Don't panic Berlin EXPO Shanghai The Lower Inn Valley line as a ...

In 1566, Archbishop Johann Jakob Kuen von
Belasy had a tiny road carved into the
rock high above the gorge under extremely
difficult conditions.
Underside of the supporting structure Tendons (crosswise) together with support towers
In November 2009, the L109 also
saw the bottleneck between St. Johann
im Pongau and Grossarl relieved,
thanks to the new 50-metre-long
Egg-Graben Bridge. The
bridge replaces a narrow bend in
the road which has long been a
problem when transporting people,
animals and materials to and
from Grossarl village. As the mountain
region is so important for tourism
and is located near the famous
Liechtenstein gorge, the regional
government placed great importance
on an aesthetically pleasing
bridge. The slim design of the
bridge meant that the curve and the
structural plate had to be accurate
to within +/–0.5 cm.
PROLONGING THE SERVICE LIFE
The construction of the Egg-Graben
Bridge was implemented by ALPINE
and Grund-, Pfahl- und Sonderbau
GmbH. The plans and calculations
for the project were carried out in
cooperation with the Institute for
Structural Construction from the
Technical University of Vienna as
part of a research project about
bridges constructed without the use
of mild reinforcement. For university
professor Johann Kollegger and
his assistants Johannes Berger and
Zoran Bruschetini-Ambo, the construction
project was of particular
interest because the bridge was to
be constructed without using mild
reinforcement, but using electrically
isolated tendons (EIT). ‘It is the
first time ever that this kind of technology
has been used,’ explains Professor
Kollegger.
The tendons were encased in plastic
pipes, which provided a carefully
sealed shell to protect them from
corrosion (e.g. from the salt water
seeping in from the river). This
increases the service life considerably,
and as Professor Kollegger
points out, ‘The client gets a bridge
that can’t go rusty.’ The special
thing about EIT tendons is that – in
spite of the shell pipe – they can be
checked at regular intervals.
‘With the help of a special measuring
instrument, we can monitor the
TERMS
Reinforcement In construction, reinforcement means the
strengthening of a building material. Reinforcement can
consist of steel mats, rods or netting. With so-called mild
reinforcement, these will be incorporated into the concrete and
will considerably increase the load capacity of the components
in question. // If prestressed reinforcement is used, i.e.
stable wires (so-called tendons) that are incorporated into the
concrete and stretched, considerably less material is needed
to take the load of the construction and greater widths can be
spanned.
behaviour of the tendons,’ says Josef
Simader from Grund-, Pfahl- und
Sonderbau GmbH in relation to the
biggest advantage of this technical
innovation. ‘Changes in the electrical
resistance means that we can identify
any damaged sections.’ This will
reduce operation and maintenance
costs. Resistance measurements
will be carried out during construction
of the bridge as well as at regular
intervals after completion.
As mild reinforcement was not
used, fixing the tendons in place
was a particular challenge. In the
end, the tendons were stretched
crosswise and supported by support
towers at the points where they intersected
(see figure above).
Residents and visitors to the Grossarl
Valley have probably not even
realised the kind of technical innovations
that are being implemented
in their area, but it is something
that they will now be able to benefit
from every single day. //
49
Excavation for
the abutment on
the geologically
demanding
terrain posed
a particular
challenge for
the construction
machinery.