钢管混凝土拱桥新增吊杆加固设计

Design of Retrofitting Concrete-Filled Steel Tubular Arch Bridge by Adding New Hangers

为改善吊杆承载能力及提升桥梁运营服务能力,以某跨径72m的下承式钢管混凝土系杆拱桥为背景,采用新增吊杆法对该系杆拱桥吊杆进行加固。按照新增吊杆总拉力为原桥恒载15%-20%的原则进行加固设计,经对比分析,各新增吊杆张拉控制值为160kN,总拉力约为该桥结构恒载的17.6%;在拱脚端间和各旧吊杆节间增设1根新吊杆,全桥共新增吊杆28根,新增吊杆采用JL32型精轧螺纹钢筋,其下端通过2个平行吊板与外径800mm的钢管系杆连接,上端穿越拱肋钻孔、锚固于拱肋上缘焊接的锚箱内;经仿真计算得到在结构恒载作用下新增吊杆可分担原吊杆12.5%的荷载,符合设计原则。采用新增吊杆加固法来维持或提高吊杆承载能力是可行的。

To improve the load bearing capacity of hangers and upgrade the bridge operation service,a bow-string concrete-filled steel tubular arch bridge with span length of 72 m was taken as the background.The hangers of the bow-string arch bridge were strengthened by the method of adding new hangers.The retrofitting scheme is designed on the basis that the overall tension force of the newly-added hangers should be 15%~20% of the dead load of the existing bridge.According to the comparison,the tensioning control value of each newly-added hanger is 160 kN and the overall tension force is about 17.6% of the dead loads of the existing bridge.A total of 28 hangers were added,among which one hanger was installed between the arch springs and one between each two hangers.The new hangers adopt the JL32screw-thread steel bars,the lower ends of which are connected to the steel tubular arch tie with an external diameter of 800 mm through 2parallel hanger plates,and the upper ends go through the holes in the arch ribs and are anchored to the anchoring boxes welded to the upper edges of the arch ribs.The simulation calculation indicates that the newly-added hangers can share 12.5% of the loads on the existing hangers under the action of the structural dead loads,conforming to the design principles.It is feasible to add new hangers to sustain or improve the load bearing capacity of the hangers.