LVL Handbook EUROPE

5. STRUCTURAL DESIGN OF CONNECTIONS

Connection detailing

Members should be pre-drilled when the diameter

of the

screw exceeds 8 mm or the diameter of the smooth shank

exceeds 6 mm. The diameter of pre-drilled holes for non-self-

drilling screws should be D = 0.5

- 0.7

, but not more than

the inner diameter of the threaded part

The thickness of the member should be at least:

t=max{█(5d@(10d-30) ρ_k/400)┤

(5.38)

where

is the characteristic density [kg/m

]; and

is the screw diameter [mm].

General spacings and end and edge distances are present-

ed in Table 5.1. These values are valid for cross screw connec-

tions when the compressed and tensioned fasteners of the

screw pairs are placed in separate longitudinal rows parallel to

the grain, so that the spacing between the rows a

is 4d and the

staggered distance between the screw heads of a screw pair is

not more than 3t

parallel to the grain.

Different types or sizes of screws must not be combined

in the same connection. All screws must be positioned at the

same inclination angles ε and β in a member. The screws must

be positioned centrally to the connection force and screwed

deep enough so that the screw head is in full contact with the

member surface. The minimumpointside penetration depth of

the threaded part should be 6d. The members should be com-

pressed together so that no gaps are present

LVL suppliers provide their own specific instructions for

inclined screw connections with their products.

5.6 BOLTED AND DOWELED

CONNECTIONS

For bolted and dowelled connections the design rules are de-

fined for connections perpendicular to the grain of the face

veneer. The design of LVL connections follows Eurocode 5 Sec-

tions 8.5 and 8.6 with the exception of the embedment calcu-

lation. The rules for connection geometry are given in Section

5.2 and the rules for wood failure modes in Section 5.3 of this

handbook.

In laterally loaded connections of bolts and dowels up to

30 mm diameter arranged perpendicular to the grain, the fol-

lowing characteristic embedment strength values should be

used for LVL

f_(h,k)=(0,082 ∙ (1 - 0,01d) ρ_k)/((k_90 ∙ sin^2 α

(k_(C ) 〖∙ cos〗^2 β 〖+ sin〗^2 β) )

(5.39)

where

is the characteristic density [kg/m³];

is the angle between load and grain direction; for

softwood LVL-C / GLVL-C and

> 45°, α may be

assumed as 45°;

is the angle between bolt axis and wide face;

is the bolt diameter [mm];

is 1,15 + 0,015 for softwood LVL / GLVL; and

k_C=max{█(d/(

for softwood LVL / GLVL

(5.40)

5.7 FASTENING LVL PANELS TO FRAMES

Connections of LVL-C panels can be designed according to Eu-

rocode 5 instructions for timber-to-timber connections with

commonly available fasteners. The connection capacities and

minimum thickness of the frame depend on the panel, fastener

and frame material combinations. Capacities and dimension

for connections of LVL-C with LVL-P, glulam or solid timber

frames are presented in Table 5.5.

5.8 SPECIAL CASES

Many nail plate manufacturers have tested the anchoring

strength of their products for LVL-P members and the values

are of similar levels to C30 structural timber. The values are in-

cluded in their design software for trusses. LVL bottom cords

are used in nail plate trusses to give additional stiffness for the

floor part of attic trusses and fire resistance in cases where the

rest of the trusses may be exposed to fire.

Usually the anchoring devices are fastened to bracing pan-

els with laterally loaded connections to the wide face of the LVL

panels. However, glued-in rod or glued-in screw connections

on the edge face of LVL panels can be an efficient solution for

anchoring large bracing panels. They however require sepa-

rate type testing and production quality assurance and, in some

countries, also separate product certification. Glued-in rod or

glued-in screw connections at the edge face require a panel

thickness of at least 66 mm to fulfil the edge distance require-

ment of the connection.

h,k

0,082 ∙ (1 − 0,01 )

(

∙ sin

+ cos

) ∙ (

∙ cos

+ sin

)

= max �

( −2)

1,15

for softwood LVL / GLVL

= max �

5 (10 − 30)

400

(5.34)

189 (255)

Members should be pre-drilled when the diameter

of the screw exceeds 8 mm or the

diam ter of the smooth shank

exceeds 6 mm. The diameter of pre-drilled holes for non-

self-drilling screws should be

D = 0.5d - 0.7d,

but not more than the inner diameter of the

threaded part

The thickness of the member should be at least:

= max {

5 (10 − 30)

400

(5.38)

where

is the characteristic density [kg/m

]; and

is the screw diameter [mm].

Gen ral spaci gs and end and edge distances ar presented in Table 5.1. These values are

valid for cross screw connections when the compressed and tensioned fasteners of the

screw pairs are placed in separate longitudinal rows parallel to the grain, so that the spacing

between the rows

is 4

and the staggered distance between the screw heads of a screw

pair is not more than 3

parallel to the grain.

Different types or sizes of screws ust not be combined in the same connection. All scre s

mu t be positioned at the s me inclination angles

and

in a member. The screws m t be

positioned cent ally to th connection force and s rewed deep en ugh so tha the scr w

head is in full

tact with the member s rface. The minimum pointside penetration depth of

the threaded part should be 6

. The members should be compressed together so that no

gaps are present

LVL suppliers provide their own specific instructions for inclined screw connections with their

products.

5.6

Bolted and doweled connections

F r bolted and dowelled connections the design rules are defined for co nections

perpendicular to the grain of th face ven er. The design of LVL connections follows

Eurocode 5 Sections 8.5 and 8.6 with the exception of the embedment calculation. The rules

for connection geometry are given in Section 5.2 and the rules for wood failure modes in

Section 5.3 of this handbook.

In laterally loaded connections of bolts and dowels up t 30 mm diameter arranged

perpendicul r to the grain, th following ch racteristic embedment strength values should be

for LVL

h,k

0,082 ∙ (1 − 0,01 )

(

∙ sin

+ cos

) ∙ (

∙ cos

+ sin

)

(5.39)

where

is the characteristic density [kg/m³];

is the angle between load and grain direction; for softwood LVL-C / GLVL-C and

α > 45°, α may be assumed as 45°;

is the angle between bolt axis and wide face;

is the bolt diameter [mm];

1,15 + 0,015 for softwood LVL / GLVL; and

156

LVL Handbook Europe