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

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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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