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

Transformed SectionSince the plywood skins and the timber stringers will generally be of different species it isnecessary to reduce them to a common basis by computing the transformed section. Thisprocedure entails:• transforming the actual stringer widths to an equivalent width of a skin through theratio:stringerMoEskinMoEx stringerwidth• for skins of differing species, performing a similar transformation to the above, onthe skin not initially chosen.Panel Deflection – Section PropertiesTo determine the relevant panel section properties, i.e the neutral axis and the panelflexural rigidity (EI g ) is best done using the tabular layouts shown in TABLE 11.1 and TABLE11.2.MoE AII AIIE yAElementII Ey266(N/mm) (mm ) (N x 10 ) (mm) (N.mm x 10 )Top SkinStringersBottom Skin∑A 11 E= ∑A 11 Ey=TABLE 11.1: Layout to determine neutral axisy=∑ AIIEy∑ A EIIThe EI o values for the top and bottom skins about their own neutral axes is very smallcompared with the other values and can therefore be disregarded without undue effect on theaccuracy of (EI g ).ItemTop SkinStringersBottom SkinA II E6(N x 10 )IoEIod2(N.mm x 10 6 ) (mm)TABLE 11.2: Layout to determine panel flexural rigidity2A IIEd EI(N.mm2 o + A IIEdx 10 6 ) (N.mm2 x 10 6 )∑EI g =2Flexural deflection can be determined from the familiar relationship:∆b45 wL= (11.3)g384 EIwhere w = panel load in kPaL = panel span in mmEI = flexural rigidity of the panel in N-mm2gShear deflection can be determined from the less familiar relationship for uniform or quarterpointloading:∆S 1.8PL=AG(11.4)where P = total load on panel (N)147