"Infrastructure madman" is new!
One bridge wins three best in the world
The Fuxia High-speed Rail Quanzhou Bay Bridge has a total length of 20.3 kilometers and a main span of 400 meters. It is the first high-speed rail sea-crossing bridge at home and abroad. It has a design speed of 350 kilometers per hour, the highest in the world. It is the world's first large-scale sea-crossing project using coating-free weathering steel.
On September 15, another milestone project in the field of bridges in the world-the main tower of Quanzhou Bay Bridge on the Fuzhou-Xiamen (Men) high-speed railway was officially topped off.
"Fuzhou-Xiamen High-speed Rail Quanzhou Bay Bridge has a total length of 20.3 kilometers and a main span of 400 meters. The design and construction faces a number of technical challenges. The topping of the main tower of the bridge marks the beginning of the world's high-speed rail sea-crossing era in China's bridge construction." China Railway Construction Fourth Said Zeng Jiahua, the person in charge of the design of the Quanzhou Bay Cross-sea Bridge of the Fuzhou-Xiamen High-speed Railway at the Survey and Design Institute Group Co., Ltd. (hereinafter referred to as the Fourth Railway Institute).
The Fuzhou-Xiamen High-speed Railway Quanzhou Bay Cross-sea Bridge is the first high-speed railway cable-stayed bridge at home and abroad; it is designed to travel at more than 300 kilometers per hour and is the world’s highest and the world’s fourth longest cross-sea railway bridge. It is also the world’s first main tower with coating-free weather resistance Large-scale steel cross-sea project.
High-speed and wind-resistant driving, also ensure that the coin does not fall
The Quanzhou Bay Bridge is a key control project of the Fuxia High-speed Railway. The bridge spans the central waters of Quanzhou Bay and is the world's first high-speed railway sea-crossing bridge.
"The key to the design of a cross-sea high-speed rail bridge is to resist wind and maintain high-speed driving, otherwise the bridge will cause severe lateral shaking and vertical vibration amplitude (vortex shock) due to wind." Zeng Jiahua said.
Geographical and meteorological information shows that Quanzhou Bay is located in the coastal high wind speed belt, with high wind speeds and complex wind conditions. The number of wind days of level 6 and above reaches 91 days throughout the year.
In order to ensure the stability of the bridge in strong winds and maintain the continuity of the high-speed operation of the high-speed trains, the technical team of the Fourth Railway Institute adopted a large number of new structures and new technologies in the design, so that the high-speed trains can operate under a level 8 wind without wind barriers. There is no speed limit when driving at a speed of 350 kilometers per hour, and traffic is not closed under a magnitude 11 storm.
Due to the busy shipping in Quanzhou Bay, the main span must be enlarged to cross the main channel.
"The main bridge of the navigation channel is designed as a cable-stayed bridge with double-tower steel-concrete beams with a main span of 400 meters. The approach bridge in the deep water area on both sides is about 4.3 kilometers long. It adopts a 3-70 meters unsupported monolithic rigid frame bridge. Cable-stayed bridge for the first time." Zeng Jiahua said.
In order to solve the technical problems of passing high-speed railway trains on the long and large sea-crossing bridge under strong wind conditions, the Fourth Railway Institute also made an innovative design for the shape of the bridge's main tower.
"The main girder adopts a streamlined box structure, and effective aerodynamic measures such as baffles, vibration damping railings, and cable eddy current dampers are added." Zeng Jiahua said that these structural designs make the bridge body bypass the wind direction and reduce complex wind The wind-induced vibration in the environment avoids the abnormal vortex vibration that has occurred in domestic bridges such as the Humen Bridge and the Wuhan Parrot Island Yangtze River Bridge.
According to the series of wind tunnel tests and wind-vehicle-line-bridge coupled vibration and other special research results, the Quanzhou Bay Cross-sea Bridge of Fuxia High-speed Rail can withstand strong typhoons of level 12, and the amplitude of vortex-induced vibration is controlled within an astonishing 5 mm.
"This number of vortex vibrations enables high-speed trains to reach the same driving conditions as the land approach bridge even if they pass through the deck of the sea-crossing bridge in a strong wind of level 8, and they can also keep the coins from falling." Zeng Jiahua said.
The adoption of new structures and new technologies has enabled the main line of the Fuxia high-speed rail to reach the operating target of 350 kilometers per hour, eliminating the previous problem of speed reduction of coastal high-speed rail crossing the sea.
Use rust to make rust, adapt to high salt and high humidity corrosion environment
In addition to wind resistance, how to ensure the long-term corrosion resistance and durability of the high-speed railway cross-sea bridge in the marine climate with high salt and high humidity and corrosion?
This is another problem that the design faces.
"In order to solve the problem of bridge corrosion in the marine environment, the previous protection needs to be regularly removed and painted." Zeng Jiahua said that in response to the corrosion problem of important bridge structures in the marine environment, the steel anchor beams and bearings of the pylons of the Quanzhou Bay Bridge on the Fuxia High-speed Railway Innovative use of new materials, the first domestic use of marine atmospheric corrosion-resistant steel, coating-free (no paint), no dehumidification system, the world's first large-scale cross-sea project using coating-free weathering steel, adapted to high salt and high humidity The ocean corrodes the atmosphere.
Weathering steel, that is, atmospheric corrosion-resistant steel, is made of ordinary carbon steel with a small amount of corrosion-resistant elements such as copper and nickel. After incorporating modern metallurgical new mechanisms, new technologies and new processes, it has continued to develop and innovate, and is at the forefront of world super steel technology. One of the series of steel grades.
In order to fill the gaps in the steel grades of my country's marine atmospheric corrosion resistant steel, the design team of the Fourth Railway Institute and Ansteel Group Co., Ltd. (hereinafter referred to as Ansteel Group) set up a project to tackle key problems.
"Through repeated design comparison and selection of steel chemical composition, mechanical and process verification test, marine environment field coupon exposure test, etc., successfully developed nickel-based marine atmospheric corrosion resistant steel, supporting high-strength bolts and welding materials, based on the compactness of the steel itself. The stable passivation rust layer prevents the penetration of chloride ions." Zeng Jiahua said that the project results embody the concept of "rusting with rust" and achieve long-term anti-corrosion effects for the entire life of the bridge in the marine environment.
The technical staff of Anshan Iron and Steel Group and the Fourth Railway Institute said that the Fuxia High-speed Rail Quanzhou Bay Cross-sea Bridge project broke the world technology pattern in which coating-free weathering steel can only be used in ordinary atmospheric environments and coastal environments (above 1 km from the coastline). The development of weathering steel bridges in the world has realized the green full-life design of "paint-free, green durability, and rusty beauty".
Weathering steel has a high cost and can only be used on the most important load-bearing structural components. How can large-area steel beams achieve durability and corrosion protection?
In order to find ultra-long-lasting anti-corrosion coatings for the bridge, the Fourth Railway Institute and the Beijing Institute of Aeronautical Materials have developed and applied an ultra-long and durable anti-corrosion coating system for steel beams.
"The system uses graphene nano-materials modified scale-type alcohol-soluble inorganic zinc-rich primer and super weather-resistant fluorocarbon topcoat. The salt spray resistance and artificial accelerated aging resistance are more than twice that of the prior art. It can realize steel structure The goal of ultra-long life and durability of more than 30 years in the marine corrosive atmosphere." Zeng Jiahua said, this time is higher than the current design anti-corrosion life of the longest 25 years of sea-crossing bridges, and will realize the 30-year ultra-long anti-corrosion coating system of steel beams in China Technical breakthrough in anti-corrosion life.
Long-connected large-span, millimeter-level precision built for strong earthquake
The full joint length of the Fuxia High-speed Railway Quanzhou Bay Bridge is designed with steel-concrete composite beams, which is the first use of cable-stayed railway bridges at home and abroad.
All the components are manufactured in factories, and the approach bridge in the deep water area adopts a standardized unsupported integral prestressed concrete rigid frame bridge.
"Through the design and selection of the above-mentioned bridge structure forms and systems, the millimeter-level construction accuracy requirements of high-speed railway bridges have been achieved." Zeng Jiahua said.
The Fuzhou-Xiamen high-speed railway is designed to be located in the coastal area of Fujian and the west bank of the Taiwan Strait, starting from Fuzhou in the north, passing through Putian, Quanzhou, Xiamen, and reaching Zhangzhou in the south. The main line is 277 kilometers long and the designed speed is 350 kilometers. The high-speed railway project in service under the ocean environment, the coastal/cross-sea railway with the highest speed at home and abroad.
"The Quanzhou Bay High-speed Rail Cross-sea Bridge is located on the west bank of the Taiwan Strait. It is an area of high seismic intensity and has the possibility of a magnitude 8 earthquake." Zeng Jiahua said.
How to solve the seismic design problem of the long-linked high-pier cross-sea bridge?
"The design team developed a comprehensive seismic isolation system and technology using longitudinal viscous dampers, shearable weather-resistant hyperboloid spherical steel bearings, and metal dampers; using a non-supported monolithic rigid frame bridge to realize a long-connected high-pier bridge The system of flexible high piers and girder parts coordinated to bear the force, which solves the seismic design problem of long-connected high piers and large-span bridges in high seismic intensity areas." Zeng Jiahua said.
In addition to the continuous innovation of structural design technology and materials, the design of the Quanzhou Bay Bridge on the Fuxia High-speed Railway also fully implements the modern concept of "exquisite engineering, intelligent engineering and environmentally friendly engineering", that is, a good architectural design must be integrated into the local natural environment.
“The project has carried out a landscape thematic design in cooperation with the Academy of Fine Arts, fully integrating marine elements. The bridge tower adopts a shell-shaped curved bridge tower, which takes into account the reasonable structure and architectural aesthetics.” Zeng Jiahua explained that the design implies that “Quanzhou is the first economy in Fujian. A strong city, the starting point of the ancient Maritime Silk Road and the largest port in the Orient at that time", the ocean gave birth to the coastal city of Quanzhou, giving her endless vitality and development impetus. It will be the development of the Maritime Silk Road in the 21st century. Under the opportunity, set sail to reproduce the glory of maritime trade and the world's largest port.
Experts believe that the Fuxia High-speed Rail Quanzhou Bay Cross-sea Bridge will promote the technological development of large-span high-speed railways and cross-sea bridges in China. It will become one of the representative projects of China's high-speed railway version 2.0 and will also be a milestone project in the field of bridges in the world.