芜湖长江三桥钢桁梁分层变幅法架设技术

芜湖长江三桥主桥为主跨588 m的双塔双索面斜拉桥,其钢主梁采用三角形桁式的双主桁布置,上层为板桁组合结构、下层为箱桁组合结构,采用分层变幅法进行钢主梁标准节段的悬臂架设。钢梁起吊设备选择整体底盘双臂杆结构,变幅范围为5~22 m的变幅式架梁吊机,站位于上弦杆节点处。钢梁采用“3+1”分层匹配法制造,运输船分层纵列运输至桥位。每个标准节段分2次吊装,先吊装下层节段(含腹杆),再吊装上层节段。节段对接时利用架梁吊机起落和变幅精确调整空间位置,打入一定数量的冲钉后即可松钩。2层吊装完成后进行节段间的高强度螺栓连接和焊接,然后架梁吊机向前走行,继续循环进行下一节段架设。分层变幅法架设技术利用变幅式架梁吊机将钢桁梁标准节段分下、上2层分别吊装,是继散拼法、桁片法、整节段法等之后钢桁梁架设方法的一个创新。

Layered Erection of Steel Truss Girders in Third Wuhu Changjiang River Bridge Using Derrick Crane

The main bridge of the Third Wuhu Changjiang River Bridge is a two-pylon cable-stayed bridge with a main span of 588 m.The stay cables are fanned out in double cable planes.The superstructure,which consists of two triangular main trusses,accommodates two levels of decks,the upper deck is a composite structure formed of orthotropic steel plates and trusses,and the lower deck is a box-truss composite structure.The standard steel main girder segments were erected in layers in the field using derrick crane.The derrick crane has an integral chassis and double masts,with working radius varying from 5 to 22 m.The crane can stand on the upper chords of the steel trusses at the nodes.The steel girders were prefabricated by the“3+1”layered match-cast method,and transported to the bridge site in layers and arranged in rows.Each standard segment was hoisted in two steps,first the hoisting of lower deck elements and then the upper deck elements.The segments were hoisted and lowered into position by the crane,and accurately adjusted for butt joint using the variable working radius of the crane.The hooks could be released after a number of impact pins were driven in.Once the hoisting and lowering of the two layers of elements in one segment was finished,the two adjacent segments were bolted and welded together,then the crane moved forward for the installation of the next segment,and the cycle was repeated till the completion of the superstructure.The standard steel truss segment is hoisted and installed in two layers by derrick crane,which is an innovative steel truss girder installation method after the individual element assembly method,truss block installation method and integral segment installation method.