2005 - Putzmeister

Special concrete
Large boom concrete pumps inject
"Bügelbauten" bookend buildings
With the completion of the two 46 m tall
office towers, the last construction section
of the new Berlin main train station
began at the end of July 2005. The imposing
building is being constructed on the
site of the former Lehrter train station
and, after completion, will be used as the
central terminal for north/south and
east/west rail transport in the German
capital. According to forecasts, 300,000
passengers and visitors are expected at the
Lehrter train station each day.
The pump service provider LICHTNER
used three Putzmeister concrete pumps to
inject the complicated floor structure of
steel sections with a specially developed
concrete, as well as to concrete the floors.
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Berlin's first main train station
As in London and Paris, Berlin never
had a central main train station in the
past. Due to the star-shaped railway
network, the railway lines ended at the
edge of the capital city. At the end of
the 19th century, a suburban railway
line connected the city's most important
long-distance train stations.
The old Lehrter train station, opened in
1871, was severely damaged in the
Second World War, and the ruins of the
former building were blasted at the end
of the 50s. Thereafter, the Berlin suburban
railway used the site as a stopping
point. After the fall of the Berlin
wall, intensive work went into plans
for a central traffic node for the
German capital city. In 1998, work on
the new train station began.
At the end of May 2006, shortly before
the Football World Cup, the Lehrter
train station is to be officially opened
as "Europe's most modern train terminal"
– according to DEUTSCHE
BAHN AG.
The aboveground part of the new Berlin
main train station (east/west direction) has
four platforms for long-distance and regional
trains and two platforms for suburban
railway traffic, 10 m above street level. For
the north/south connection, eight platforms
for long-distance and regional trains as
well as two for the underground line U5
will be constructed 15 m below ground.
A huge glass roof with a length of 321 m,
which is installed above the east/west
wing, will act as protection against bad
weather and will allow daylight to reach
even the deeper floors.
The critical section of the project is the
completion of the bookend buildings. These
are two 46 m tall office buildings which, at
a length of 87 m, straddle the east-west line
like bridges at the intersection of the railway.
The two twelve storey buildings were
initially constructed as four vertical tower
halves, which were tilted by 90° in summer
2005 and welded. This procedure, which is
not carried out every day, was chosen to ensure
that the railway traffic flowing beneath
the buildings did not have to experience
disruption caused by a long construction
period.
The carcass construction work for the solid
structure of the bookend buildings was
carried out by WAYSS & FREYTAG
INGENIEURBAU AG.
Highly effective deflocculant helps the
concrete spread into "dead angles"
The four bookend buildings consist of
numerous steel pipe sections which are
designed as loadbearing composite constructions.
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Lowering of the bookend buildings over the east/west line of the Lehrter train station (Photo: DB AG/Reiche)
Even in the narrowest of spaces, the two
Putzmeister M 42 and M 52 can be set up by
the concrete pump service provider LICHTNER
– as shown here for concreting the floors
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Amongst other things, the pylons, the
external and internal supports of the bases
of the bookend buildings and the lattice
girders of the four 1,250 ton bookend halves
with their numerous upper, middle and
lower flanges were injected with concrete.
The contract for this work was awarded to
LICHTNER pump service provider from
Velten, which, over a period of months,
used its Putzmeister truck-mounted
BSF 36.16 HLS, BSF 42.16 H and
BSF 52.16 H concrete pumps for the work.
The steel sections contain a very densely
set reinforcement and, up to a height of
10 m, are injected with a specially developed
concrete with strength class C45/55 in
one operation. The mixture breakdown
includes an increased fines content and a
highly effective plasticising admixture
based on polycarboxylatether (PCE), which
displays an even higher deflocculation
effect compared with the familiar super
deflocculants. As the pumped concrete contains
practically no more air particles, and
has a very free-flowing consistency (F5 to
F6), additional shaking is not necessary.
Injection through 150 m long 65 mm
delivery hose
At the start of the injection work, the boom
length of the BSF 36.16 HLS was still
sufficient. As the construction progressed,
however, LICHTNER started to use its
concrete pumps with 42 and 52 metre
vertical reach. In order to also be able to
Up to three concrete pumps simultaneously inject the numerous
steel sections of the bookend buildings. Picture shows M 36.
reach the farther removed filler pipes, a
tapering, which reduced the line diameter
to 65 mm, was connected to the machine's
boom tip instead of an end hose. The
connection of up to 150 metres of hose
meant a significantly increased working
range could be achieved. As expected, the
hydraulic pressure of the pumps increased,
but remained within a reasonable limit.
Filler pipes situated beneath the steel sections
fill them with quantities of 5 to 6 m 3 .
The slow ascent of the concrete in the constructional
element discharges the available
air upwards. The filler pipes in the injected
steel sections are closed with guillotines
and concrete is prevented from escaping by
cutting the line. Injection of the bookend
buildings started in April 2005 and completion
is planned for the end of 2005.
In addition to injecting the steel sections
with special concrete, the two LICHTNER
large boom pumps BSF 42.16 H and
BSF 52.16 H are also used for concreting
the floors. Their boom length means they
can also reach higher levels of the bookend
buildings. To do this, the large boom
pumps need a C 40/50 concrete with a
maximum particle size of 16 mm, and the
individual sections each hold approximately
120 m 3 . For this work too, the pipe at the
boom tip of the truck-mounted concrete
pump was reduced to 65 mm diameter
through the addition of a tapering and a
flexible hose with a length of up to 30 m
was connected.
The floors are concreted with the boom tip extended
and with a 65 mm delivery hose attached
Guillotines are used to close the steel sections after
injection
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