The construction method for temporary cable towers of the large-span steel box girder swivel bridge was awarded the Shandong Provincial Excellent Construction Method and the First Prize of China Railway Construction Corporation Excellent Construction Method; the comprehensive construction technology for the high-position, wide-width, large-span steel box girder double-T-frame swivel bridge crossing multiple operating railway lines was awarded the Second Prize for Scientific and Technological Progress by the China Association of Construction Enterprise Management... Recently, the First Company of China Railway 14th Bureau Group has achieved multiple scientific and technological accomplishments. This is strong evidence of the company's active implementation of the value creation initiative and enhancement of independent innovation capability.

　　The swivel bridge on the Qingdao New Airport Expressway Connection Line, constructed by China Railway 14th Bureau Group, is a controlling project of the entire line. It is currently the world's largest-span steel box girder swivel bridge and China's first municipal swivel bridge in which the entire girder adopts an all-welded, coating-free weathering steel structure. The swivel bridge is designed as a 240-meter T-frame steel box girder, arranged in two parallel decks, with a single deck width of 24.58 meters and a total width of 49.53 meters; the total swivel weight reaches 19,000 tons. On November 4, 2020, the bridge successfully completed its rotation in 90 minutes.

The swivel bridge after completion of the main structure (Photo by Fang Zian)

　　It is understood that the swivel bridge crosses six existing railways, including the Jiaozhou-Jinan Railway and the Qingdao-Rongcheng Intercity Railway, as well as one urban arterial road. It is adjacent to a river channel and constrained by airport aviation height restrictions, making the construction environment exceptionally complex and rare. Due to the narrow site, the builders divided the required steel box girders into 85 segments and used BIM technology for modeling. The modules were constructed using the method of "first entering the site, then welding, and then assembling," which solved the transportation problem of the box girders and also addressed the dilemma of the construction site "waiting for materials to start work."

　　Compared with ordinary girder hoisting, the steel box girder hoisting of this project was extremely difficult. The 85 steel box girder segments had to be lifted to a 20-meter-high support for large-block assembly, with a maximum hoisting weight of 80 tons and a minimum weight of 13 tons. There was no domestic precedent for lifting and hoisting in such a complex environment. In response, the builders repeatedly demonstrated and optimized the hoisting plan, installed four large gantry cranes 33 meters high and 120 tons in weight, and integrated a streamlined operation mode of "transport, hoist, and erect," effectively shortening the detention period. Among these, the gantry crane installation innovatively adopted the "horizontal assembly and integral lifting installation" scheme, greatly ensuring the operational safety of the railways along the line.

　　After the steel box girder hoisting was completed, in order to reduce the girder height and the deflection at the girder ends during the swivel stage, lower the difficulty of alignment control and the risk of swiveling, make the girder evenly stressed during rotation, and ensure a smooth swivel, the builders installed a temporary cable tower at the center of each of the two swivel bridge decks. The center height of each cable tower is 19.87 meters above the bridge deck, and 20 cable stays on each side of the tower tighten the bridge deck. To further improve the safety of the swivel bridge rotation, the builders optimized the temporary cable tower process. The optimized temporary cable tower increased the inclination angle of some temporary stay cables, which can reduce the cable force and horizontal component force of the temporary stay cables while ensuring that the vertical component force remains unchanged, making the stress on the temporary tower columns more balanced.

　　It is reported that the project team actively carried out "invite in and go out" activities and conducted scientific and technological innovation activities through measures such as establishing a technical research team for "construction of a double-deck (120+120) meter steel box girder swivel bridge in a complex environment" and a BIM innovation studio. Up to now, the project has been awarded the 2023 Shandong Provincial Construction Project Taishan Cup, the Shandong Provincial Construction Safety and Civilized Standardization Site, and the 2020 Shandong Provincial Construction Project Quality Structure Project. It passed the green construction evaluation of the Shandong Civil Engineering and Architecture Association with an "Excellent" rating. It has obtained 3 utility model patents, 2 invention patents, 4 provincial and ministerial-level construction methods, 3 QC achievements, and 1 BIM excellence award, and has published 8 journal papers, achieving good scientific and technological benefits and social benefits.