The Millau Viaduct is the tallest cable-stayed bridge in the world, located in southern France. It features 7 pylons up to 343 meters tall that support a 2,460 meter long steel deck. The bridge's longest span is 346 meters and it was constructed between 2001-2004 to shorten travel time across the region.

1. THE MILLAU
VIADUCT
Cable-stayed bridge, @Millau,
France

3. PROJECT DATA
• Location: Millau, France
• Motorway bridge over the river Tarn in Millau and longest cable-
stayed bridge in the world
• construction period: 2001 - 2004
• construction: cable-stayed bridge
• construction method: bridge as a steel box superstructure using
an incremental launching method
• eight-section bridge with a length of 2,460 m
• highest piers: 343 m with steel structure
• seven reinforced concrete piers from approx. 78 m to 245 m
• cross-section change from single to double piers, 90 m below
the superstructure

4. PROJECT DATA
• Total width of span is 32.05m with 2 lanes on both the sides
• Longest span of bridge is 346m long
• Total cost of construction = 400 million euro
• Before construction of bridge ‘Fairy service’ took one & half hour
for crossing, but after construction of bridge this distance is passes
away in 5-10 minutes.
• It’s tallest pier is even taller than Eiffel Tower
• Tallest Pylons in the world

5. STRUCTURAL ELEMENTS
1. PYLONS & ABUTMENTS
~Each pylon is supported by four deep shafts, 15 m
(49 ft) deep and 5 m (16 ft) in diameter.
~The abutments are concrete structures that provide
anchorage for the deck to the ground at corners of
bridge
P1 P2 P3 P4 P5 P6 P7
94.50m 244.9m 221.0m 144.2m 136.4m 111.9m 77.56m

7. 2. DECK
• The metallic deck, which appears very light despite its total
mass of around 36,000 tonnes (40,000 short tons), is 2,460 m
(8,070 ft) long and 32 m (105 ft) wide.
• These are composed of 173 central box beams, the spinal
column of the construction, onto which the lateral floors and
the lateral box beams were welded.
• The central box beams have a 4 m (13 ft) cross-section and a
length of 15–22 m (49–72 ft) for a total weight of 90 metric
tons (99 short tons). The deck has an inverse Airfoil shape,
providing negative lift in strong wind conditions.

8. 3. MASTS
• The seven masts, each
87 m (285 ft) high and
weighing around 700
tonnes (690 long tons; 770
short tons), are set on top of
the pylons. Between each
of them, eleven stays
(metal cables) are
anchored, providing
support for the road deck.

9. 4.STAYS
• Each mast of the viaduct is equipped with a monoaxial layer of
eleven pairs of stays laid face to face. Depending on their length, the
stays were made of 55 to 91 high tensile steel cables, or strands,
themselves formed of seven strands of steel (a central strand with six
intertwined strands).
• Each strand has triple protection against corrosion (galvanisation, a
coating of petroleum wax and an extruded polyethylene sheath).
The exterior envelope of the stays is itself coated along its entire
length with a double helical weatherstrip. The idea is to avoid running
water which, in high winds, could cause vibration in the stays and
compromise the stability of the viaduct.
• The stays were installed by the Freyssinet company.

10. 5. SURFACE
• To allow for deformations of the metal deck under traffic, a special
surface of modified bitumen was installed by research teams
from Appia.
• The surface is somewhat flexible to adapt to deformations in the steel
deck without cracking, but it must nevertheless have sufficient strength
to withstand motorway conditions (fatigue, density, texture,
adherence, anti-rutting etc.).
• The "ideal formula" was found only after two years of research

11. 6. ELECTRICAL
INSTALLATIONS
• The electrical installations of the
viaduct are large in proportion
to the size of the bridge.
• There are 30 km (19 mi) of high-
current cables, 20 km (12 mi)
of fibre optics, 10 km (6.2 mi) of
low-current cables and 357
telephone sockets allowing
maintenance teams to
communicate with each other
and with the command post.
• These are situated on the deck,
on the pylons and on the masts.

12. 7. SAFETY MEASURES
• The pylons, deck, masts and stays are equipped with a multitude of sensors.
These are designed to detect the slightest movement in the viaduct and
measure its resistance to wear-and-tear over
time. Anemometers, accelerometers, inclinometers, temperature sensors are
all used for the instrumentation network.
• Twelve fibre optic extensometers were installed in the base of pylon P2. Being
the tallest of all, it is therefore under the most intense stress. These sensors
detect movements on the order of a micrometre. Other extensometers—
electrical this time—are distributed on top of P2 and P7. This apparatus is
capable of taking up to 100 readings per second. In high winds, they
continuously monitor the reactions of the viaduct to extreme conditions.
Accelerometers placed strategically on the deck monitor the oscillations that
can affect the metal structure. Displacements of the deck on the abutment
level are measured to the nearest millimetre. The stays are also instrumented,
and their ageing meticulously analysed. Additionally, two piezoelectric
sensors gather traffic data: weight of vehicles, average speed, density of the
flow of traffic, etc. This system can distinguish between fourteen different types
of vehicle.
• The data is transmitted by an Ethernet network to a computer in the IT room at
the management building situated near the toll plaza.

13. CONSTRUCTION OVERVIEW
• Temporary piers
used to help launch
and support the deck
as the the pylons
were constructed.
• The 2460m deck was
launched in two
pieces.
• Pylons and cables
were added on top
of the piers.

14. DECK LAUNCHING
• 7 temporary piers help
support the weight of the
deck.
• 2 deck segments are
launched from the each end
of te bhridge.

15. HYDRAULIC LAUNCHERS
• launchers push the pre-
fabricated deck
segments onto the
piers.
• cycle moves the deck
600mm. Total of 5000
cycles required.

16. 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.

17. COMPLETION
• Deck segments move towards each other at the
rate of 0.9 meter per hour.
• Two deck segments joined in May of 2004.

18. PHOTOES OF CONSTRUCTION
Hollow pier construction by moving
formwork with hydraulic crane