Viaduc de Millau - Longest Cable-stayed Bridge in the World | Génie Français - Megabridges Ep.1

Summary

The Mayor Viaduct, a stunning 2,460-meter-long bridge in southern France, solved severe traffic congestion in the town of Mayor. Completed in just three years, it was designed by Lord Norman Foster and engineered by Michelle Viele. The viaduct features seven towering pylons, innovative wind-resistant design, and a unique system to move the road deck across the valley. Advanced engineering solutions ensured the viaduct’s stability, even with extreme weather conditions. The project’s success is a testament to human ingenuity, blending both functional and aesthetic features to create a remarkable feat of modern infrastructure.

Takeaways

• 😀 The Mayor Viaduct is a colossal engineering feat, stretching 2,460 meters and supported by the tallest pylons ever erected, with a total weight of 290,000 tons.
• 😀 The construction of the viaduct began in 2001, aiming to alleviate severe traffic congestion in the small town of Mayor, France, which was a major bottleneck for travelers.
• 😀 The project was designed by British architect Norman Foster and managed by bridge expert Michel Viel, known for his previous work on the Normandy and Sultan Selim bridges.
• 😀 One of the biggest challenges in building the viaduct was creating stable foundations in the steep and rocky terrain of the Mayor Valley, requiring the installation of deep well shafts for support.
• 😀 The pylons of the viaduct were constructed using a technique that involved pouring concrete in successive slices, allowing for rapid construction with each pylon rising four meters every three days.
• 😀 The viaduct's pylons vary in height, with some reaching up to 245 meters, and were split near the top to reduce wind pressure and enhance the structure's durability.
• 😀 The project faced significant challenges from the strong winds in the region, with winds exceeding 100 km/h; the pylons were designed to withstand these forces by allowing them to flex and move.
• 😀 A key technological innovation was the use of 'translators,' hoist systems that allowed the road deck to be pushed across the valley and onto the pylons, moving it in 60-centimeter increments.
• 😀 To reduce risk during construction, temporary towers were used to support the road deck while it was moved into position, and precise synchronization ensured the safe advancement of the deck over 171-meter spans.
• 😀 After 15 months of painstaking work, the two halves of the road deck were joined together, marking a significant milestone in the project’s completion.
• 😀 The viaduct was designed with aerodynamics in mind, ensuring the deck could withstand wind speeds up to 150 km/h, with built-in systems to prevent rust and manage the expansion and contraction caused by temperature changes.

Q & A

What was the main reason for the construction of the Mayor Viaduct?

The Mayor Viaduct was constructed to alleviate the severe traffic jams that occurred in the town of Mayor, France, particularly during the summer. The town's narrow streets caused bottlenecks, making it difficult for vehicles to pass, leading to significant delays and hindering economic development.

Who designed the Mayor Viaduct and who was in charge of the construction?

The Mayor Viaduct was designed by British architect Lord Norman Foster. The construction project was led by Michelle Vielle, a renowned specialist in bridges and viaducts, who had worked on projects like the Normandy Bridge and the Sultan Selin Bridge in Istanbul.

What were some of the challenges faced during the construction of the Mayor Viaduct?

The construction faced several challenges, including the difficult terrain of the valley, high wind speeds in the region, the enormous size of the viaduct, and the need to move a 36,000-ton road deck over a 200-meter void. Additionally, ensuring the structural integrity of the viaduct and managing the construction of seven massive pylons were major hurdles.

Why was the substructure of the viaduct so critical to its success?

The substructure was essential because the valley was steep and uneven. To ensure stability, vertical tubes (similar to well shafts) were dug into the rock, providing a strong foundation for each of the seven pylons, allowing the viaduct to support the tremendous weight of the road deck and pylons.

How were the pylons constructed, and what unique technique was used?

The pylons were built using a technique that involved pouring concrete in successive slices, each four meters high. A mobile framework was used to mold the concrete, which was then lifted using rails inside the shafts. This allowed the pylons to rise quickly, with new slices added every three days.

What role did wind play in the design of the viaduct's pylons?

The pylons were designed with splits in their upper parts to reduce the impact of high winds. This design allowed the wind to pass through, lessening its force on the pylons and enhancing their durability. Wind in the region can reach speeds of over 100 km/h, so this feature was crucial for the viaduct's stability.

How was the road deck moved over the valley during construction?

The road deck was moved using a unique system of translators, which are hoists that gradually advanced the deck from one support to the next. This process was extremely precise, with the deck being moved forward by 60 centimeters at a time, eventually covering a distance of 171 meters between supports.

What technology was used to ensure the accurate movement of the road deck?

Dozens of computers worked in coordination to synchronize the movement of the translators, ensuring that the road deck advanced evenly and consistently. Lasers were used to monitor the position of the pylons and towers, ensuring that the deck remained on course during the delicate process.

What steps were taken to ensure the durability of the viaduct over time?

To ensure durability, the viaduct was designed to withstand strong winds and temperature changes. Special joints were placed at both ends of the bridge to accommodate thermal expansion, and the road deck was coated with a dehumidification system to prevent rust. Additionally, the viaduct's steel structure was carefully protected against corrosion.

What visual effect did the designers create to enhance the experience of crossing the viaduct?

The designers incorporated a slight curve into the viaduct's design, allowing drivers to see the pylons one after another as they cross. This visual effect creates a sense of progression and emphasizes the scale of the structure, making the experience of crossing the town valley even more impressive.