Mozhai Wujiang River Bridge is under construction. (Photo/CRCC Harbour & Channel Engineering Bureau Group)

After intricately threading cables, ranging from several to tens of tons, in the sky two to three hundred meters above the ground, the Mozhai Wujiang River Bridge's cable-bent tower was capped at 320 meters above the water in Southwest China's Chongqing on Jan 3. This marked the topping-out of the main tower of Asia's tallest low-pylon cable-stayed bridge.

The 708-meter-long bridge is slated to open to traffic in late June 2024, with its No.3 pier reaching 216 meters, the tallest of its kind in Asia.

The bridge is sandwiched between two mountains, spanning across the Wujiang River. At the project's initiation, the bridge site on a nearly vertical cliff lacked construction access and made onshore road construction impossible.

To overcome terrain and space limitations, the construction team built a 247-meter-long, 9-meter-wide steel landing stage spanning the Wujiang River in 8 months. It serves for transporting construction personnel and materials.

"All the materials needed for the construction of the landing stage were transported by barges," said Zhai Shuisheng, deputy chief engineer of the project with CRCC Harbour & Channel Engineering Bureau Group.

Beyond the steep terrain, the bridge features ultra-high piers and a cross-section over 520 square meters—three times that of a typical bridge. These challenges led the team to deploy intelligent devices and technologies.

They used a fully intelligent temperature control system to prevent winter concrete cracking and employed smart monitoring for real-time tracking of conditions in various parts of the bridge and the construction scene, for example.

The stay cables, often referred to as the "lifeline" of the cable-stayed bridge, play a crucial role in connecting the main beams and the main towers. Each bridge tower is equipped with 21 pairs of stay cables, with each pair consisting of 73 high-strength epoxy-coated steel strands ranging from 85.5 meters to 267 meters in length and weighing between 7.7 tons and 24 tons.

During construction, workers used threading machines and winches to thread stay cables through cable-bent towers at the height of hundreds of meters, resembling "threading a needle."

The bridge construction is progressing smoothly, with full closure expected by May, according to CRCC Chongqing Investment Group.

(Liu Meihui, as an intern, also contributed to this report.)