Progress in research for Bending
bearring capacity of Ribbed
plywood plates(Wood processing, bearring envelope structures, multistorey hybrid
structures)
Riga Technical University
Institute of Structural Engineering and Reconstruction
10.12.2015
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Actuallity
Layered wooden material with improved wood properties, with
possibility
• to improve strength (improved with reduce of imperfections)
• to obtain higher specific strength
• to obtain low amount of waste
• to vary with required properties in various directions
• to get waved form
• To use waved form in ribbed plates
http://www.finieris.lv/lv/produkti/saplaksnis/riga-ply 2
Plate with Cell Type Core
Advantages
• Technological • Transversal direction• Buckling improvement• Shear properties
3
Cell Type Hollow Rib
Z
Y
X
G. Frolovs
Waved rib
90 / 0 / 90
Waved rib
90 / 0 / 90
Straight rib
0 / n*90/0 / 90/0
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Basic Technological Principles
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Patent No. 14979 P-14-103 „ Method for producing ribbed plates”. K.Rocēns, A.Kukule, Ģ.Frolovs, J.Šliseris Ģ. BērziņšAssigned patent application P-15-108 “Method and equipment of production for ribbed composite plate with goffered wood-based core” K.Rocēns, Ģ. Frolovs, A. Kukule, J. Šliseris.
Basic Technological Principles
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Basic Technological Principles
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0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,03 0,06 0,09 0,12 0,15
Spe
cifi
c b
en
din
g lo
ad b
ear
ing
cap
acit
y [k
N/m
2/k
g)]
Thickness of a plate[m]
Plywood
Only flat ribs
Flat and curved ribs
Only curved ribs
Specific bending bearing capacity (capacity to weight) for different plates
Three types of ribs analyzed:
flat rib; flat and curved rib; only curved rib
Numerical investigations
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Stiffness-to-Mass
difference
Stifn
ess-t
o-w
eig
htra
tio
[kN
m2/k
g]
Longitude bending stiffness-to-weight ratio depending on a thickness of straight rib part and width of a rib. .L=1.5m; Hp=0.3m; Nw=3; thicknesses of other parts: ta=tu=twr=4mm;
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Stiffness-to-Weight difference
Nw 5
4.5
4
3.5
3
0.72
0.7
0.68
0.66
Br
0.140.12
0.10.08
0.06
Cross-section Plane of Response Surface
(Square )
Number of Waves
Stiffness to Weight ratio for cell type hollow ribs comparing to standard plywood
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Narrow Glued Edge-to-Surface Joint
Shear joint specimen with dimensions
Different pressures applied(0.3MPa; 0.5MPa; 1.0 Mpa)
Tension joint specimen with dimensions
Surface-to-Surface
ASTM D2528-96 «Standard Test Method for Strength Properties of Double Lap Shear Adhesive Joints by Tension Loading»
ModifiedEdge-to-Surface
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Narrow Glued Edge-to-Surface Joint
Specimen placed in the testing machine (Instron 3000).
• Various plywood thicknesses and orientations for ribs
• Various material and thicknesses for skins
Ultrasound tests Digital Image Correlation Tests until fracture of a joint
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Shear stresses in edge plywoodand normal stresses in surface plywood
ANSYS simulation (simplified)
Ultimate Strength
Ultimate strength for different levels of pressure for all samples.
Narrow Glued Edge-to-Surface Joint
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Stiffness
Deformations in the middle part of the joint and exactly at joint comparison.
Left Right
Middle
Narrow Glued Edge-to-Surface Joint
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Summary
For ribbed plates
• The influence the shape of ribs on rational geometrical properties of the proposedstructure is obtained in form of polynomial function EI (L,Hp,Br,Nw,Tsr) depending on aheight of plate and influencable form of waves and thickness of waved rib.
• By changing geometry of ribs the stiffness-to-mass ratio increases in average for about50 % (30% Stiffness decrease and 55% mass decrease) comparing to standard plywoodplates.
For glued joints
• If most of the layers of edge elements are in longitudinal direction it is practically enoughwith bond pressure 5 kg/cm2 (70 psi) For cases with more layers of edge elements are intransversal direction it is recommended to increase bond pressure up to 10 kg/cm2 (140psi)
• The results describing stiffness of glued joint showed less influence of bond pressure
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Thank you for attention !
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