大跨度六线简支钢箱叠拱桥顶推施工关键技术

北京铁路枢纽丰台站改建工程丰台特大桥为1-112 m六线简支钢箱叠拱桥,拱肋采用上、下拱组成的双层拱形式,桥幅全宽38.6 m,总重达4795 t。根据该桥结构特点及施工条件,拱桥采用非桥位现场拼装,整体顶推至设计桥位的施工方案,即在桥位小里程侧顺桥向搭设临时墩、贝雷梁拼装平台,利用履带吊和汽车吊分段拼装拱桥,采用1000 t步履式顶推千斤顶多点、多次同步顶推到位,利用500 t千斤顶进行落梁施工。顶推过程中,纠偏油缸可以左、右边同步控制伸缩,通过对步履式千斤顶和临时支垫标高进行调节,在螺栓节点处设置盖板,采用导梁上墩措施,以及铁路营业线封锁要点施工技术,确保了顶推施工顺利完成。

Key Incremental Launching Techniques for Long-Span Simply-Supported Composite Arch Bridge Accommodating Six Rail Tracks

Fengtai Bridge is the part of the Fengtai Railway Station(a railway terminal)Upgrading Project in Beijing.The bridge,which is a combined simply-supported steel box and arch bridge with a single span of 112 m,accommodates 6 rail tracks,with a total deck width of 38.6 m and weighing up to 4795 t.The bridge features its vertically parallel two arches with different rises.Considering the structural characteristics of the bridge and the construction challenges at the bridge site,the off-site assembly and field incremental launching construction method was proposed.First,temporary piers and bailey truss platform were installed,relying on which,the arch and deck segments were assembled using crawler crane and mobile crane to be an integral structure.Then,the finished entire arch structure was launched into place by hydraulic-walking jacks with a capacity of 1000 t from multiple points and in stages.The 500 t-capacity jacks were employed to lower the deck.During the jacking and pushing process,the expansion and compaction of the oil cylinder could be controlled from both the left and right sides in a synchronized manner.Various techniques were used to ensure the success of the incremental launching construction,including adjusting the elevation of the hydraulic jacks and temporary pads,adding cover plates at the locations of bolts,lifting and mounting launching nose on pier tops and temporarily closing the operation of the railway.