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5. STRUCTURAL DESIGN OF CONNECTIONS
The following information should be taken from the nail sup-
plier’s DoP:
• Characteristic yield moment
M
y,k
[Nmm]
• Characteristic withdrawal parameter
f
ax,k
[N/mm
2
]
• Characteristic head out-through parameter
f
head,k
[N/mm
2
]
• Characteristic tensile capacity ftens,k [kN]
• Nail diameter [mm]
• Nail head area [mm
2
]
• Nail length [mm]
• For threaded nails also length of threaded part (
l
g
) and length
of point (
l
p
)
5.5 SCREWED CONNECTIONS
Design instructions for screwed connections are given in Eu-
rocode 5, Section 8.7. The definitions provided in the current
section introduce some differences to the Eurocode 5 instruc-
tions in order to improve the connection design of LVL. Screw
suppliers also have their own design instructions for their fas-
teners documented in their ETAs and DoPs. These must be
treated as separate supplier-specific instructions unless they
make direct reference to Eurocode design.
The following information should be taken from the screw
supplier’s DoP:
• Characteristic yield moment
M
y,k
[Nmm]
• Characteristic withdrawal parameter
f
ax,k
[N/mm
2
]
• Characteristic head out-through parameter
f
head,k
[N/mm
2
]
• Characteristic tensile capacity
f
tens,k
[kN]
• Screw outer thread diameter
d
[mm]
• Screw inner thread diameter
d
1
[mm]
• Screw head diameter
d
h
[mm]
• Screw length
L
[mm]
• Thread length
L
G
[mm]
5.5.1 Laterally loaded screws in LVL
The instructions specific to LVL presented in this subsection
are based on the document
Design rules for LVL to Eurocode 5,
Proposal for discussion in CEN/TC250/SC5
, Prof. Dr.-Ing. H.J.
Blaβ and Dr. –Ing.M.Flaig, Blaβ & Eberhart GmbH, 30.6.2017,
CEN/TC250/SC5/N0764
32
and differ partially from EN1995-
1-1:2004. The effect of the threaded part of the screw shall be
taken into account in determining the load carrying capacity
by using the yield moment capacity of the screw determined in
accordance with EN 14592. The outer thread diameter d shall
be used to determine the embedment strength, the spacing,
edge and end distances and the effective number of screws.
Note: In EN 1995-1-1:2004 the embedment strength is defined
based on an effective diameter def instead of the outer thread
diameter d.
For smooth shank screws, the yield moment capacity of the
smooth shank may be used for plastic hinges occurring within
the length of the smooth shank. Unless a detailed analysis is
made, the yield moment capacity of the smooth shank may be
used, if the smooth shank penetrates into the member contain-
ing the point of the screw by not less than 4
d
.
Unless otherwise stated in this section, the rules for bolts
apply to screws with an outer thread diameter
d
> 12 mm in
predrilled LVL / GLVL members. The embedding strength
f
h,k
should be taken as:
f_(h,k)=(0,082 ∙ (1 - 0,01d) ρ_k)/((k_(90 )∙ sin^2 α + cos^2 α)
∙ (k_(C ) 〖∙ cos〗^2 β 〖+ sin〗^2 β) ∙ (2,5 ∙ cos^2 ε + sin^2 ε) )
(5.22)
where
d
is the outer thread diameter of the screw [mm];
ρ
k
is the characteristic density [kg/m³];
α
is the angle between load and grain direction, see
Figure 5.7; for softwood LVL-C / GLVL-C and α > 45°,
α may be assumed as 45°;
β
is the angle between screw axis and wide face, see
Figure 5.7;
ε
is the angle between screw axis and grain direction,
see Figure 5.7;
k
90
is 1,15 + 0,015 for softwood LVL / GLVL; and
(5.23)
k_C=max{█(d/((d-2) )@1,15) for softwood LVL┤
(5.24)
Unless otherwise stated in this section, the rules for nails apply
to screws with a diameter d ≤ 12 mm or screws in non-pre-
drilled timber or LVL / GLVL members. The embedding
strength should be taken as:
• without predrilled holes in softwood LVL or GLVL
f_(h,k)=(0,082 ∙ ρ_(k ∙)∙ d^(-0,3))/((k_C 〖 ∙
β)
(5.25)
• with predrilled holes in softwood LVL or GLVL
f_(h,k)=(0,082 ∙ (1 - 0,01d) ρ_k)/((k_(C ) 〖
(5.26)
where
k_C={█(1 for LVL-P and GLVL-
2) )@3) for LVL-C and GLVL-C┤ )┤
(5.27)
h,k
=
0,082 ∙ (1 − 0,01 )
k
(
90
∙ sin
2
+ cos
2
) ∙ (
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
)
N/mm
2
C
= max �
( −2)
1,15 for softwood LVL
h,k
=
0,082 ∙
k ∙
∙
−0,3
(
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
)
N/mm
2
h,k
=
0,082 ∙ (1 − 0,01 )
k
(
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
)
N/mm
2
C
= � 1 for LVL − P and GLVL − P
min �
( −2)
3 or LVL − C and GLVL − C
ax,ε,Rk
=
ef
∙
ax
∙
ax,90,k
∙ ∙
ef
β
�
k a
�
0,8
0,5∙
C
= max �
( −2)
1,15 for softwood LVL
h,k
=
0,08 ∙
k ∙
∙
−0,3
(
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
)
N/mm
2
h,k
=
0,082 ∙ (1 − 0,01 )
k
(
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
)
N/mm
2
C
= � 1 for LVL − P and GLVL − P
min �
( −2)
3 or LVL − C and GLVL − C
ef
∙
ax
∙
ax,90,k
∙ ∙
ef k
0,8
made, the yield moment capacity of the smooth shank may be us
penetrates into the member containing the point of the screw by n
Unless otherwise stated in this section, the rules for bolts apply to
thread diameter d > 12 mm in predrilled LVL / GLVL members. Th
should be taken as:
h,k
=
0,082 ∙ (1 − 0,01 )
k
(
90
∙ sin
2
+ cos
2
) ∙ (
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
)
N/mm
2
where
d
is the outer thread diameter of the screw [mm];
ρ
k
is the characteristic density [kg/m³];
α
is the angle between load and grain direction, see Fi
C / GLVL-C and α > 45°, α may be assumed as 45°;
β
is the angle between screw axis and wide face, see
ε
is the angle between screw axis and grain direction,
k
90
is 1,15 + 0,015 for softwood LVL / GLVL; and
C
= max {
( −2)
1,15 for softwood LVL
Unless otherwise stat d in this section, the rules for ails apply to
12 mm or screws in non-predrilled timber or LVL / GLVL members
should be taken as:
- without predrilled holes in softwood VL or G VL
h,k
=
0,082 ∙
k ∙
∙
−0,3
(
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
) N/mm
2
- with predrilled holes in softwood LVL or GLVL
h,k
=
0,082 ∙ (1 − 0,01 )
k
C
∙ cos
2
+ sin
2
) ∙ (2,5 ∙ cos
2
+ sin
2
) N/mm
2
r
C
= { 1 for LVL − P and GLVL − P
min {
( −2)
3 or LVL − C and GLVL − C
5.5.2
Axially loaded screws
For connections in softwood timber or LVL/GLVL with
ε
≥ 15° of s
EN 14592 with:
- 6 mm ≤
d
≤ 12 mm
- 0,6 ≤
d
1
/
d
≤ 0,75
where
d
is the outer thread diameter; and
d
1
is the inner thread diameter
the characteristic withdrawal capacity should be taken as
32
:
n
2
2
c
m
for LVL − P and GLVL − P
LVL Handbook Europe
153