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A feasibility study of a network arch bridge with glulam arches

Nylander, Erik LU (2012) VBK920 20112
Division of Structural Engingeering
Civil Engineering
Abstract
The drive of using more renewable material has increased the interest in timber bridges. This makes it more interesting in looking in to new ways of constructing timber bridges. Most timber bridges for road traffic are using an arch with a hanging deck suspended from the arch using vertical hangers. This master thesis has looked at the possibility of using a system (developed for steel arch bridges) that is using inclined hangers, “the network arch”. This system has proven to greatly lessen the bending moment in the arch for steel arch bridges.
A parametric study has been performed to decide the influence of the different parameters of the bridge. The study was made using a finite element program to calculate different influence lines.... (More)
The drive of using more renewable material has increased the interest in timber bridges. This makes it more interesting in looking in to new ways of constructing timber bridges. Most timber bridges for road traffic are using an arch with a hanging deck suspended from the arch using vertical hangers. This master thesis has looked at the possibility of using a system (developed for steel arch bridges) that is using inclined hangers, “the network arch”. This system has proven to greatly lessen the bending moment in the arch for steel arch bridges.
A parametric study has been performed to decide the influence of the different parameters of the bridge. The study was made using a finite element program to calculate different influence lines. These influence lines have then been the basis of the study. The study showed that by changing the stiffness of the arch and hangers the influence lines for the designing bending moment could be changed and the point for the critical section could be moved.
The study has also showed that the problem with relaxing hangers was bigger than anticipated. Hanger relaxation is a problem for network arches and is due to the fact that a partial load of the bridge will deform the arch in a sideways movement. This movement will decrease the distance between the nodes for some of the hangers making them “to long” to take any load.
The study was made on a hanger constellation using the same angle for all of the hangers. It was proven that the problem with relaxation was biggest close to the supports. This proved that another hanger constellation using a constant or parabolic change of hanger inclination would probably lessen the risk of relaxing hangers.
The feasibility of the system was then tested by designing a 50 m long and 10 m wide network arch bridge with a hanger inclination of 55 degrees. A reference bridge with a more conventional design with vertical hangers has also been designed.
This design showed that by using the network arch system the bending moment that was achieved was almost nine times smaller and the cross-section of the arch was almost half the size. The lessening of the bending moment also had a great impact on the tension perpendicular to the grain of the arch, a load that is a big problem for arches especially when using the Eurocode design standards. (Less)
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author
Nylander, Erik LU
supervisor
organization
course
VBK920 20112
year
type
H3 - Professional qualifications (4 Years - )
subject
report number
TVBK-5211
ISSN
0349-4969
language
English
id
3159858
date added to LUP
2012-10-31 15:26:49
date last changed
2012-10-31 15:26:49
@misc{3159858,
  abstract     = {The drive of using more renewable material has increased the interest in timber bridges. This makes it more interesting in looking in to new ways of constructing timber bridges. Most timber bridges for road traffic are using an arch with a hanging deck suspended from the arch using vertical hangers. This master thesis has looked at the possibility of using a system (developed for steel arch bridges) that is using inclined hangers, “the network arch”. This system has proven to greatly lessen the bending moment in the arch for steel arch bridges.
A parametric study has been performed to decide the influence of the different parameters of the bridge. The study was made using a finite element program to calculate different influence lines. These influence lines have then been the basis of the study. The study showed that by changing the stiffness of the arch and hangers the influence lines for the designing bending moment could be changed and the point for the critical section could be moved.
The study has also showed that the problem with relaxing hangers was bigger than anticipated. Hanger relaxation is a problem for network arches and is due to the fact that a partial load of the bridge will deform the arch in a sideways movement. This movement will decrease the distance between the nodes for some of the hangers making them “to long” to take any load.
The study was made on a hanger constellation using the same angle for all of the hangers. It was proven that the problem with relaxation was biggest close to the supports. This proved that another hanger constellation using a constant or parabolic change of hanger inclination would probably lessen the risk of relaxing hangers.
The feasibility of the system was then tested by designing a 50 m long and 10 m wide network arch bridge with a hanger inclination of 55 degrees. A reference bridge with a more conventional design with vertical hangers has also been designed.
This design showed that by using the network arch system the bending moment that was achieved was almost nine times smaller and the cross-section of the arch was almost half the size. The lessening of the bending moment also had a great impact on the tension perpendicular to the grain of the arch, a load that is a big problem for arches especially when using the Eurocode design standards.},
  author       = {Nylander, Erik},
  issn         = {0349-4969},
  language     = {eng},
  note         = {Student Paper},
  title        = {A feasibility study of a network arch bridge with glulam arches},
  year         = {2012},
}