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4. STRUCTURAL DESIGN OF LVL STRUCTURES
The effective contact area perpendicular to the grain,
A
ef
,
should be determined taking into account an effective contact
length parallel to the grain, where the actual contact length,
l
,
at each side is increased.
Eurocode 5 does not include the parameters
k
c,90
and
A
ef
for LVL in different orientations. The value of
k
c,90
should be
taken as 1,0 for LVL in the edgewise loading direction. For LVL
in the flatwise loading direction,
k
c,90
= 1,4 maybe used, when
the distance
ℓ
1
≥ 2h
15
. The contact length and width may be
increased according to the Table 4.7, but not more than
a
,
ℓ
or
ℓ
1
/2, see Figure 4.11. LVL suppliers also have their own tailored
instructions that may give more favourable design results.
The increased contact length and factor
k
c,90
are less fa-
vourable for LVL in edgewise direction, than in the flatwise di-
rection or compared to other wood products have, due to the
failure behaviour of the products. LVL in the flatwise direction,
solid wood and glulam have ductile behaviour under compres-
sion perpendicular to the grain. LVL has high strength values
in the edgewise direction
f
c,90,edge,k
= 6–9 N/mm
2
. However, it
breaks in a more brittle manner, see Figure 4.13. Figure 4.14
shows a calculation example for an LVL beam supported on
an LVL sole plate.
Figure 4.12.
(a) Compression
F
c,90
of a sole plate (b) Compression
F
c,90
of beam on supports (EC5 Figure 6.2).
Table 4.7.
k
c,90
-values and increase of the actual contact length for the design of compression strength perpendicular to the grain of LVL
15
.
1
1
1
Figure 4.13.
Example of LVL-C specimens in compression perpendicular to grain testing. In the flatwise direction LVL-C exhibits a ductile
behaviour. In the edgewise direction orientation LVL-C is much stronger and stiffer, but undergoes more brittle failure due to buckling of the
veneers.
LVL 04, Table 4.7
Loading direction
k
c,90
-values Increase of the actual contact length
a
[mm]
Edgewise compression strength
f
c,90,edge,k
1,0
15
Flatwise compression strength
f
c,90,flat,k
1,4
— parallel to the grain of the surface veneers
30
— perpendicular to the grain of the surface veneers
15
a
One-sided or two-sided increase of the actual contact length, but not more than a, l or l
1
/2 according to EN 1995-1-1.
0
5
10
15
20
25
30
35
40
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
Load F [kN]
Deformation [mm]
Compression perpendicular to grain testing of
LVL-C in edgewise and flatwise directions
LVL-C edgewise
LVL-C flatwise
124
LVL Handbook Europe