforcement manufacturing.Table 3.3The allowable radial compressive stress has been traditionallylimited to the design value in compressionperpendicular to grain, F c⊥ , of the grade and species beingused. Also given in Table 3.4 are allowable radial compressivestresses for glued laminated timber. Theseallowable radial compressive stresses are not subject tothe adjustments for the duration of load, but shall be adjustedfor wet conditions of use when appropriate.Allowable Properties and Moduli of Elasticity for Glued LaminatedTimber with Tapered Cuts on Compression FaceStress class(a)F bx , psi F (b) c⊥x , psi(a)E x , 10 6 psi16F-1.3E 1,050 315 1.220F-1.5E 1,250 375 1.424F-1.7E 1,250 375 1.424F-1.8E 2,000 560 1.726F-1.9E 2,000 560 1.728F-2.1E 2,400 650 1.930F-2.1E 2,400 650 1.9aValue is applicable to members that have up to 2/3 the depth on the compression side removed by taper cutting. Value is for dry conditions of use.bDesign value in compression perpendicular to grain for the core laminations of the combination.3ALLOWABLE STRESS AND STIFFNESSTable 3.4Allowable Radial Stresses aaSpecies Radial Tension (F rt ), psi Radial Compression (F rc ),Wind and Earthquake Other Loadings psiAlaska Cedar 63 15 470California Redwood 42 42 315Canadian Spruce Pine 53 15 560Douglas Fir-Larch 55 15 560Douglas Fir-South 55 15 560Eastern Spruce 48 15 300Hem-Fir 52 15 375Softwood Species (WW) 47 15 255Southern Pine 67 67 650The wet use factor, C M , is equal to 0.875 for radial tensile stresses and 0.53 for radial compressive stresses.APA – The Engineered Wood Association