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Category 2: Civil Structures
Bowstring Bridge - Zwankendamme, Belgium
Description of the bridge type and its
characteristics
In order to respond to the expansion of the Port
of Zeebrugge and the need for more capacity in
container traffic, the number of tracks of the “Bundel
Zwankendamme” has to be increased. Simultaneously,
the safety will be increased by replacing the level
crossing situated at Wulfsberge with a road bridge
crossing the railway tracks.
The solution of a large single-span bridge was chosen:
a bowstring bridge in steel with tie rods and prestressed
concrete decks. The abutments are in concrete and
founded on piles.
The characteristics of the bridge are:
• A single span of 87.98 m.
• Steel grade S355J2G3.
• The cross-sectional view.
• 2 lanes for vehicles, each 3.5 m wide.
• An emergency lane, 1 m wide.
• A cycling path, 3 m wide: two-way traffic, also
intended for occasional pedestrians.
• A high safety barrier (type IVB) and safety kerb (type
IVA) will be installed for road traffic safety.
• Four pot bearings will support the bridge.
• Each abutment is supported by 60 concrete screw
piles with a 60 cm diameter: 48 are vertical and 12 at
a 1/10th angle. All have the length of 18 m.
• The bridge is made of 560 tonnes of steel.
The bridge concept
As there will be a set of railway tracks under the bridge,
it is not possible to build intermediate pillars. They
would restrict the options of the track layout and they
would have a minimum distance to the railway tracks.
In addition, they would need to be dimensioned to cope
with the considerable accidental collision forces.
For the 88 m span the arch bridge is the best option
from a financial point of view. The construction height
(distance between the upper side of the road and the
bottom of the main girder) is very small for this kind of
span, only 85 cm.
The bridge has to be able to carry extraordinary loads of
360 tonnes, hence 12 axles of 30 tonnes.
The choice was made to provide one mixed cycling path
rather than two single paths + footpath because all the
cycling routes are on the south side of the bridge. The
north side contains nothing but industrial sites. Intense
usage by pedestrians is not expected.
Finally, the bowstring bridge is to be welded and
assembled in place with minimal interference with the
railway traffic.
The bridge will be put in place during a weekend
when railway traffic is interrupted, so with minimal
disturbance.
Calculation techniques, technical specifics
3D modelling of the bridge was carried out in
Scia Engineer 2011 to ensure the most accurate tension
calculations.
A global model has been built to calculate the strength,
stiffness and fatigue of the main steel structure and the
prestressed concrete decks.
Geometry, material properties, preconditions and loads
were all uploaded into the program.
A second-order check was also carried out in
Scia Engineer.
Everything has been dimensioned and checked
according to the Eurocodes.
This includes the following elements:
• Bearings
• Profiles
• Second-order check
• Prestressed decks
• Steel joints
• Several connections
• Abutment
• Girders between the arcs
Used modules
• Steel code check (EC)
• Stability
• Physical non-linear conditions
Software: Scia Engineer
