五峰山长江特大桥铁路二期恒载加载时机方案比选

Comparison and Selection of Time Schemes for Applying Second Phase Railway Dead Load to Wufengshan Changjiang River Bridge

五峰山长江特大桥主桥为主跨1 092m的钢桁梁公铁两用悬索桥,该桥加劲梁恒载集度大、铁路二期恒载占比高,加劲梁采用整节段吊装施工。针对该桥特点,提出了铁路二期恒载在加劲梁合龙后加载(吊重约1 450t,采用2台900t缆载吊机,方案1)和铁路二期恒载与加劲梁整节段同步架设(吊重约2 100t,采用2台1 300t缆载吊机,方案2)2种方案,并采用MIDAS Civil软件建立全桥有限元模型,从加劲梁线形及节段下弦间开口的闭合时机、边跨钢梁合龙位移调整量和节段间上弦临时铰受力等方面进行综合比选,选择方案1。方案1满足加劲梁整节段架设要求,同时显著降低了缆载吊机的起吊能力,在经济性上有较大的优势。

The main bridge of the Wufengshan Changjiang River Bridge is a rail-cum-road steel truss girder suspension bridge with the main span of 1 092 m.The dead load intensity of the stiffening girder of the bridge is great,the proportion of the second phase railway dead load is high and the stiffening girder is to be constructed,using the integral segment hoisting and erection method.In the light of the characteristics of the bridge,2 schemes of applying the second phase railway dead load to the bridge after the stiffening girder is closed(scheme 1,the hoisting weight is about 1 450 t and 2 sets of 900 t capacity cable-supported cranes are to be used)and of applying the railway dead load and erecting the integral segments of the stiffening girder in the same step(scheme 2,the hoisting weight is about 2 100 t and 2 sets of 1 300 t capacity cable-supported cranes are to be used)are put forward.The software MIDAS Civil is used to create the finite element model for the whole bridge of the bridge,the alignments of the stiffening girder,the closure time of the gaps between the lower chords of the segments,the adjusting amounts of the displacement of the side span steel truss girder and the force conditions of the temporary hinges between the upper chords of the segments are comprehensively compared and the scheme 1 is eventually selected.The scheme 1 can accommodate to the requirements for the erection of the segments of the stiffening girder and moreover,can obviously decrease the hoisting capacity of the cable-supported cranes and economically,also has rather great advantage.