2001 ASD Supplements - unprotected PDF - American Wood Council

L-68 APPENDIXC r: 1.15 (repetitive member factor)F b′: 900 psiF v′: 180 psiE: 1,600,000 psiA: 8.25 in. 2S: 7.56 in. 3I: 20.80 in. 4Moment CapacityCM′ r= FCCS ′b F r== 10,172lb.-in.( 900)( 1.3)( 1.15)( 7.56)Shear Capacity2V′ = F′vA ⎛ ⎜ ⎞3⎟⎝ ⎠⎛2⎞= ( 180)( 8.25)⎜ 3⎟⎝ ⎠= 990 lb.Flexural StiffnessEI = (1,600,000)(20.80) = 33 x 10 6 lb.-in. 2Beam Capacity TablesTabulated design values for beams are selected fromTable 4D of NDS Supplement.The general design equation for flexural bending is:M¢³MThe general design equation for flexural shear is:V ¢³ VwhereExample 5:V = shear force due to design loadsV′ = allowable shear capacitySpecies: Douglas Fir-LarchApplication — BeamSize: 6 x 12 (5.5 in. by 11.5 in.)Grade: No. 2F b′: 875 psiF v′: 170 psiE: 1,300,000 psiA: 63.25 in. 2S: 121.23 in. 3I: 697.07 in. 4Moment CapacityM′ = F′Sb= ( 875)( 121.23 )= 106, 076 lb.-in.Shear Capacity2V′ = F′vA ⎛ ⎜ ⎞3⎟⎝ ⎠⎛2⎞= ( 170)( 63.25)⎜ 3⎟⎝ ⎠= 7,168lb.Flexural Stiffnesswhere:M = moment due to design loadsM′ = allowable moment capacityEI = (1,300,000)(697.07) = 906 x 10 6 lb.-in. 2AMERICAN WOOD COUNCIL