五峰山长江大桥铁路二期恒载铺设技术

Techniques to Apply Secondary Dead Loads on Railway Deck of Wufengshan Changjiang River Bridge

连镇铁路五峰山长江大桥为主跨1092 m的公铁两用悬索桥,该桥加劲梁一期恒载为501 kN/m,二期恒载为318.1 kN/m,其中二期恒载中的铁路道砟为189.4 kN/m。加劲梁采用不携带二期恒载整节段架设、合龙后铺设二期恒载的方法施工。由于二期恒载达到加劲梁恒载的38.8%,加劲梁合龙后,加劲梁线形未达到成桥线形,在铁路道砟集中摊铺过程中,面临着加劲梁桥面系局部应力分布不均的难题。针对该桥特点,通过分析,该桥有砟轨道采用分阶段对称隔断与连续摊铺相结合的方案施工,将4线铁路分4个阶段进行铺设,阶段1和阶段2采用对称隔断的方式进行底砟及预留线道砟摊铺,阶段3和阶段4采用单向连续的方式进行连镇线轨枕及面砟摊铺。该摊铺方案引起的主缆线形变化较为平缓,避免了施工过程中加劲梁桥面系局部应力集中的问题,采用所提出的方案施工后该桥线形及加劲梁内力控制均较好。

The Wufengshan Changjiang River Bridge of Lianyungang-Zhenjiang High-speed Railway is a rail-cum-road suspension bridge with a main span of 1092 m.The dead loads imposed by the pure stiffening girder were 501 kN/m,and the secondary dead loads were predicted to be 318.1 kN/m,in which the railway ballast contributed 189.4 kN/m.The secondary dead loads were applied after the closure of the stiffening girder.Due to that the secondary dead loads reached about 38.8%of the dead loads of stiffening girder,after closure,the geometry of the stiffening girder would not achieve the design objective,during the placement of the railway ballast,there would be uneven stress distribution in the deck system of the stiffening girder.The ballast tracks of the bridge were placed by the combined utilization of staged symmetrical partition and continuous placement.The four-track railway was placed in four stages,in stages 1 and 2,the bottom ballast and the ballast underlying the reserved track were placed by symmetrical partition method,while in stages 3 and 4,the sleepers and surface ballast were paved continuously towards one direction.By using the proposed methods,the geometrical variation of the main cables was smooth,avoiding the local stress concentration in the deck system of the stiffening girder,the alignment of the bridge was under control and the internal forces of the stiffening girder achieved the required levels.