The longest concrete arch bridge in the world

According to Interesting Engineering, the Tian'e Longtan Bridge in China's Guangxi province has set a new standard for concrete arch bridges - a type of bridge with curved load-bearing parts to transmit loads from the bridge deck to the two ends of the arch, and from there to the ground or bridge abutments. The 600 m bridge span has been researched before, but this is the first time it has been implemented in practice.

According to Xinhua, the bridge has a total length of nearly 2,500 m with four lanes of traffic in two directions, put into use in 2024, and is currently recognized as the largest concrete span bridge in the world.

The biggest challenge when building a long bridge span lies in the mass that the large concrete arch structure must bear, of which more than 90% of the load comes from the bridge's own weight. Therefore, engineers changed the arch design to reduce the amount of concrete needed. They divided the main arch into two parallel lines and identified areas that did not have to carry as much force and reduced the material there instead of making the entire arch equally thick and dense.

Thanks to design innovation, the width of the arch system is reduced from 23 meters to 13 meters. The volume of concrete used decreased from about 40,000 m³ to 28,000 m³. Compared to bridges with spans of about 400 m, the new design cuts about 22% of concrete per meter of length, while maintaining the same load-bearing capacity.

The arch bridge option also offers economic advantages compared to cable-stayed bridges - the bridge deck is directly supported by cables connected to one or more bridge towers. According to Stdaily, this design has helped save about 16.37 million USD in construction costs. In addition, over the project's expected lifespan of 100 years, the maintenance cost of the concrete arch bridge will be $65.9 million lower than the alternative.

During construction in 2023, the International Association of Bridge and Structural Engineering (IABSE) rated the bridge's technology as "world class". At the end of August, the project continued to win the top prize at the Guangxi Provincial Science and Technology Awards, recognizing technical achievements that help concrete arch bridge construction technology surpass previous limits.

The two previous records also belonged to China with the Beipan River Bridge, span 445 m and Yangtze River Bridge, span 420 m. Some other large-span concrete arch bridges include Crotia's Krk bridge with a span of 390 m, Spain's Almonte Railway bridge with a span of 384 m.

Nam Nguyen