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

5. Check Beam Stiffness:Check beam deflection ∆ is not excessive, where :Box Beam Section Property Formula∆ τ = ∆b + ∆ s + ∆A f = Area of flange = 2 bf t fA w = Area of web = 2 d twA s = Web shear Area = 2 dn t wwhere d n = depth between top and bottom flange-web nailing= (d – t f ), usuallynsPlywood Webbed Beam DimensionsFirst Moment of AreaQ xf= First Moment of Area of the flange about the beam x axis= Afy f = b f t f (d-t f )/2Qxw(EQ) x(EQ) xn= First Moment of Area of the webs about the beam x axis= nk34t w d 2 /8= First Moment of Area of the Box Beam= E f Q xf + E w Q xw= (EQ) x at web butt joint (i.e. only one web continuous, n = 1)Second Moment of AreaI xf = Second Moment of Area of the flange about the beam x-axis= b f (d 3 -d 3 w )/12Ixw= Second Moment of Area of the web about the beam x-axis= nk 34 t w d 3 /12where n = number of plywood webs (e.g. 2 for a box beam)and k 34 = parallel ply factor (note k 34 is not an AS1720.1-1997 factor)Table 8.1I yfIyw= Second Moment of Area of the Flange about the beam y axis= 2t f b f 3 /12= Second Moment of Area of the Web about the beam y axis= k 34 t w d(b f + t w ) 2 /275