长阳天池口清江特大桥主拱圈悬臂浇筑斜拉扣挂系统设计

Design of Cable-Stayed Cantilever Casting System for Arch of Tianchikou Qingjiang River Bridge in Changyang County

长阳天池口清江特大桥主桥为净跨径242 m的非对称上承式钢筋混凝土拱桥,主拱圈采用单箱单室截面,宽9.5 m、高4.0 m。资丘岸和五峰岸半跨主拱圈各分为24个和21个节段,第1个节段采用支架现浇,其余节段采用斜拉扣挂悬臂浇筑法施工。扣索采用星式和扇形组合方式布置,位于墩顶和扣塔的扣索为星式布置,位于交界墩墩身的扣索为扇形布置,并将墩身上的扣锚索设计成连续索以避免在墩身上搭设张拉平台;扣塔由8根∅800 mm×16 mm钢管组成,两岸扣塔分别高52.68 m和60.12 m;根据锚索最大索力,设计了能承受800 kN张拉力的岩锚索。建立主拱圈悬臂浇筑施工阶段MIDAS Civil有限元模型,对斜拉扣挂系统扣锚索索力进行计算,通过拆除部分扣索和调整扣锚索索力,施工期间主拱圈截面最大拉应力、扣塔最大偏位、主拱圈成拱后线形均满足要求。

The main bridge of Tianchikou Qingjiang River Bridge in Changyang County is an asymmetric deck-type reinforced concrete arch bridge.The arch,spanning 242 m,is of single-cell box cross-section,measuring 9.5 m wide and 4.0 m deep.The two halves of the arch on Ziqiu side and Wufeng side were composed of 24 and 21 segments,respectively.Except the segment No.1 that was cast on scaffolds,the remaining arch segments were all cast using a cable-stayed cantilever casting system.The forestays and backstays were radiated out from the temporary towers,while the forestays and backstays connecting the transition piers and arch were in fan arrangement,and these stays were designed as continuous stays,to save the installation of traditional stay tensioning platform.The two temporary towers rose 52.68 m and 60.12 m,respectively,each consisting of 8,∅800 mm×16 mm steel pipes.The rock-anchored stays with 800 kN capacity each for the cable-stayed cantilever casting system were designed considering the maximum tensions of the stays.The cable-stayed cantilever casting system was simulated in MIDAS Civil to determine the stays that would be demolished and adjust tensions of stays.During construction,the maximum cross-sectional tensile stresses in the arch,the maximum displacements of the temporary towers,and the geometry of the completed arch met the requirements.