Plywood Design Fundamentals - Canadian Plywood Association

2012_april revised_48945_en_design.qxd 19/04/2012 3:04 PM Page 13
Tension Parallel to Panel Edge
The factored tensile resistance parallel to a panel edge shall
be taken as:
Tr = FTpbn where:
F = 0.95 (for all plywood thicknesses and number of
plies except three and four ply construction
stressed perpendicular to face grain)
F = 0.60 (for three and four ply construction
stressed perpendicular to face grain)
= tp (KD KS KT) Tp tp bn = Specified strength capacity in tension (N/mm)
= Net width of plywood panel after cutting of holes,
etc. (mm).
Compressive Resistance Perpendicular to Face (Bearing)
The factored bearing resistance normal to plane of plies
shall be taken as:
Qr = FQp Ab where:
F = 0.95
Qp = qp (KD KS KT) qp = Specified strength capacity in bearing normal to
plane of panel (MPa)
= Bearing area (mm2 )
A b
4.8 Design Example
Design a heavy industrial floor deck exposed to wet service
conditions. Edge support is to be provided by tongues and
grooves. The live load, dead load and span are known.
Determine the required thickness of EASY T&G Douglas Fir
plywood.
M max
0.1071 wl 2
0.1071 (1.5L + 1.25D)l 2
0.1071 (1.5 x 17 kN/m + 1.25 x 2 kN/m)(0.407 m) 2
m p
V max
0.607 wl
0.607 (1.5L + 1.25D)l
0.607 (1.5 x 17 kN/m + 1.25 x 2 kN/m)(0.407 m)
v pb
Dmax 0.0069 wl 4 /Bbr 0.0069 (L + D)l 4 /FB bb p
0.0069 (L + D)l 4 /Fb p(K S K T)b p
0.607 (17 kN/m + 2 kN/m)(0.407 m) 4 /1.0 b b(0.85 x1.0)(1.0 m)
b b
Bending
Planar Shear Due to Bending
Deflection
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Design assumptions:
Live Load (uniformly distributed over three
or more equal spans, all spans loaded) =17 kPa
Dead Load (uniformly distributed over three
or more equal spans, all spans loaded) =2 kPa
Span (from centre to centre of supports) =407 mm
Maximum deflection of plywood between
supports (D allowable) =l/360
EASY T&G Douglas Fir plywood applied with face grain
across the supports
Wet service conditions:
Bending and Planar Shear K S=0.8
Stiffness =0.85
Standard term duration of loading K D=1.0
No chemical treatments K T=1.0
Strength limit states design load a L =1.50
factors a D =1.25
Serviceability limit states design load a L =1.00
factors a D =1.00
Importance Category =Normal
Design Calculations:
Since loading is uniformly distributed, unit widths are
employed in all calculations:
Specified Live Load (L) = (17kN/m 2 )(1.0m) =17 kN/m
Specified Dead Load (D) = (2 kN/m 2 )(1.0m)=2 kN/m
< M r
< F M p b p
< F m p (K D K S K T)b p
< 0.95m p (1.0 x 0.8 x 1.0) (1.0 m)
> 0.654 kN m/m = 654 N•mm/mm
< V rp
< F V pb b p
< F v pb (K D K S K T)b p
< 0.95v pb (1.0 x 0.8 x 1.0) (1.0 m)
> 9.1 kN/m = 9.1 N/mm
< D allow
< l/360
< l/360
< l/360
< 0.407 m/360
> 3.74 kN m = 3,740,000 N•mm 2 /mm
certiWood Canply plywood Design Fundamentals