Key Construction Techniques for Steel Box Girders of Gaolan Port Bridge of Huangmaohai Link
The Gaolan Port Bridge of Huangmaohai Link is a cable-stayed bridge of a full floating system.The bridge has two pylons that create a main span of 700 m,two side spans of 248 m and two end spans of 110 m.The stay cables are fanned out in double cable planes.The superstructure consists of split steel box girders that were cantilever-assembled by deck cranes,where the typical girder segments weighed 370 t and maximum girder segments weighed 468 t.To ensure the wind-resistant safety of the bridge during construction,the pylons and the superstructure were temporarily anchored in three directions to accommodate the unbalanced forces and moments,and the mechanical property of the three-way temporary connection was numerically simulated for verification.Temporary wind-resistant piers were added in side spans,based on the analysis of the load bearing behaviors of which,it was determined to use the steel pipe piles of φ1 200 mm×12 mm for the foundations of temporary piers,as well as steel tubes ofφ426 mm×6 mm for lateral bracings and diagonals,to ensure the safety of the under-construction main bridge during typhoons.The steel box girders were precambered to ensure the transverse slopes of the deck after completion of bridge.When the under-hoisting segment and the already-installed segment were matched,the brackets were applied with paired reaction forces to effectively reduce the matching elevation differences.After the second-phase tensioning of segments adjacent to the pier-top segments in the side and auxiliary spans,the side and auxiliary spans were closed,to avoid the occurrence of negative reaction forces at the bearings on top of the side and auxiliary piers.The main span was closed after a series of operations,including single-sided hoisting,arranging counterweights,as well as matching and cutting under natural temperature difference.