某城际铁路车站天桥主动托换施工方案

为解决城际铁路钢箱梁天桥桩位跨径变化后托换施工的若干关键技术问题，采用主动托换支架结构、PLC同步顶升主动托换、钢箱梁横隔板底部局部加固等关键技术，提出一种可靠的主动托换施工方案，并采用有限元软件分析PLC顶升时结构的力学行为。研究表明，实施主动托换后，桥梁上部结构的传导路径变为上部结构→桥墩→托换支架→地面，原有桥墩在人为截断后不再承受来自桥梁上部结构的荷载，可有效解决上部结构的受力托换问题；相比于被动托换中原桥墩截断瞬时转换荷载传递路径，主动托换通过可控制千斤顶分级加载、顶升过程和可补偿被动托换时托换柱受荷载作用之后的弹性压缩，使荷载传递路径转换更为平稳，从而有效保护桥梁结构。

Construction Scheme of Active Underpinning foran Intercity Railway Station Overpass

In order to solve some key technical problems in underpinning steel box girder overpass for intercity railway after pile position and span change,a reliable construction scheme of active underpinning is proposed which combines the key technical points of active underpinning support structure,PLC synchronous lifting active underpinning process and local reinforcement at the bottom of steel box girder diaphragm,and a finite element analysis made of the mechanical behavior of structure during PLC lifting.The research shows that after the implementation of active underpinning,the transmission path of the bridge superstructure changes to be superstructure→pier→underpinning bracket→ground,and the original pier no longer bears the load from the bridge superstructure,which resultantly solves the problem of stress underpinning of the superstructure.The active underpinning can control the jack step loading and jacking process and compensate the elastic compression of the underpinning column after the load,which produces a more stable load transfer path transition than the passive underpinning mode,thus helping protect the bridge structure effectively.