500m级上承式CFST拱桥施工挑战及创新

Construction Challenges and Innovations of 500-meter Level CFST Deck Arch Bridge

贵州德江(合兴)~余庆高速公路乌江特大桥主跨504 m,是目前世界上在建的最大跨径上承式钢管混凝土拱桥。该桥采用了全新拱—柱—梁全刚接协同受力体系,拱肋及肋间横撑、立柱及桥面系钢梁节段在现场全部采用高强螺栓连接,钢结构经乌江航道水运至现场经复拼后采用缆索吊装斜拉扣挂架设,桥位处于山区深“U”形峡谷,微气象效应明显。基于上述结构特点及建设条件,乌江特大桥在施工过程中面临的挑战包括:(1)构件现场全栓接要求安装精度控制在3 mm以内,需要进一步突破施工控制理论及技术;(2)拱肋管管径为1.4 m,顶升高度为90 m,内填机制砂C70混凝土,拱肋管内混凝土的密实度和脱空率难以保证;(3)拱上立柱预偏、主梁加工架设线形难确定。面对上述挑战,对主拱施工控制理论、扣挂系统设计及架设工艺工装、石灰岩机制砂C70自密实补偿收缩混凝土配合比设计、拱上结构施工控制理论等关键技术进行了创新研究,进一步丰富和发展了超大跨CFST拱桥施工技术。

The main span of the Wujiang Major Bridge on the Dejiang(Hexing)to Yuqing Expressway in Guizhou is 504 m,which is the largest span steel-tube concrete arch bridge under construction in the world.The bridge adopts a new full rigid joint synergistic force system for the arch-column-beam,the arch ribs,inter-rib cross braces,columns and steel girder sections of deck system are all connected by high-strength bolts at site,the steel structure is transported to the site by water through the Wujiang waterway,and after assembly in-situ,the steel structures are erected and installed by cable crane and buckling.The bridge site is located in the deep U-shaped canyon with obvious micro-meteorological effect.Based on the above structural characteristics and construction background,the challenges faced by the Wujiang Major Bridge in the construction process include:(1)the installation accuracy of the full bolting of the components needs to be controlled within 3 mm,and further breakthroughs in construction control theory and technology are required;(2)It is difficult to guarantee the compactness and voiding rate of concrete in the C70 arch rib pipe with a tabular diameter of 1.4 m and a lifting height of 90m;(3)It is difficult to determine the pre-deviation of the arch column and the alignment type of the main beam processing erection.In view of the above challenges,innovative research is carried out on key technologies such as main arch construction control theory,buckle system design and erection process tooling,limestone mechanism sand C70 self-compacting compensation shrinkage concrete mix ratio design,and arch structure construction control theory,etc.,which has further enriched and developed the construction technology of super-large span CFST arch bridge.