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

Determination of Z is most conveniently done through TABLE 11.5 :Element IoAIId Io + A II d626Top skin 0.34 x 10 11520 77.1 68.5 x 10Stringer650.6 x 10 3402026.4652.0 x 10Bottom skin60.07 x 10 7200285.9653.2 x 10ΣI g =6173.7 x 10TABLE 11.5: Layout to determine the gross second moment of area22Hence I g is:For the top skin:For bottom skin:Ig = 173.7 x 10 6 mm 4 for 1200 wide panelZt I6I g 173.7 x10= = =y 76.2 85.6Z t = 2.03 x 10 6 mm 3φM = (0.72 x 35 x 2.03 x 10 6 )N-mmφM = 51.1 kN-mZ bI 173.7 x106g= =91.3 91.3Z b = 2.02 x 10 6 3mmφM = (0.72 x 35 x 2.02 x 10)N-mmφM = 50.9 kN-mDesign Action EffectTABLE 11.6 gives the relevant loading combinations and the associated duration of load parameter D L whichshows the critical load case.Load CombinationsCalculation+ wL 2Load EffectkM =1(kN/m)8(kNm)=Permanent 1.25G + Ψ c Q (1.25 x 0.5) + (0.4 x 2) = 1.43kPa 1.43 x 1.2 -= 1.72 0.57 5.38 9.43Long term 1.25G + 1.5Q (1.25 x 0.5) + (1.25 x 2) = 3.63kPa 3.63 x 1.2 -= 4.36 0.8 13.63 17TABLE 11.6: Design action effectFor the strength limit state:*D L Mk1D L from TABLE 11.6 shows the worst loading case to result in a moment of 13.63kNm which is much lessthan 30kNm moment capacity for the bottom skin.Splice Plate CheckTension SpliceThe relationship for a splice plate stress check given in Section 11.5 of Design Methodology is:fstfst⎡ 2wL Es Ws ⎤= ⎢6x x y x x10 ⎥MPa⎢ 8 (EIg) Wp⎣⎥⎦⎡ 22 x 1.2 x 5 10500984 ⎤= ⎢6xx 90.4 x x10 ⎥⎢ 810197.4 x10 1200⎣⎥⎦= 2.95MPaIf the splice plate was 17mm F11 structural plywood with its face grain parallel to the direction ofspanning then:f’ t = 20MPa which, without further consideration would therefore obviously be satisfactory.154