南浦溪特大桥钢管拱肋悬拼阶段拱脚约束方式研究

南浦溪特大桥主桥为主跨258 m的钢管混凝土桁架上承式拱桥,拱肋为等截面钢管混凝土桁架结构,2道拱肋间距17.0 m,拱肋间布置13道横撑,单片拱肋由4根?1200 mm×22 mm主钢管、水平向缀板和竖向腹杆组成。拱肋在工厂分段、分部件加工预拼合格后,运至现场拼装成吊装节段,采用缆索吊装斜拉扣挂法进行悬臂拼装。拱肋吊装阶段拱脚的约束方式和约束时机选择直接影响拱肋的线形、受力状态和结构的安全稳定,采用MIDAS Civil软件对拱肋悬臂拼装过程中拱脚不同约束方式进行对比分析,最终确定“先临时铰接、后临时固结、最后永久固结”的拱脚约束方式,优化了钢管拱肋悬臂吊装施工工艺,保证了拱轴线线形,结构受力合理、安全稳定。

Study of Arch Spring Restraints During Cantilever Assembly of Steel Tubular Arch of Nanpuxi Bridge

The main bridge of Nanpuxi Bridge is a deck-type arch bridge with a main span of 258 m.The two arch ribs that are distanced 17.0 m are concrete-filled steel tubular truss structures with constant cross-section,and between which,13 lateral bracings are arranged.Each arch rib consists of 4 main steel tubes with dimensions of 1200 mm(diameter)×22 mm,horizontal batten plates and vertical web members.The arch ribs were divided into sections to facilitate the manufacturing.Checked qualified in pre-assembly,the individual components were transported to the bridge site to be assembled into segments for hoisting.A cable-stayed cantilever assembly system was established for the arch construction.How and when to restrict the arch springs during the hoisting of the arch ribs would directly influence the geometry and load bearing condition of the arch ribs as well as the safety and stability of the structure.Different restraint options for the arch springs in the cantilever assembly process of the arch ribs were analyzed by MIDAS Civil,and restricting pattern of transforming from temporary hinge connection through temporary fixed connection to permanent fixation was finally determined.The cantilever hoisting and installation technique for the steel tubular arches were optimized to ensure the geometry of the arch ribs,and the rational load bearing behavior,safety and stability of the structure as well.