Fabrication and Installation Technique for Arch Ribs of Main Bridge of Jiubao Bridge in Hangzhou

The main bridge of the Jiubao Bridge in Hangzhou is a(3×210) m arch bridge with steel-concrete composite girder.The arch rib system is composed of main arch ribs,subsidiary arch ribs,the cross ties between the main arch ribs and the subsidiary arch ribs and the lateral bracings on the top of the arch crown.The arch ribs were fabricated in segments in the shop,and the arch rib segments were assembled into an integrated whole on site and then incrementally launched.To ensure that the fabrication accuracy of the arch ribs could meet the related requirements,the main arch ribs and subsidiary arch ribs in each span were divided respectively into 14 and 13 lifting segments,the curvature of the arch ribs was approximately fit following the principle of straight line to replace curve line,and the specific moulding board was tailored for the fabrication.After the completion of fabrication,the arch rib segments were transported by the flat car to the main assembling yard and lifted to the assembling platform using the 120 t gantry crane.When the hanging hooks of the gantry crane were loosened,the three-directional leveling jack was applied to accurately adapt the elevation,longitudinal position and the transverse position,and then the welding of the arch ribs began.By using these methods,the construction of arch ribs of the Jiubao Bridge was carried through and the continuity of the geometrical shape of the arch ribs was ensured.Additionally,the accuracy and speed of the installation and positioning of the arch ribs were improved and the construction quality was also ensured.