On the morning of January 24, amid the vast blue waves of the East China Sea, as a 70-meter box girder weighing over 1,800 tons was slowly lowered by a large offshore floating crane onto the high pier at the north side span of the main navigation opening of the Zhoudai Bridge, the main channel project of Ningbo-Zhoushan Port achieved its main line breakthrough.

　　Full line to open to traffic by end of 2021

　　The Ningbo-Zhoushan Port main channel project in Zhejiang, led and invested in by Zhejiang Provincial Communications Group, has a total length of 36.78 kilometers and a total investment of approximately 16.3 billion yuan. It connects five islands in Zhoushan, Zhejiang—Fuchi Island, Zhoushan Main Island, Changbai Island, Daishan Island, and Yushan Island—and crosses five navigation channels. It is designed to a two-way, four-lane expressway standard and is scheduled to be fully completed and opened to traffic by the end of 2021. Among its components, the Yushan Bridge and the Fuchimen Bridge were completed and opened to traffic in 2018 and 2019, respectively.

　　Dubbed by the industry as a super transport project after the Hong Kong-Zhuhai-Macao Bridge, the project will connect with the Yongzhou Expressway upon completion, span eight islands, and feature ten major bridges, running north all the way to Shanghai. It will become the world's longest island-linking expressway and the largest cluster of sea-crossing bridges, creating the shortest land transport route among Shanghai, Ningbo, and Zhoushan. It is of great significance for improving the regional comprehensive transport network, supporting industrial layout planning, and advancing the integrated development of the Yangtze River Delta.

　　A responsible person from the Main Channel Project Construction Command of Zhejiang Provincial Communications Group introduced that the Zhoudai Bridge is an important component of the Shanghai-Zhoushan-Ningbo sea-crossing corridor. After the main line breakthrough of the bridge, the project will gradually shift to bridge deck construction, including pavement works, building construction works, and traffic safety works.

　　As of now, the overall image progress of the Ningbo-Zhoushan Port main channel project has reached 92%, of which the cumulative image progress of the Zhoudai Bridge has reached 89%.

　　Creating China's heaviest and longest sea-crossing box girder

　　The Zhoudai Bridge has a total of 370 box girders, each 70 meters long and weighing 1,854 tons, making them the heaviest and longest concrete box girders among sea-crossing bridges currently under construction in China.

　　To ensure that box girder production meets the overall schedule requirements of the Zhoudai Bridge, the project department set up two box girder production lines and built six sets of rebar cage tying jigs, six sets of stainless steel box girder external formwork, and six sets of fully hydraulic internal formwork.

　　During this period, to ensure the safety, quality, and progress of precast box girders, the project department added two truck cranes and two sets of 70-meter hydraulic new internal formwork starting in the first half of 2019. Meanwhile, the number of workers in the box girder area of the precast yard increased from more than 210 to more than 360, enabling production of up to 24 box girders per month during peak periods.

　　To enable these "giants" to move freely from the casting pedestals to the storage pedestals and, after the curing period, to be smoothly transferred from the storage pedestals to transport vessels at the sea access wharf, the project department also specially built two 1,200-ton girder lifting and transporting machines for these "big guys." It is worth mentioning that this girder lifting and transporting machine has also been certified by the Shanghai Great World Guinness headquarters as "China's largest tire-type crane."

　　"During the erection of a box girder, it mainly needs to go through three arduous tasks: moving the girder and loading it onto a vessel within the precast yard, sea transport, and erection at the pier position," said a responsible person from China Railway Major Bridge Engineering Group, the project contractor. To safely and precisely erect the box girders onto the tall piers, the project department improved the existing crane vessels and lifting devices through meticulous scientific calculations and repeated expert demonstrations, used a large offshore floating crane with a maximum lifting capacity of 2,600 tons, and independently developed a self-balancing box girder lifting device, helping box girder erection enter the fast lane.