Research on Fitting Technique of Incremental Launching Trajectory of Complex Composite Linear Steel Truss Girder
The construction of incremental launching method belongs to the ectopic installation,that is,the installation position of the steel truss girder is different from that of the finished bridge.During the incremental launching construction,the steel truss girder should be raised as a whole and pushed along the suitable incremental launching trajectory.Finally,the whole girder falls to the alignment of the finished bridge.The proper incremental launching trajectory is very important to the incremental launching construction.Based on the background of the Yongning Bridge Project in Zhejiang Province,aiming at the composite alignment of large longitudinal slope+complex vertical curve of the project,three forms of parabola,elliptic curve and circular curve are used to fit the incremental launching trajectory.Finally,the incremental launching trajectory is determined as the single circle curve with a radius of 15 670 m.The incremental launching construction is changed from the rigid rotation+translation to rotation around the fixed center of the circle,which effectively reduces the construction difficulty and risk,and provides the relevant experience for the incremental launching construction of subsequent complex composite curves.
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