B+H
Bau is renewing two railway bridges in Steinach, Germany for Deutsche Bahn. The
formwork plan and wall formwork come from PASCHAL. The PASCHAL Maturix solution
was used to calculate the right time to dismantle the formwork.
Five prefabricated parts
for the new railway bridge on Kirchstrasse in Steinach were built on a nearby
field factory. LOGO.3 wall formwork was used for the frame structure and PASCHAL
TG 60 shoring system for the slab formwork. With the help of the loops (one can
be seen on the middle component above), the 100-tonne prefabricated parts were
lifted with a mobile crane and pushed into the original position of the old
bridges
Instead of an Easter egg
hunt, the employees of B+H Bau played a kind of Lego game in XXL format this
spring. They were based in Steinach, Germany in the Black Forest: Two aging
railway bridges on Kirchstrasse and Sarach were demolished and the new
prefabricated bridges were slid into place. After twelve days of full closure,
the tracks were reopened on 6 April and the Baden Black Forest Railway was once
again able to run unhindered through Steinach and take passengers from
Karlsruhe via Offenburg to Villingen-Schwenningen and on to Constance on Lake
Constance.
On 25 March 2024, the
Kirchstrasse and Sarach railway bridges were closed in order to remove the
tracks and demolish the existing structures. Not far from the old bridges,
construction work on the new bridges has been underway since mid-January. The
frame structures were built in prefabricated construction by the company B+H
Bau from Drolshagen in North Rhine-Westphalia. The company works exclusively
for Deutsche Bahn and was awarded the contract to rebuild the two railway
bridges – which were built in 1909 and 1910 – in autumn 2023. B+H's order
volume for the renewal of the two bridges was around 5.5 million euros.
Heavy equipment was then
used over Easter. The prefabricated parts were loaded individually with a
500-tonne mobile crane onto a so-called SPMT vehicle – a self-propelled modular
transporter. This modular vehicle with its own drive was used to transport the
prefabricated parts from the field factory to the old bridge site. At Sarach in
the south of Steinach, a 600-tonne crawler crane was ready to lift in three
prefabricated parts. A good two kilometres away in the centre of Steinach, a
similar spectacle took place: a 650-tonne mobile crane lifted five individual
bridge sections into position; the B+H employees then assembled them using the
contact construction method. 'The individual sections of the new bridge weigh
around 100 tonnes each. You can't produce such large sections in a production
hall and transport them here. This is why Deutsche Bahn allocated open spaces
to us nearby where we prefabricated the half-frame structures with integrated
wing walls parallel to the track completely in a field factory', explains Marc
Weißgräber, technical manager at B+H Bau and also project manager.
Prefabricated
components are formed in the field factory
The field factories were
located about 100 metres from Kirchstrasse and about 30 metres from the Sarach
bridge. Construction work started in mid-January and the two bridges were built
within two months. The final concrete was placed on 20 March.
Three years ago, B+H Bau
used a formwork solution from PASCHAL for a project in Hausach, Germany, ten
kilometres away from Steinach. If a project is being carried out in the Black
Forest or, as in this case, directly in Steinach, where PASCHAL has its head
office, it makes sense for the construction company to turn to the formwork
manufacturer from Baden, Germany, for a quotation. The technical manager was
very satisfied with the precise planning and formwork preparation. This was the
only way that work on the construction site could proceed so smoothly and
quickly. 'We approached PASCHAL in October. I was on site twice to go through
the formwork plans and I had the complete formwork planning on the table before
Christmas,' recalls Marc Weißgräber.
Precise
planning of formwork cycles saves time on the construction site
There were two main
challenges in the Steinach railway subway project. According to Marc
Weißgräber, one challenge was the fact that the new bridge over Kirchstrasse
did not cross the tracks at right angles, but was built at an angle of
approximately 70 degrees to the track axis. 'The structure therefore looks a
bit like a parallelogram', says Marc Weißgräber. Even the demanding schedule could only be realised
with precise planning. 'We had to erect a total of 13 prefabricated parts in
eight weeks. The lightest prefabricated part weighed 40 tonnes and the heaviest
weighed 120 tonnes. Creating this with as little formwork and effort as
possible was not easy', summarises the B+H project manager. This makes it all
the more important to plan the sequence of the formwork cycles precisely in
advance. The complete work sequence – five cycles for the bridge on
Kirchstrasse, three cycles for the one on Sarach – was planned by Sergej
Winter, project manager at PASCHAL; Ingolf Fischer, Head of Formwork
technology, carried out the structural calculations for the shoring systems.
LOGO.3 wall formwork was used; one-metre-high panel elements were used for the
60 cm high foundation – the formwork for the walls was 5.5 metres high.
The new bridge on
Kirchstrasse consists of five prefabricated parts. 'Once the foundation
formwork had been erected, we constructed the inner core through which the cars
drive – i.e. the wall with the superstructure and the ceiling area – each in
“one pour”', explains Marc Weißgräber. The foundation formwork area was 80 m2
in each case, the wall formwork for the frame structure at Kirchstrasse was 300
m2 and at Sarrach 110 m2. In addition, they each required 70 m2 of slab
formwork, for which PASCHAL's TG 60 shoring system was used.
Photo 1 clearly shows the
green tubes protruding from the foundation. 'When the component is pushed into
place, it stands on a 300 mm-high steel girder; we then placed the concrete
through these green tubes so that the structure stands firmly on the ground',
explains Marc Weißgräber.
Probe
instead of concrete test cube: Measuring concrete strength with PASCHAL Maturix
For the construction
project in Steinach, B+H Bau measured the temperature of the concrete for the
first time using the PASCHAL Maturix solution. The device measures the strength
development of the concrete using a probe that is embedded in the concrete. A
measuring device shows the foreman on a monitor or laptop whether the concrete
is firm enough to dismantle the formwork. 'With the help of PASCHAL Maturix, it
is possible to dismantle the formwork two to three days earlier and there is no
need to produce a concrete test cube, which is always a cost factor. The use of
the measuring device was very advantageous here, as construction time was
tight,' states the technical manager of B+H Bau.
In the conventional
procedure for determining concrete strength, a concrete test cube with an edge
length of 20 cm is produced. This so-called early strength cube is stored on
the construction in the same temperature environment and is taken to the
concrete laboratory after three days. 'There, the cube is crushed with the
press. If it only breaks at 45 Newton millimetres per square millimetre, we
know that we can now dismantle the formwork', explains Marc Weißgräber. His
conclusion of the test operation of PASCHAL Maturix is positive: 'It's much cheaper and easier if you can use
this device.'
Tracks
are laid and rail traffic flows. What now?
The B+H Bau employees'
work did not end with the precision work carried out over the Easter holidays
but continued up until the opening of the tracks for the Black Forest railway
at the beginning of April. At peak times, 22 employees were on site in
Steinach. Some of them will be working on the two construction sites until the
end of July. What's on the to-do list: Disposal of rubble and excavation
material, facing the bridge with brickwork, installing railings and re-laying
various pipes. Finally, a landscaping subcontractor will plant hedges and trees
'so that everything looks tidy again'. Marc Weißgräber is satisfied with the
co-operation with PASCHAL and is already preparing the next project in the
Black Forest: 'Following on from the Steinach project, we are using wall
formwork LOGO.3 for a project in Breitnau near Freiburg.'
The strength development
of the concrete was measured using the PASCHAL Maturix solution. This rendered
the construction of a concrete test cube unnecessary and meant that the
formwork could be dismantled as early as possible.
