既有简支梁桥整体同步顶升施工技术

Construction Techniques of Global Synchronized Jacking for Existing Simply-Supported Beam Bridge

某下行匝道桥为4×25m简支梁桥,单跨空心板梁重约500t。为了与新建城市快速干道高架桥连接成网,采用断柱顶升接高方法,对该桥进行整体反坡顶升改造,最大顶升高度2.5m。顶升控制系统为同步顶升不平衡高差控制系统,顶升导向装置为自行研制的缓冲导向装置。采用锚固于承台基础上的钢管与型钢组成顶升托架体系,单墩处布置4台200t千斤顶,每台千斤顶配置1台随动保护装置;安装调试好顶升系统后,对千斤顶施加梁体重量85%的预顶力,采用新型绳锯无震动直线切割立柱;顶升前,称重梁体,试顶后正式顶升,每个循环逐跨依次顶升10cm;对断柱续接断面进行特殊处理,续接断面植筋、安装模板后,浇筑续接段混凝土。实践表明,该桥断柱顶升接高施工技术安全高效、便于操作。

A descending ramp bridge is a 4×25m simply-supported beam bridge and the void plate beam in a single span weighs about 500 t.To become part of a transportation network after being connected to the newly-built city corridor viaduct,the technique of damaged column jacking and elongation was used to do integral reverse slope jacking rehabilitation,with a maximum jacking height of 2.5m.The jacking control system is the parallel jacking system that can control unbalanced height difference,and the jacking guiding device is the buffering guiding device developed by China Railway First Group.The jacking supporting system is formed of the steel tubes anchored to the pile cap foundation and the section steels.Four jacks,with capacity of 200 teach,were placed at each single pier,and every jack is equipped with a synchronized protection device.After the adjustment of the jacking system,apre-jacking force of 85% of the weight of the beam should be applied to the jacks and a new type of no-vibration straight line cutting machine was used to cut the vertical columns.Before jacking,the beam should be weighted,and after the trial jacking,the formal jacking began,jacking up 10 mspan by span in each cycle.The cross section from which the damaged columns should be expanded needs special treatment,after the reinforcing bars were planted and formwork was installed,the concrete in the added section was cast.The engineering practice proves that the jacking and elongation construction technique used to the damaged columns is safe,efficient and convenient for operation.