Recently, the first main girder of the Wenzhou Oujiang North Estuary Bridge was successfully erected. The Wenzhou Oujiang North Estuary Bridge is the final section of China's coastal artery, the Yongguan Expressway, and is scheduled to be closed and completed by the end of the year. After the bridge officially opens to traffic, the approximately 645-kilometer Yongguan Expressway will be fully completed, and the cross-river journey from Yueqing to Longwan in Wenzhou will be shortened from more than one hour to just 15 minutes.

It is understood that the Wenzhou Oujiang North Estuary Bridge is the world's first three-tower four-span double-deck steel truss suspension bridge, with the upper deck carrying the Yongguan Expressway and the lower deck carrying National Highway G228. The bridge has a total length of 7.9 kilometers, of which the main bridge crossing the Oujiang River is 2,090 meters long. It is currently one of the bridges with the greatest technical difficulty and the most complex construction technology in China and even the world.

"Two Bridges Built as One" Upholds the Concept of Green and Intensive Development

The Oujiang North Estuary Bridge vigorously promotes the application of steel structures, with steel consumption for the entire bridge reaching more than 300,000 tons. The main girder is entirely of steel structure, effectively enhancing the bridge's construction quality and achieving green and intensive development.

As one of the first batch of green highway demonstration projects of the Ministry of Transport, the North Estuary Bridge incorporates the green concepts of "resource conservation, ecological environmental protection, and social recognition" into its construction. The project adopts a collinear design with a double-deck deck system, and the main bridge is a steel truss structure with a double-deck deck, realizing intensive development of corridor and shoreline resources and saving about 193 mu of land. "Compared with concrete bridges, steel structures have advantages such as lighter self-weight, uniform materials, stable quality, factory manufacturing, prefabricated construction, and a high degree of recyclability, and are more energy-saving and environmentally friendly," introduced Zheng Fengli, Deputy General Manager and Chief Engineer of Wenzhou Transportation Development Group.

"Bridge Experts" Safeguard Main Girder Construction

The hydrological conditions in the construction waters of the project are complex, with rapid currents and a maximum tidal range of 5.35 meters, making it extremely difficult for construction vessels to anchor and position. Moreover, as the first three-tower four-span double-deck steel truss suspension bridge, the synchronization and matching requirements for the hoisting of the four-span main girder are extremely high, greatly increasing the construction difficulty of main girder hoisting. To this end, the project integrated well-known domestic design, supervision, construction, monitoring, manufacturing, equipment, and transportation units one year in advance to prepare a detailed construction plan, and established an expert group headed by the former Chief Engineer of the Ministry of Transport and the President of the World Bridge Association to review the plan. At the same time, Southwest Jiaotong University and Southeast University were commissioned to carry out relevant special studies to ensure the safety and reliability of the construction plan.

"Powerful National Equipment" Helps Scale the Peaks of Bridge Construction

The bridge project has a novel and unique structure, and the main girder construction technology is complex. The 2-kilometer hoisting range is divided into 9 construction zones, involving 9 different construction techniques such as swing shifting, direct lifting, and cable-mounted cranes. In particular, the cable-girder intersection section, designed for the first time due to aviation height restrictions at mid-span, adopts a relay hoisting technique of cable-mounted crane plus direct lifting, which is the first of its kind in China. In addition, navigation in the bridge site area is busy, and 110 girder segments need to be installed intensively. The construction difficulty, special working conditions, and technological complexity are unprecedented in China.

"The maximum segment weight of the main girder reaches 813 tons, and existing domestic cable-mounted cranes cannot meet the lifting requirements of a single unit," introduced Pan Ji, General Manager of Wenzhou Oujiang Estuary Bridge Company. To solve the challenge of building one of the world's "most difficult bridges to construct," the project innovatively developed China's first 1,000-ton-class cable-mounted crane, equipped with technologies such as human-machine interfaces, sensor technology, and communication technology, controlling the installation accuracy error within 5 millimeters and ensuring safe and efficient construction.

Since the "13th Five-Year Plan," Wenzhou has set off a wave of "vigorously developing transportation and developing major transportation." The city's comprehensive transportation investment has exceeded 200 billion yuan, doubling that of the "12th Five-Year Plan" period. The city's total highway mileage has jumped from third from the bottom in the province to second in the province, and "sea, land, air, and rail" have achieved qualitative leaps. In the "14th Five-Year Plan," Wenzhou will make every effort to advance the implementation of key comprehensive transportation projects, comprehensively improve the integrated development level of corridors, hubs, and networks, and basically build a national comprehensive transportation hub. The Wenzhou Oujiang North Estuary Bridge, a major national transportation project to be completed during the "14th Five-Year Plan" period, will greatly boost Wenzhou's development across the Oujiang River and along the river.