大吨位曲线斜拉桥大偏心转体结构优化技术

Optimization Techniques for Large-Eccentric and Large-Tonnage Structure Rotated During Construction of Curved Cable-Stayed Bridge

信阳新十八大街跨编组场大桥采用(150+150) m曲线宽幅钢箱梁独塔斜拉桥跨越既有铁路,采用平面转体法施工,转体最大双悬臂长(144.5+144.5) m,顺时针转体73.5°,转体重量约1.8万吨、主梁横向偏心达3.228 m。为减小结构的不平衡弯矩,实现转体平衡,采取了桥塔横梁以上塔柱倾斜3°、桥塔及转体系统设置横向偏心等转体结构预偏心优化技术,使转体结构重心与转体球铰中心重合,从理论上消除转体结构的横向偏心。经过转体预偏心优化,最大双悬臂状态下转体结构平衡性和转体支撑系统安全性明显改善,但裸塔状态下结构的横向偏心较大、转体支撑系统承载力不足。经分析进一步采取主梁临时配重技术,解决裸塔状态下结构的横向不平衡问题,完成了大桥平衡转体施工。

The 18 th Street Bridge that crosses a marshaling yard in Xinyang City is a curved,wide steel box girder cable-stayed bridge.The bridge has a monopole pylon that creates two equal spans of 150 m.Due to the limited construction space,a plane rotation method was selected.During construction,the superstructure at the longest cantilever state,with two cantilevers stretching 144.5 m each,was rotated 73.5° in a clockwise manner into position.The rotated structure weighed about 18 000 t and the lateral eccentricity of the superstructure reached up to 3.228 m.To mitigate the unbalanced bending moment of the superstructure and achieve rotation balance,the pylon pole above the cross beam was set to incline 3°,and the pylon and the rotation system were set with lateral eccentricity,to enable the center of the gravity of the rotated superstructure to overlap the center of the spherical hinge,aiming to theoretically eliminate the lateral eccentricity of the superstructure.After the optimization of the pre-eccentricity of the superstructure,the superstructure was better balanced at the maximum two-cantilever state,and the security of the rotation supporting system was remarkably improved.However,at the freestanding state of the pylon,the lateral eccentricity of the superstructure was greater and the load bearing capacity of the rotation supporting system was insufficient.By further analysis,temporary counterweights were added to the superstructure to resist the lateral eccentricity of the superstructure at the freestanding state of the pylon,to ensure the completion of the balanced rotation construction of the bridge.