大型城市环形立交大吨位同步顶升设计

Design of Great Tonnage and Synchronous Jacking-up for Large City Ring Overpasses

南昌市老福山-坛子口立交为多跨连续箱梁结构,经过多年运营桥梁支座功能失效,采用PLC多点同步液压顶升控制系统进行同步顶升更换支座。由于该桥顶升荷载达160 000kN、顶升长度达504m,采用钢管支撑和承台组合结构与预应力小盖梁作为顶升底盘结构体系;为控制梁体位移,采取匝道限位、辅助抗拔桩-钢丝绳限位体系与桥面牵拉限位装置的限位措施。利用有限元软件建立钢支撑和承台组合结构及预应力小盖梁结构模型,进行不同顶升工况的受力分析,结果表明:该结构体系在不同荷载工况下的承载能力均满足大吨位顶升的需求。工程实施结果表明:支撑体系具有足够的安全度,且各点同步位移误差控制在±2.0mm内。

The Laofushan-Tanzikou Overpass in Nanchang City is a multi-span continuous box girder structure.After years of operation,the bearings of the overpass can not effectively work and need to be replaced by synchronously jacking up the girder structure,using the PLC control system of multi-point and synchronous hydraulic jacking-up.In the replacement of the bearings,because the jacking-up load was to be 160 000 kN and the jacking-up length to be 504 m,the steel pipe support and pipe cap combined structure and the prestressed small capping beam were used as the jacking-up chassis structural system and to control the displacement of the girder structure,a series of the measures of the ramp limiting,auxiliary anti-pulling pile-steel rope limiting system and deck hauling limiting devices were taken.The finite element software was used to set up the models for the combined structure and the small capping beam and the structural force conditions under the different jacking-up load cases were analyzed.The results of the analysis show that the bearing capacity of the chassis structural system under the different load cases can meet the requirements for the great tonnage jacking up.The construction practice of the jacking up also proves that the support system of the jacking up has sufficient safety and the errors of synchronous displacement at the different points are controlled within ±2.0 mm.