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4. STRUCTURAL DESIGN OF LVL STRUCTURES
4.3 LVL DESIGN ACCORDING TO
EUROCODE 5
In EN 1995-1-1 (Eurocode 5) the structural design calculations
are made in the ultimate limit state (ULS) for bending moment,
shear, tension and compression resistance, stability, connec-
tions, and stress concentrations in notches, holes and tapered
beams. Serviceability limit state (SLS) design calculations are
made for deformations and floor vibrations. The following sub-
sections provide instructions on these design calculations with
remarks regarding LVL-specific properties. The equations in
this Section have individual numbers and when an equation is
in the same form in Eurocode 5, it is marked with EC5 and the
equation reference number there, e.g., (EC5 6.11).
4.3.1 Bending
The following expressions shall be satisfied:
σ_(m,y,d)/f_(m,y,d) +k_m
(4.4) (EC5 6.11)
k_m σ_(m,y,d)/f_(m,y,d) +σ_(
(4.5) (EC5 6.12)
where
σ
m,y,d
and
σ
m,z,d
are the design bending stresses about the
principal axes as shown in Figure 4.2;
f
m,y,d
and
f
m,z,d
are the corresponding design bending
strengths. In addition to kmod and γM, for
LVL in edgewise bending the design value
is dependent on the member height h. That
is taken into consideration by factor
k
h
which is defined as
k_h=(300/h)^s≤1,1
(4.6) (EC5 3.3)
where
h
is the member height in bending
s
is the size effect parameter. For LVL-P and LVL-C strength
classes it is 0,15, but manufacturer-defined values are
also possible
Note: Multiple-glued GLVL products are subject to manufac-
turer-specific rules for size effect in flatwise bending in flatwise
bending (reference size and size effect parameter s
flat,m
).
The value of the factor km should be taken as follows LVL:
for rectangular sections:
k
m
= 0,7
for other cross sections:
k
m
= 1,0
Note: The factor k
m
makes allowance for re-distribution of
stresses and the effect of inhomogeneities of the material in the
cross-section.
Figure 4.3.
Member axes of LVL. X is in the grain direction of the
surface veneers, Z is in the edgewise direction and Y in the flatwise
direction.
Figure 4.4.
Edgewise and flatwise bending orientations of LVL.
Due to the cross veneers, LVL-C panels have a bending strength
flatwise perpendicular to the grain
f
m,90,flat,k
that is about 20% of
the value along the grain. In the edgewise direction,
f
m,90,edge,k
,
the strength is not defined in the DoPs of the product, but it
may be calculated using the instructions provided with man-
ufacturer’s technical information. Bending strength
f
m,90,flat,k
and
f
m,90,edge,k
of LVL-P are negligible and cannot be utilized
in structural design.
m,y,d m,y,d
+
m
m,z,d m,z,d
≤ 1
(4.4) (EC5 6.11)
m
m,y,d m,y,d
+
m,z,d m,z,d
≤ 1
(4.5) (EC5 6.12)
h
= �
300 ℎ
� ≤ 1,1
(4.6) (EC5 3.3)
m
m,y,d m,y,d
+
m,z,d m,z,d
≤ 1
(4.5) (EC5 6.12)
h
= �
300 ℎ
� ≤ 1,1
(4.6) (EC5 3.3)
120
LVL Handbook Europe