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

1. Initial beam trial size:(a)(b)From Table A8.4(a) and Figure A8.2: Try a 900 mm deep beam which has aL/D ratio in the optimum range of 18:1 to 10:1From Table A8.4(b): Optimum beam width for a 900 deep beam is 90mm to200mm.Select a trial beam size based on deflection criteria.∆ τ = ∆ b + ∆ s + ∆ ns .Assume shear and nail slip deflection are 75% of bending deflection.=>∆ τ = 1.75 x ∆ b .For a simply supported beam with a central point load:∆ b= j 2 x PL 3 / 48(EI)x&∆ ~ 1.75 jτ2 x PL 3 / 48(EI)xF = L 3 /48 EI where F = flexibility co-efficient=>∆ = 1.75 x jτ 2 x Px F=>F(max) ≤ ∆τ / 1.75j 2 PTable 1 (a)Load Load Deflection j2 ∆max/(1.75 x j 2 xType (kN) limit (mm)(mm/kN)DL 10.8 30 2 0.79LL 16.2 30 1 1.06WL -33.0 50 1 0.87P)=>select a beam from Appendix Table A8.5 with a maximum beam flexibility of0.82 mm. From Table A8.5, for a 10.8m span, & F = 0.82 mm/kN, gives a 900mm deeptrial box beam with 150 x 35 LVL flanges and 7mm F11 structural plywood webs.Beam CapacitiesBox Beam: 900 mm deep x 150 x 35 LVL Flanges x 7 mm F11 structural plywood webs.Capacities for the various beam actions have been extracted from Table A8.7 and are givenin TABLE 8.2.Moment Capacity -Tension Flange2f' t(EI) xn / E f d= 161 kNmMoment Capacity - Compression Flange2f' c(EI) x / E fd= 242 kNmWeb Shearf' s(EI) x.n.t w / (EQ)x= 59.3 kNWeb Shear at splice (only one web continuous)f' s(EI) xn. n.t w / (EQ)x= 30.7 kNUnit Shear Flow for Nail Connection(EQ) xf / (EI)x= 0.94 x10-3 -1mmTABLE 8.2 : Beam Capacities77