商合杭铁路芜湖长江公铁大桥桥塔上横梁施工关键技术

Key Construction Techniques for Upper Pylon Cross Beams of Wuhu Changjiang River Rail-cum-Road Bridge on Shangqiu-Hefei-Hangzhou Railway

商合杭铁路芜湖长江公铁大桥主桥为主跨588 m的双塔双索面矮塔箱桁组合梁斜拉桥,采用门形钢筋混凝土桥塔,桥塔设上、下2道横梁。上横梁采用预应力混凝土结构,净跨度30 m,高7~15 m,采用“牛腿+支架”法分层浇筑的总体方案施工。支架采用跨度29.6 m的桁架结构,顺桥向布置10片,通过钢牛腿支撑在塔柱侧壁;支架利用2台800 t塔吊,采用分组抬吊的方式安装。施工时,预埋件由锚筋及锚板穿孔塞焊而成,从塔柱水平预应力管道之间交错穿过;上横梁钢筋按施工接缝分次绑扎,采用液压爬模和翻模组合模板;上横梁混凝土分3层与两侧塔柱同步浇筑,并采用增设抗拉钢筋和提前张拉部分预应力束的方法预防先浇混凝土受力开裂;上横梁施工后,支架采用整体下放法拆除。

The main bridge of Wuhu Changjiang River Rail-cum-Road Bridge on the Shangqiu-Hefei-Hangzhou Railway is a two-pylon extradosed bridge with a main span of 588 m.The main girder is a box-truss composite structure,and the stay cables are fanned out in double cable planes.The pylons are reinforced concrete portal pylons,each with an upper cross beam and a lower cross beam.The upper cross beam is a prestressed concrete structure with a net length of 30 m,7-15 m in depth,and cast in layers with brackets and scaffolds.The scaffolds consisted of trusses,spanning 29.6 m,along the bridge length,10 trusses were arranged,which were attached to the pylon walls via the steel brackets.The scaffolds were lifted and installed in groups using two lifting towers of 800 t capacity each.During the construction process,the embedded connectors were welded from anchor reinforcement and anchor plates,with the anchor reinforcement going through the holes in the anchor plates,and the anchor reinforcement alternately threaded through the horizontal prestressed conduits in the pylon columns.The reinforcement in the upper cross beam was bundled by several times in accordance with the construction joints.The hydraulic climbing formwork and rollover formwork were used.The concrete in upper cross beam was cast in three layers,synchronized with the casting of the two pylon legs.Tensile reinforcement was added and a portion of the prestressing tendons were tensioned in advance to prevent the cracking of the already-cast concrete.After the construction of the upper cross beam,the scaffolds were monolithically lowered and dismantled.