大跨度连续钢箱梁悬索桥无索区钢梁施工控制技术

Construction Control of Steel Box Girders in Zones Without Hanger Cables in Long-Span Suspension Bridge

秀山大桥为主跨926 m的三跨连续弹性支承体系钢箱梁悬索桥,无索区梁段采用临时高支架+永久吊索法拼装,支架采用“钢管支架+纵移轨道”形式。采用MIDAS Civil软件建立主桥有限元模型,基于无应力曲率的全过程迭代法进行施工控制计算,确定无索区梁段支架预抬量和无索区梁段拼装线形,以及支架反力和索梁内力。通过计算,官山侧桥塔无索区梁段支架预抬量最大值0.625 m、最小值0.600 m,无索区梁段理论线形与设计值最大偏差-4 mm,支架各支点反力均匀,钢箱梁合龙后第1对吊索索力仅增大4.5%,无索区梁段内力变化较小。钢箱梁施工时,利用缆载吊机荡移法起吊无索区梁段至预定位置,采用液压千斤顶和移位器调整无索区梁段支架预抬量和梁段间拼装线形;利用缆载吊机起吊无索区相邻的第1对吊索梁段并与之精调连接,整体环焊结束后拆除支架。无索区梁段支架拆除后实测高程最大偏差-7 mm,桥面纵坡最大偏差-0.0373%,满足设计要求;成桥后钢箱梁纵坡最大偏差0.264%,成桥线形平顺光滑。

The Xiushan Bridge is a suspension bridge featuring the stiffening girder composed of steel boxes.The bridge is of a three-span continuous elastic supporting system,with the main span length reaching 926 m.The steel box girders in the zones without hanger cables were erected on high scaffolds,assisted by permanent hanger cables.The high scaffolds were composed of steel tubes,on the top of which tracks were laid for the longitudinal moving of the girders.The main bridge was numerically simulated in MIDAS Civil software to carry out construction control calculation,and a full-process iteration method based on stress-free curvature was used,to determine the precamber of the scaffolds as well as the assembly alignment of the girders in the zones without hanger cables.As per the calculations,the maximum and minimum precambers of scaffolds in the vicinity of Guanshan-side tower without hanger cables were 0.625 m and 0.600 m,respectively.The maximum bias of the theoretical and design alignments of the girders in the zones without hanger cables was-4 mm.Reaction forces at supports of the scaffolds were even.After closure of the stiffening girder,the tensions of the first pair of hanger cables were only increased by 4.5%,and the internal forces of the steel box girders in the zones without hanger cables showed minimal change.During construction,the steel box girders in the zones without hanger cables were first swung to the stipulated locations by the main-cable-supported cranes,and then precamber of scaffolds as well as the assembly alignment of the steel box girders were adjusted by the hydraulic jacks and tuners.Afterwards,the steel box girders suspended by the first pair of hanger cables were tuned and connected with the neighboring steel box girders in the zones without hanger cables.The scaffolds were dismantled after the completion of the overall loop welding,and in this case,the maximum elevation bias of the girders in the zones without hanger cables was-7 mm,the maximum bias of deck longitudinal gradient was-0.0373%,meeting the design requirements.After the completion of the bridge,the maximum bias of the longitudinal gradient of steel box girders is 0.264%,indicating smooth alignment.