中文摘要：

考虑接拼梁段相位的变化（包括其轴线水平倾角相对于基准相位时的改变量）、顶推平台上梁段绀拼的线形误差，财顶推施工桥梁梁体无应力线形的高精度实现问题开展研究。提出梁体无应力线形的相位、基准相位、即时相位和定位基准线等概念，通过刚体平移和转动，实现基准相位与即时相位下坐标换算，建立了实测高程基准相位下的换算公式，以及待拼（浇）梁段定位高程即时相位下的换算公式，明确了节段无应力线形偏差逐步调整的数学表示法，解决了顶推施工桥梁已拼（浇）梁体无应力线形的评价与待拼梁段定位高程确定的关键问题。福元路湘江大桥河西引桥钢槽梁顶推施工的工程实例表明：按上述方法适时评价已拼梁体无应力线形，确定待拼梁段定位高程，并据此进行施工，桥梁顶推过程顺利，梁体全长的无应力制作线形与无应力目标线形吻合良好。

英文摘要：

Considering the phase shift of jointing segment （ including the variation of axial horizontal angle in its reference phase） and the geometry deviations of segment assembly in launching platform, the realization of geometry with high precision for incrementally launched girder is achieved in this study. Firstly, some relation to unstressed concepts including phase, reference phase, instant phase and positioning datum line, are proposed for unstressed girder geometry. Furthermore, coordinate transformation between reference phase and instant phase is performed through translation and rotation of rigid body; transformation formulas under positioning elevations and instant phase for preassembled （ or precast） segments of girder are established; the mathematical expressions of gradually adjusting the unstressed geometry error in the assembly process are determined. These achievements lead to the final settlements of the key problems in the evaluation of the unstressed geometry of assembled （or casted） segments as well as the determination of the positioning elevation of preassembled segments for incrementally launched bridges. The incremental launching process of the steel channel girder for the west approach of Fuyuan Bridge over Xiangjiang River is studied and it is shown that if the unstressed geometry of assembled segments is evaluated appropriately based on the proposed procedure and the positioning elevation of preassembled segments is determined, the unstressed girder geometry of the entire girder may perfectly match the aiming geometry considering that the above procedure is strictly followed and the launching process of girder is successful.