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　　On December 30, 2021, the Oujiang North Estuary Bridge in Wenzhou, Zhejiang Province, the world’s first steel truss double-deck suspension bridge with three towers and four spans, completed closure. With the design supervised by the China Railway Major Bridge Reconnaissance & Design Institute and construction participated by the China Railway Major Bridge Engineering Group and China Railway Hi-Tech Industry Corporation Limited, the bridge set three world records: the world’s first steel truss double-deck suspension bridge with three towers and four spans, the world’s first multi-tower bridge using concrete to build the central tower, and the world’s first bridge with super-large open caisson in deep soft soil of a strong-tide estuary.  

　　The construction of the bridge faced daunting technical difficulties and complicated technical procedures. Many innovations were made in the design and construction. By building three towers and four spans for the main cross-river part, it solved the height limit in sea and air transportation. For the first time, super-large open caisson was built in deep sludge of typical marine environment. The main beam features a continuous double-deck steel truss structure, which significantly improves the bridge’s wind resistance, ensures smooth pass of vehicles, saves transportation lane resources and complies with eco-friendly engineering standards. The new lengthwise A-shape concrete structure for the central tower with tower saddles made from comb plates ensures skid resistance, saves construction and maintenance costs, and improves the overall stiffness of the structure. The procedure for placing the suspension girders was complicated and both split-type and regular gantries were used. The girders for the two main spans were placed simultaneously, requiring high accuracy in gantry control. Given six joints in closing the bridge, the construction needed to be very accurate in calculation, rational in placement order, and efficient in procedure implementation. 

　　With the construction stretching in a course of three years, the bridge is the first in China applying BIM technology in the whole life cycle of construction. China Railway Shanhaiguan Bridge Group successfully cracked a world-level problem of manufacturing 20-meter-long bridge deck slabs, enabling one take in welding the bridge deck. In closing the bridge, the modular-based assembly technology developed during the building of the Shanghai-Suzhou-Nantong Yangtze River Bridge was applied, which made it possible to finish the closure with zero error.