Control of Self-Adaptive Unstressed Configuration for Incrementally Launched Girder Bridges: Fid-Bau Portal

Control of Self-Adaptive Unstressed Configuration for Incrementally Launched Girder Bridges

Li, Hongli

Abstract The configuration of the main girder not only affects the appearance of the bridge, but also directly relates to the mechanical performance of the bridge, which is one of the key objectives for construction control. This paper presents a new geometric-control method (the phase-transformation method) of the self-adaptive unstressed configuration for incrementally launched girder bridges. The phase change of the prefabricated girder (i.e., the relative change of the in-plane horizontal angle and displacement) and the geometric deviation of the assembled segment in the assembly platform are considered in the procedure. First, some basic concepts of the key control parameters are introduced, such as the theoretically unstressed configuration, the reference phase, and the current phase. Next, the coordinate transformations under both the reference and instantaneous phase are derived based on the translation and rotation of the girder's rigid motions. In order to gradually adjust the errors of the unstressed configuration in the assembly process, the unstressed configuration for the already-assembled segments at the reference phase is evaluated, and the unstressed configuration for the ongoing-assembly segments at the instantaneous phase is predicted. Finally, the proposed method is applied and validated in an incremental-launching process of a steel box girder for the Fuyuan Bridge over the Xiangjiang River in China. The predicted configuration of the steel box girder agrees well with the measured configurations; this indicates that the proposed method can effectively evaluate the unstressed configuration for already-assembled segments and can accurately predict the unstressed configuration for the ongoing-assembly segment during the entire incremental-launching process.