The longest bridge in the world

The Lake Pontchartrain Bridge is the world's longest continuous bridge over water, measuring 24.5 miles (38.35 km) and containing approximately 9,500 concrete piers.

The Lake Pontchartrain Bridge is 24.5 miles long. Photo: Mark Runde

During the 1940s and 1950s, New Orleans, Louisiana, was booming, but access to the city was blocked by a lake. Driving to New Orleans from the north shore was a long and time-consuming process. Therefore, the Greater New Orleans Highway Commission was formed to build the Lake Pontchartrain Bridge.

The bridge was a huge success, benefiting residents on both sides of the lake by significantly reducing travel times. It also provided access for New Orleans tourists to visit restaurants and retail stores on the north shore.

The Lake Pontchartrain Bridge is actually two parallel bridges. The two-lane southbound bridge first opened on August 30, 1956, while the similarly designed northbound bridge was completed in 1969. Despite its massive size, the bridge was built in just 14 months using assembly line and mass production methods. In fact, it was the first time these construction methods had been used on a bridge.

The southbound bridge has 2,246 spans, approximately 8.5 m wide and 17 m long, while the northbound bridge has 1,506 spans, 8.5 m wide and 25.6 m long. The spans consist of precast reinforced concrete girders (all components are cast together simultaneously), railings and decks. The spans on both the northbound and southbound bridges are supported by precast concrete piers averaging 27.4 m in length.

When it opened, the Lake Pontchartrain Bridge held the Guinness World Record for the world's longest bridge over water, but that title was challenged in 2011 when the 41.58 km Qingdao Jiaozhou Bay Bridge opened in China. The controversy surrounding the two bridges led Guinness World Records to create two separate categories. The Lake Pontchartrain Bridge became the world's longest continuous bridge over water, while the Qingdao Jiaozhou Bay Bridge became the longest composite bridge.

Sea-crossing bridge sets 10 world records
China's mega project holds a series of world records, shortening travel time between Shenzhen and Zhongshan from 2 hours to 30 minutes.

Artificial island of Shenzhen-Zhongshan sea bridge project. Photo: Xinhua

Last weekend, China opened the Shenzhen-Zhongshan Bridge-Tunnel project in Guangdong province. This engineering marvel broke 10 world records when it was inaugurated, New Atlas reported on July 1.

The Pearl River estuary, where it flows into the South China Sea, is one of the most densely populated areas in the world. It includes Hong Kong, Macao and nine cities in Guangdong, separated by a vast expanse of water, making travel difficult. The Shenzhen-Zhongshan project was designed to overcome that disadvantage. The 24-kilometer-long structure connects two cities on opposite sides of the Pearl River estuary. However, it is not a long bridge, but a tunnel runs between two artificial islands, with bridges connecting each island to the city on the same side.

With eight lanes and a maximum speed of 100 km/h, the new route shortens driving time from two hours to 30 minutes. After seven years of construction, the project opened to traffic at 3 p.m. on June 30 local time. According to CGTN, the Shenzhen-Zhongshan project set 10 world records, including the highest bridge deck (91 m), the highest clearance for a sea bridge, the largest offshore suspension bridge anchor (344,000 m3 of concrete), the highest wind resistance test speed for a suspension bridge (83.7 m/s), the largest steel bridge deck paved with hot-mixed epoxy asphalt (378,800 m2), the longest 8-lane two-way submerged tube tunnel, the widest underwater steel-shelled concrete submerged tube tunnel (55.6 m), the largest casting volume for a steel-shelled submerged tube using self-compacting concrete (29,000 m3/tube section), and the widest foldable M-shaped waterstop used in the final joint of a submerged tube tunnel (3 m).

On top of that, the tunnel has some interesting safety features, including a new fire suppression system. A team of 14 robots patrol the tunnel regularly, monitoring pipes and cables to keep things running smoothly, even keeping an eye out for car accidents. When that happens, they can direct traffic through built-in speakers, record footage, and stream it to a remote control center.

The lights along the tunnel walls also use a color-coded system. When everything is okay, the lights are green, but in an emergency, they turn red. The lights can even change from yellow to green along the length of the tunnel, guiding people in the right direction when it is time to evacuate.

The Shenzhen-Zhongshan project connects with the Hong Kong-Zhuhai-Macau Bridge, the world's longest sea-crossing bridge, 31 km away, making it easier for people to travel around these densely populated areas.