[322/03] Francke - Ingenia

NILS FRANCKE
ØRESUNDBRO KONSORTIET
INFRASTRUCTURE
The Øresund Bridge
– linking
Scandinavia
to the
continent
The Øresund Bridge, one of the
largest infrastructure projects in
the history of Europe, is set to
change southern Scandinavia forever.
A combined tunnel and bridge link
carrying the motorway and railway has
replaced the existing ferry routes
between the Danish capital of
Copenhagen and the Swedish regional
capital of Malmö.
The Øresund Bridge comprises three
major civil works projects: a 4 km
artificial island, the world’s largest
immersed tunnel for both railway and
motorway, as well as the 7.8 km bridge
with a cable-stayed high bridge as the
impressive centrepiece.
Almost five years after the civil works
began the Øresund Bridge was opened
to traffic on 1 July 2000. This 3 billion
USD project was completed on
schedule as well as on budget.
The new and greatly improved
infrastructure will further the integration
of the area now known as the Øresund
Region, a cross-border region with
roughly 3.5 million Danish and Swedish
inhabitants. Combining the best of
Copenhagen and Malmö, the Øresund
Region will have a major impact on
Northern Europe in terms of education,
science, finance and culture. But
before full integration can be achieved,
a substantial amount of legislation has
to be introduced, not least within the
labour market and education.
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INFRASTRUCTURE
Figure 2: The route of the Øresund Bridge
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The skill with which the contractors
successfully planned and executed the
construction of the tunnel, the bridge
and the major dredging works can
largely be ascribed to the Design-and-
Construct concept which forms a part
of all the major contracts. Optimum use
of prefabrication also played a key role.
As the Design-and-Construct concept
lays down precise functional
requirements for the whole project,
contractors are responsible for the
detailed design as well as for the
construction work.
Rigorous environmental requirements
were in force throughout the
construction period, governing both the
construction of the link and the impact
of the completed link on the
surrounding environment. As the Danish
and Swedish governments had
stipulated that the link must not block
the water flow through Øresund, careful
trimming of the link’s design reduced
the calculated blocking effect from 2.3
per cent of the water flow to 0.5 per
cent prior to final adjustment.
Compensation dredging in and around
the alignment further reduced the
blocking effect.
Dredging and reclamation
The dredging and reclamation contract
included the initial construction works
for the fixed link which began in August
1995. Over four years a total of 7.5
million cubic metres of (mainly) seabed
material was dredged, two thirds in
Danish waters and one third in Swedish
waters. The seabed consists of gravel
and stone, clay till and limestone with
flint layers.
Dredging was carried out by a
number of dredgers, traditional bucket
dredgers as well as a specialised
cutter/suction dredger for the tunnel
trench.
The objective was for the
completed link to have no net effect
on the water flow and on the
movement of salt and dissolved
oxygen through Øresund to the Baltic
Sea. Consequently the size and shape
of the peninsula and the island were
optimised to reduce the blocking of
the water flow through Øresund.
Further reduction to zero blocking was
achieved by compensation dredging.
All dredged seabed material was
reused in the reclaimed areas which
cut sediment spill to a minimum and,
in addition, reduced the need for
dumping sites as well as for import of
sand and gravel.
The dredging works included:
● Work harbours and access channels
at the artificial island and the artificial
peninsula
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INFRASTRUCTURE
● A trench for the immersed tunnel
● Relocation of the Drogden Channel
● Relocation and deepening of the
Flinte Channel
● Compensation dredging to achieve
zero blocking of the water flow
The reclamation works included:
● The artificial peninsula at Kastrup
● The artificial island which connects
the tunnel and the bridge
The 0.9 km 2 peninsula at Kastrup
serves to bring together the passenger
track from the underground station at
Kastrup Airport with the freight track
running north of the airport. The
motorway along the northern edge of
the peninsula joins the railway at the
entrance to the tunnel portal. The
peninsula also has a track leading to a
railway maintenance area.
The 1.3 km 2 artificial island south of
the natural island of Saltholm forms the
transition between the tunnel and the
bridge. From the tunnel portal on the
western end of the island, the motorway
runs parallel to the railway to the eastern
end, from where the railway runs under
the motorway on to the two level bridge.
The reclamation areas were
constructed as basins surrounded by
coarse pebble bunds lined with a
geotextile membrane. The basins were
then backfilled with clay to prevent the
suspended sediment from escaping.
Reclamation was carried out in stages
as the bunds were completed,
surrounding the individual sections.
During filling at the artificial island, the
traffic corridor for the high-speed
railway was compacted to minimise any
differential settlements which could
interfere with the passage of highspeed
trains. The reclaimed areas were
completed with revetments, comprising
layers of armour stones and filter
stones. The revetments protect the
tunnel against flooding during storms
and high water.
The immersed tunnel
The tunnel extends approximately 4 km
from the Danish coast at Copenhagen
Airport to the artificial island in the
middle of Øresund. The tunnel
comprises five parallel tunnel tubes –
two for the railway, two for the
motorway plus a small tunnel as an
escape gallery. The sheer size of the
tunnel and the shallow waters in this
part of Øresund made an immersed
tunnel the natural choice.
Figure 3: Aerial view of tunnel factory
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INFRASTRUCTURE
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Figure 4: Aerial view of tunnel section being towed to site
The immersed tunnel was
constructed from twenty prefabricated
concrete tunnel elements. The elements
were cast at a purpose-built factory 12
km north of the tunnel site. Each
element was towed to the tunnel site by
four tug boats and lowered into the
tunnel trench with enormous precision,
using GPS satellite navigation.
The fact that casting took place
under cover allowed for efficient and
smooth production, regardless of the
weather. As a positive side effect the
number of work-related accidents was
subsequently reduced.
Each tunnel element is 176 metres
long, 49 metres wide, approximately 9
metres high and weighs around 57,000
tonnes. Each element was cast in eight
sections at the tunnel factory each of
which was cast in one 30 hour cycle.
Each section was cast against the
previous section and the element was
then gradually pushed out of the
casting hall and on to a ramp, in what
was, in effect, a giant lock system.
When all eight sections were cast and
one complete 176 metre element was
ready, a sliding gate was closed behind
the element, and the basin was flooded
until the element floated.
The element could then be pulled
into the deep end of the basin to await
being towed to the tunnel site. After the
water inside the lock had reached sea
level allowing the element to be towed
out, the next two elements would be
cast. Two parallel production lines
allowed for maximum output and
efficiency.
The towing of the elements
demanded great skill and precision. The
57,000 tonne element was almost
completely immersed during towing
and the changing currents in Øresund
had to be calculated in great detail
before the towing-out. This operation
took place in the Drogden Channel in
Western Øresund, which is an
international shipping route used by
some 40,000 ships per year. Early in
the construction phase a radar station
was established to monitor shipping
and guide vessels through the work
areas thus avoiding any major
accidents. During operations only a
handful of collisions and minor incidents
took place involving work vessels and
shipping, causing material damage only.
Not once was a tunnel element
damaged due to a collision. However,
on 4 August 1998, the accident that
everybody was dreading took place: a
tunnel element was flooded while being
positioned in the tunnel trench. Before
tow-out the tunnel tubes in the element
were sealed off with steel bulkheads.
Due to a number of mistakes one
bulkhead was not properly secured and
succumbed to the water pressure. In a
matter of seconds all five tunnel tubes
in the large concrete element filled with
water, and in accordance with
procedures the element was
immediately lowered into the trench,
but several metres out of position. It
took Øresund Tunnel Contractors eight
weeks to inspect, repair and eventually
move the tunnel element into its correct
position.
During this period the lowering gear
and platforms were attached to the
flooded element so the contractor was
unable to save time simply by building
the tunnel from both sides at the same
time. However the tunnel factory
continued to produce the tunnel
elements and once the flooded tunnel
element had been repaired and placed
in the correct position, the tow-out and
construction of the rest of the tunnel
elements was carried out at high
speed. As a result, despite this major
setback, the tunnel was constructed
ahead of schedule.
The Bridge
For the bridge section, which connects
the artificial island with the Swedish
coast at Lernacken, a cable-stay
design was chosen for the high bridge
due to the weight of the combined
railway and motorway link. The entire
bridge is 7.8 km long of which the high
bridge accounts for 1,092 metres. The

INFRASTRUCTURE
Figure 5: Floating crane carrying deck section
The cables of the high bridge are
arranged in a classic harp pattern and
anchored to the superstructure truss at
20 metre intervals. Supported primarily
on two pairs of pillar shafts the bridge is
symmetrical from the centre of the
navigation span. It has intermediate
side span piers to limit the deflections
of the 490 metre main span. Each
pylon consists of twin, cast-in-situ
concrete towers extending to a height
of 204 metres above sea level. Cables
are anchored in the pylons at 12 metre
intervals. The foundations for both the
pylons and the side span piers are
prefabricated concrete caissons,
located in the hard limestone, 14 to 17
metres below sea level.
490 metre long main span of the high
bridge crosses the Flinte navigational
channel, which is used by
approximately 10 per cent of the
vessels passing through Øresund. The
majority of shipping passes through the
Drogden navigational channel along the
Danish coast.
As was the case with the tunnel, a
high level of prefabrication was used in
the construction of the bridge. Apart
from the pylons which were cast in situ,
all other components – caissons, pillar
shafts and bridge girders – were
produced on land and transported to
the bridge by the large floating crane,
the ‘Svanen’. This self-propelled crane,
a unique and highly versatile tool,
positioned the heaviest concrete
caissons and pillar shafts with great
precision. For two years ‘Svanen’ made
regular trips between Sundlink
Contractors’ bridge factory in Malmö
North Harbour and the bridge line,
constructing the two approach bridges
and the high bridge like a giant Lego kit.
The superstructure of the bridge is a
composite steel-concrete structure with
truss girders. The upper deck carries
the motorway and the lower deck
contains the railway. The bridge is the
largest of its kind in the world carrying
both passenger trains, freight trains and
motorway traffic.
Figure 6: View of completed bridge from sea level looking towards tower
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INFRASTRUCTURE
approach bridges were produced by
Dragados in Cadiz in Southern Spain
and subsequently towed to Sweden in
pairs, complete with concrete
motorway deck.
The high bridge is carried by a total
of 80 pairs of cables, ten in each
direction from each pylon leg. Each
cable consists of between 68 and 73
strands. A strand consists of seven 5
mm wires. The wires are galvanised,
waxed and encased in plastic casing.
Each cable has a tensile strength of
2,000 tonnes and the combined length
of all cables is about 25 km. The total
weight is about 2,300 tonnes.
Following the inauguration of the
Øresund Fixed Link on 1 July 2000
approximately 500,000 vehicles
crossed the Øresund Bridge during the
first month. Information about traffic
and toll prices etc. can be seen at
www.oeresundsbron.com. The photo
files of the Øresund Bridge are available
at www.bridgephoto.dk. ■
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Figure 7: Side view of bridge to show cable pattern
With a height of 204 metres above
sea level the pylons of the Øresund
Bridge are the tallest concrete
structures in Sweden. The construction
of the pylons began with the placing of
the pylon caissons which had been
cast in a dry dock in Malmö Harbour
and towed to the bridge line. On top of
the caissons the casting of the pylons
was carried out by means of selfclimbing
formwork. The entire casting
process took seven to ten days for
each 4 metre lift.
About 4,335 m 3 of concrete went
into each pylon leg – 220 m 3 per lift in
the first stage and about 34 m 3 per lift
near the top. The concrete was
provided from a batching plant on a
barge moored next to the pylon
cofferdam. Each pylon leg required 800
tonnes of reinforcement which was
prepared in prefabricated cages, and
then lifted into position. The pentagon
shaped pylon legs are solid for the first
17 metres and hollow above that level.
The reinforcement cages for the
cross beams, which connect the pylon
legs approximately 45 metres above
sea level, were built ashore, then lifted
into position for casting. Steel anchor
boxes were also cast into the pylon
legs, to which the cables are attached.
The eight bridge girders for the high
bridge were produced at Karlskrona
shipyard on the East coast of Sweden
and then towed to Malmö, where the
concrete motorway deck was added.
The forty-nine girders for the two
Main contractors on the
Øresund Bridge
Dredging and Reclamation
Öresund Marine Joint Venture:
● Per Aarselff (DK)
● Ballast Nedam Dredging (NL)
● Great Lakes Dredge and Dock
Co. (USA)
The Tunnel
Øresund Tunnel Contractors:
● NCC International (SE)
● Dumez-GTM International (F)
● John Laing (UK)
● E. Pihl & Søn (DK)
● Boskalis Westminster Dredging
(NL)
The Bridge
Sundlink Contractors:
● Skanska (SE)
● Højgaard & Schultz (DK)
● Monberg & Thorsen (DK)
● Hochtief (D)
The Railway
Banverket Industridivisionen (SE)