连续钢箱梁桥顶推施工主梁线形修正方法研究

Updating method on geometric shape control of continuous steel box girder bridges by incremental launching construction

为提高顶推施工钢箱梁桥主梁线形控制精度,提出一种线形偏位向量转换方法,该方法对理想状态下的传递矩阵法进行了修正,可实现对顶推施工钢箱梁纵轴线水平向偏位与竖向偏位的阶段性矫正。建立用以识别钢箱梁线形状态的空间坐标系统,以钢箱梁节段两端控制点水平坐标与高程为基本变量,基于已拼装梁段上各控制点实际坐标与设计坐标差,构造梁段线形偏位向量与偏位平方和表达式;通过求解偏微分方程极值,对已拼装梁段线形进行计算转化,得到整体线形偏位离散度最低时的“转换线形”;比较“转换线形”与“理论线形”,对待拼装梁段拼装线形进行修正。实际工程应用表明,采用该方法控制顶推施工钢箱梁拼装线形,成桥阶段全桥顶推段主梁线形轴线水平向偏位值低于5 mm,竖向偏位值低于15 mm,永久墩处梁段轴线水平向偏位与竖向偏位分别低于4和10 mm,线形控制精度满足规范要求。

A new method of deviation vector transformation of geometric shape was proposed to improve the accuracy on geometric shape control of continuous steel box girder bridges by incremental launching construction.The method correct the transfer matrix method in the ideal state where the lateral and vertical deviations of longitudinal axis at the segments can be adjusted periodically.By firstly constructing a spatial coordinate system for identifying the geometric shape of the box bridge and taking the elevation and horizontal coordinates of the control points at both ends of the installed bridge segment as the basic variables,the actual and design coordinates of the control points will be obtained in the constructed coordinate system,constructing the vector of deviation system on geometric shape and the sum of vector squares,and then the extremum problem of the partial differential equation is solved to obtain the"transformed shape"with the lowest dispersion of overall deviation.The modified term appended to transfer matrix method aforementioned for bridge segment to be installed can be obtained ultimately by deriving from the"transformed shape"and"designed shape".Engineering practice shows that the horizontal and vertical maximal deflections on the axis of the whole bridge at post construction are less than 5 and 15 mm,respectively,by using the proposed method to control the geometric shape of a continuous steel box girder bridge by incremental launching construction method,meanwhile,the horizontal and vertical deflections on the axis of the segments above the permanent piers are less than 4 and 10 mm,respectively.The theoretical method has been verified with good effect in requirement of the code.