2. The Millau Viaduct is a cable-stayed
bridge that spans the valley of the River
Tarn near Millau in southern France .
It is the 12th highest bridge deck in the
world.
It was built to reduce traffic of small
town Millau as the motorway
connecting Paris and Spain passed
through Millau.
INTRODUCTION
The Millau Viaduct is a cable-stayed
bridge that spans the valley of the River
Tarn near Millau in southern France .
It is the 12th highest bridge deck in the
world.
It was built to reduce traffic of small town
Millau as the motorway connecting Paris
and Spain passed through Millau.
3. MAJOR ENGINEERING
CHALLENGES
1) BUILD THE TALLEST BRIDGE PIERS IN THE
WORLD.
2) PUT 36000TON FREEWAY ON TOP OF IT.
3) ERECT 7 STEEL PYLONS HUNDREDS OF
METER ABOVE THE SOLID GROUND.
4. SPECIFICATIONS
MILLAU VIADUCT
Crosses : River Tarn
Design : Cable-stayed bridge
Total length : 2.5 km long
Width : 32 m
Longest span : 342 m
Highest pier : 245 m
Curved radius : constant 20 km
6. Each pier is treated as a worksite in its
own right so that construction of all the
seven bridges can take place
independently.
The geometry of the piers varies from
one pouring step to the following
pouring step and is tapering entire way
up.
7. The shape of the mould was changed at
every 4m height to fit the profile and
reinforcing concrete method was used
in raising the pier.
The formwork was of self-climbing type
for outer surfaces and craneassisted for
the inner surfaces as the risk factor was
to be taken care of.
Altimetric checks by GPS ensured a
precision of the order of 5mm in both X
and Y direction.
8. • The installation of the deck by
successive launching
operations requires the
erection of 7 temporary piers.
• These piers consists of a
metal framework of a square
section of 12mx12m whose
members are tubes of
1,016mm diameter.
• They introduced this piers
between the two pillers as
the span between the two
piers was large and deck
could not support itself.
Temporary piers
9. Steel Decks
They opted for steel deck
over the conventional concrete
block,as it is not economical
and safe to lift concrete over
such heights.
Fabrication of the deck
section was done on steel
factory .
Around 2200 sections each
weighing upto 90 tonnes and
were some were 22 long.
10. Launching the deck
7 temporary piers help
support the weight of
the deck,as the longest
deck could support was
half the span.
Two deck segments
were launched from
each end of the bridge
11. Hydraulic launchers
•Computerized launchers
push the pre-fabricated deck
segments on to the piers.
•Each cycle moves the deck
600 mm.
• Total of 5000 cycles
required.
•The cycle is repeated every
4 minutes
12.
13.
14. NOSE RECOVERY
•Weight of steel box girder
deck sags as span is
completed.
•Nose recovery system
attached to raise the deck to
the level of the next pier.
•This aligns the deck for the
level and curvature of the next
pier.
•The precision carried out in
the nose recovery system was
due to the use of GPS system
as the accuracy was upto
4mm.
16. After the deck construction was finished it
was time to erect the pylons to provide cable
support for the bridge.
The temporary piers were supporting the
deck but due to the flexibility of the steel the
deck was very undulating, the deformations
were quite large.
So the 90 m tall and 700 ton pylons were
installed as fast as possible.
The pylons and cables were needed to
straighten the undulated deck.
17. For placing the pylons steel engineer Marc
Buonomo used a technique which was
practiced in the ancient Egypt.
In this Egyptian method the pylons were
lifted slowly using a hydraulic machine.
As they were being lifted they were also
made to pivot by two temporary steel
towers,both of them secured by a cable.
As the bridge is lifted it also pivots untill it
is vertical and it is erected .
18. Connection between pylon , deck
and the pier
An inverted Y shape ha
been adopted for the
pylons,which are metal,and
which are oriented
longitudinally as extensions
of the split shafts of the
piers.
This arrangement gives
the pylons the required high
degree of rigidity.
20. With all seven pylons in place it was time to
attach the cables stays that would straighten the
rippling deck and give it the strength to endure
the traffic load.
The roadway weighs over 40000 tonnes and
the 154 cable stays should prevent it from
sagging or collapsing.
These cable stays are made of 91 individual
steel strands and have breaking strength of
25000 tonnes.
These stays are strong enough to hold 25
jumbo jets all at full throttle!
21.
22. An issue that presented itself after the bridge
was completed was the fact that the wind
speed at the level of the bridge was “upto 151
km/hr”,which is significantly more than the
wind speed that would be found at ground
level.
This would cause serious issues driving on the
bridge because the high wind speeds would
push vehicle to the side, making driving
dangerous.
This problem was addressed by the inclusion
of windscreens that reduced the affect of the
“wind by 50%”,effectively causing wind speeds
on the bridge to reflect those on the ground.
23. GRADING OF MATERIALS
The deck and the pylons,entirely of
metal,are made of steel of grade S355 and
S460.
The piers are constructed in B60
concrete.
This concrete was chosen more for its
durability than for its high mechanical
resistance.
