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Modelling of strengthened connections for large span truss structures

Kobel, Peter (2011) In TVBK VBK920 20082
Division of Structural Engingeering
Abstract
Because of its large ratio between strength and weight timber is a material very suitable for
large span structures. For large spans of more than about 30 m, usually truss structures are
adopted. The problem of large span timber truss structures are the expansive and complex
nodes that have to be adopted, normally single or multiple slotted-in steel plates in
combination with a number of dowels.
In order to find a more efficient and economical solution for timber nodes, a novel truss
node has been developed at SP-Trätek in Borås. The node consists of a single large-
diameter dowel which connects the diagonals with the chords. Additionally, self-tapping
reinforcing screws are applied to prevent premature splitting failure and... (More)
Because of its large ratio between strength and weight timber is a material very suitable for
large span structures. For large spans of more than about 30 m, usually truss structures are
adopted. The problem of large span timber truss structures are the expansive and complex
nodes that have to be adopted, normally single or multiple slotted-in steel plates in
combination with a number of dowels.
In order to find a more efficient and economical solution for timber nodes, a novel truss
node has been developed at SP-Trätek in Borås. The node consists of a single large-
diameter dowel which connects the diagonals with the chords. Additionally, self-tapping
reinforcing screws are applied to prevent premature splitting failure and also to increase
the strength and the stiffness of the node.
In the course of this thesis a full-scale test series was carried out to investigate the
behaviour of the node. 15 glulam specimens with reinforced single large-diameter dowel
connections were tested in load controlled tensile tests. Besides various configurations of
self-tapping screws also lateral prestressing was used as a reinforcement measure.
It was found that the bearing capacity of the connection can be significantly increased by
applying self-tapping screws. Reinforcing screws effectively impede splitting of the timber
if placed near the loaded end of the connection, where major lateral deformations occur.
However, reinforcing screws cannot prevent the formation of a shear plug, which was
observed to be the ultimate failure mode.
Lateral prestressing of the connection also proved to be an effective reinforcement
measure, as splitting can be prevented completely. By applying large lateral prestresses the
failure mode changes to a combined shear and tensile failure which results in a higher
bearing capacity. (Less)
Please use this url to cite or link to this publication:
author
Kobel, Peter
supervisor
organization
course
VBK920 20082
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
TVBK
report number
TVBK-5198
ISSN
0349-4969
language
English
id
3358420
date added to LUP
2013-01-10 13:14:28
date last changed
2013-01-10 13:14:28
@misc{3358420,
  abstract     = {Because of its large ratio between strength and weight timber is a material very suitable for 
large span structures. For large spans of more than about 30 m, usually truss structures are 
adopted. The problem of large span timber truss structures are the expansive and complex 
nodes that have to be adopted, normally single or multiple slotted-in steel plates in 
combination with a number of dowels. 
In order to find a more efficient and economical solution for timber nodes, a novel truss 
node has been developed at SP-Trätek in Borås. The node consists of a single large-
diameter dowel which connects the diagonals with the chords. Additionally, self-tapping 
reinforcing screws are applied to prevent premature splitting failure and also to increase 
the strength and the stiffness of the node. 
In the course of this thesis a full-scale test series was carried out to investigate the 
behaviour of the node. 15 glulam specimens with reinforced single large-diameter dowel 
connections were tested in load controlled tensile tests. Besides various configurations of 
self-tapping screws also lateral prestressing was used as a reinforcement measure. 
It was found that the bearing capacity of the connection can be significantly increased by 
applying self-tapping screws. Reinforcing screws effectively impede splitting of the timber 
if placed near the loaded end of the connection, where major lateral deformations occur. 
However, reinforcing screws cannot prevent the formation of a shear plug, which was 
observed to be the ultimate failure mode. 
Lateral prestressing of the connection also proved to be an effective reinforcement 
measure, as splitting can be prevented completely. By applying large lateral prestresses the 
failure mode changes to a combined shear and tensile failure which results in a higher 
bearing capacity.},
  author       = {Kobel, Peter},
  issn         = {0349-4969},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVBK},
  title        = {Modelling of strengthened connections for large span truss structures},
  year         = {2011},
}