Main Span of World’s Longest Three-Tower Steel Box Girder Cable-Stayed Qinglongmen Bridge Seamlessly Closed in Zhejiang
According to Zhejiang Transport News on 23 June, the main bridge of Qinglongmen Extra Large Bridge, recognised as the world’s three-tower steel box girder cable-stayed bridge with the largest single span, has achieved full structural closure. The joint project undertaken by China Railway Construction Bridge Engineering Bureau and China Railway Construction Harbour and Navigation Bureau completes all core main structure works, laying solid groundwork for the scheduled opening of Phase Two of the Liuheng Cross-Sea Highway Bridge serving Ningbo Zhoushan Port in Zhejiang Province.
Spanning the Qinglongmen waterway of Zhoushan in Zhejiang, the crossing links Fodu Island of Zhoushan with Meishan Island of Ningbo. The overall bridge stretches 2,212 metres in total length, engineered as a three-tower, double cable-plane integral steel box girder cable-stayed design, with two equal main spans each measuring 756 metres.
Two separate steel girder segments were hoisted simultaneously to finish the final closure joint. Each segment runs 4.5 metres in length and carries a dead weight of 82.8 tonnes. Construction crews operate within a complex marine environment marked by powerful tidal surges and frequent gales. Wind force level six or above prevails on more than half of all days each year, whilst annual foggy days exceed 40. The water channel beneath the crossing must maintain unobstructed safe passage for container vessels of up to 50,000 deadweight tonnes, leaving only narrow windows for precision lifting works. Ahead of the closure operation, continuous 48-hour real-time environmental monitoring was deployed to calibrate the dimensional tolerance of closure gaps against fluctuating ambient temperatures, enabling millimetre-level accurate alignment and embedding of the girder segments.
Multiple world-class technical bottlenecks have been resolved throughout the construction cycle. Permanent-temporary integrated steel cofferdams are deployed for main pier foundations; these structures function as water-retaining enclosures during construction before serving as permanent anti-collision barriers once the project enters service. During lowering operations, the 2,400-tonne steel cofferdam is positioned over 41 foundation piles with an axial deviation margin capped at 1.5 centimetres. The three main pylons adopt domestically pioneering steel-concrete composite tower technology, allowing modular block assembly at sea in a building-block style. This prefabricated method drastically cuts the duration of high-altitude offshore construction tasks and lowers operational risks exposed to harsh marine weather.
Qinglongmen Extra Large Bridge forms the vital cross-sea artery of the Liuheng Highway Bridge corridor connecting Ningbo and Zhoushan archipelagos. Upon full commissioning, the crossing will deliver expressway access to Meishan, Liuheng and Fodu islands for the first time. The upgraded transport network strengthens the comprehensive collection and distribution logistics system supporting Ningbo Zhoushan Port. Improved inter-island connectivity reshapes the spatial development framework of the Zhoushan Archipelago New Area and unlocks coordinated growth for port facilities and industrial clusters spread across the three linked islands.
National transport infrastructure research bodies record that prefabricated composite pylon and permanent-temporary cofferdam technologies trialled on this crossing have formed replicable technical standards for large-span multi-tower cross-sea bridges along China’s eastern coastal waters. Additional auxiliary works including deck surfacing, safety barrier installation and navigational marking systems will progress sequentially across the coming months to meet the full opening timetable for the second phase of the Liuheng cross-sea highway scheme.
