VSH Turòa nad Bodvou - Nemetschek Scia

Introduction
Anyone driving from Heerenveen to the Afsluitdijk over the A7
will discover that Sneek is still a considerable hindrance - the A7
motorway is interrupted by a 4-kilometre stretch of the N7 bypass to
the south of Sneek. This situation will last until mid-2008 when the
last section of N7 will have been upgraded to the A7 motorway.
The eastern half of this southern bypass section will be upgraded
over the existing route. About midway along the existing N7
section, the river Geeuw, the railway line from Sneek to Stavoren,
the exit road Sneek-IJlst and a dikeroad will be crossed by the
route of the new A7 motorway. In this new situation there will
be an aqueduct under the Geeuw, at which over the access road
on the west side viaducts will be constructed for the railway, the
Sneek-IJlst road and in addition a local road that runs over the Alde
Himdyk. The western half of the new A7 branches away from the
existing N7 from the aqueduct and goes round the business park
De Hemmen for which there are expansion plans.
Geeuw project
The structural Geeuw project is divided into ten subway sections,
one water cistern, two prefab traffic viaducts, one railway viaduct
and one aqueduct with the connecting pieces and caps. All insitu
concrete structures were detailed by Witteveen+Bos, see next
page. The railway viaduct was detailed by TCE.
Railway viaduct
The Sneek-Stavoren line is a single-track, non-electrified railway. The
railway viaduct over the entrance to the aqueduct is constructed as
a pre-stressed trough beam. The beam was placed directly on the
corners (without intermediate abutments) on four bored piles. The
piles were placed at night when the line was out of service.
Railway of ‘Geeuw’ aquaduct
The project concerned a railway viaduct for the Sneek-
Stavoren line, this is a single-track, non-electrified railway.
The railway viaduct is constructed as a pre-stressed trough
beam. The beam was placed directly on the corners (without
intermediate abutments) on four bored piles. The piles were
placed at night when the line was out of service. These
concrete piles are 1.2 metres in diameter and are approximately
36 metres deep. They are reinforced over the top 14
metres.
The rail trough is completely separate from the aqueduct.
Only the final transverse restraint of the trough is carried
by the outer walls of the underlying aqueduct. The railway
trough was constructed next to the railway dike and was slid
into place in September 2006, with the railway being out of
service for less than a weekend.
These concrete piles are 1.2 metres in diameter and are approximately
36 metres deep. They are reinforced over the top 14
metres.
The rail trough is completely separate from the aqueduct. Only the
final transverse restraint of the trough is carried by the outer walls
of the aqueduct. The railway trough was constructed raised next
to the railway dike and was slid into place in September 2006, with
the railway being out of service for less than a weekend. Following
this, the construction of the aqueduct that runs underneath was
begun.
The aqueduct crosses the railway at an angle of approximately 67°.
The bored piles under the railway trough are positioned at right
angles to the railway line at each end of the trough viaduct. The
spanning of the trough is approximately 33 metres, at a construction
height of 2.15 metres. The floor screed is 0.65 metres thick.
Project strategy
The railway viaduct is a slender design with relatively thin trough
walls. Thus the percentage of reinforcement in the walls and
floors is high. A large amount of reinforcement comes together
at the end of the trough beams. The distribution of forces from
the prestressing anchors results in a quantity of split reinforcement.
The encasement tube for the prestressing cables runs through the
split reinforcement. The split reinforcement is crossed by reinforcement
from the floor. This reinforcement functions as a tension
rod between the two walls. In addition, the walls of the trough
beam are reinforced by transverse braces, torsion braces, flank
bars, suspended reinforcement for the floor and compression
reinforcement. Compression reinforcement is required to meet
the ultimate limiting condition for the compression zone height to
prevent brittle failure of the structure. This quantity of reinforcing
steel can lead to problems if the position of the bars is not carefully
worked out. The use of Allplan enabled a number of conflict
points to be solved immediately by making certain bars a different
shape. Checking the complex reinforcement is now much easier
for the structural engineer, because the reinforcement can be seen
on a 3D animation screen. A three-dimensional image in combination
with two-dimensional cross-sections gives a good picture of
the actual situation. This manner of working has helped to avoid a
large number of conflict points during construction.
Project technical data
Project name: Construction of Geeuw aqueduct Sneek
Principal: Province of Friesland / ProRail
Location: Sneek
Length: 38,95 metres
Span: 32,95 metres
Width: 7,45 metres
Height: 1,95 metres
Quantity of concrete: approx. 310 m³
Quantity of steel reinforcement: approx. 53,000 kg
Realisation Geeuwaquaduct Sneek - Spooraquaduct
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