平潭海峡公铁两用大桥钢梁架设关键技术

Key Techniques for Erection of Steel Girders of Pingtan Straits Rail-cum-Road Bridge

平潭海峡公铁两用大桥通航孔桥钢梁标准梁段最重1 250t,80m梁重1 360t、88m梁重1 550t。平潭海域风大、浪高、大风频繁,根据现场施工条件,结合桥跨布置及现有设备,平潭海峡公铁两用大桥钢梁采用3 600t浮吊吊装及1 100t架梁吊机整节段悬臂拼装。钢梁浮吊架设时,在钢梁落梁节点下方设置落梁垫块和橡胶垫进行缓冲减震,以确保钢梁受力安全;钢梁快速吊装时采用了由纵(横)向撑杆、无接头绳圈和特殊钢梁吊耳组成的柔性吊具,降低了吊装中的安全风险;墩旁支架设计时充分考虑了钢梁的落梁偏差及冲击荷载的影响,并对柱头、柱脚等受力关键点进行了局部加强;利用桥塔墩固定支座和纵向阻尼器连接销座进行塔梁临时纵向限位,以抵抗钢梁悬臂架设期间的最大水平反力;通过设置简易抗风牛腿及利用主桥支座自身横向承载力,以抵抗钢梁悬臂架设期间的台风影响。

The heaviest standard segment of the steel girders of the navigable span bridges of the Pingtan Straits Rail-cum-Road Bridge is 1 250 t,the weight of the 80-m span steel girder is1 360 tand the weight of the 88-m span girder is 1 550 t.The wind in the Pingtan sea area is strong,the waves there are high and the area is frequently visited by the strong wind.In accordance with the site construction conditions of the bridges located in the area and in consideration of the span arrangement of the bridges and the available construction equipment,it was determined that the steel girders of the bridges would be lifted,using the 3 600 tfloating crane and would be cantileveredly assembled in integral segments,using the 1 100 tdeck cranes.At the time the steel girders were erected,using the floating crane,the padding blocks and rubber pads were arranged at the places under the points of the lowered girders so as to buffer the shock and to ensure the force condition safety of the girders.At the time the girders were rapidly lifted,the flexible slings consisting of the longitudinal（cross）struts,jointless loop ropes and special girder lifting lugs were used so as to reduce the safety risk in the lifting.In the design of the pier-side scaffoldings,the influences of the deviations and impact loads of the lowered girders were thoroughly considered and the critical load bearing points,such as the post heads and post footings of the scaffoldings,were locally strengthened.The connection pins of the fixed bearings and longitudinal dampers on the pylon piers were used to temporarily longitudinally limit the pylons and girders so as to resist the maximum horizontal reaction forces in the cantilever assembling and erection of the girders.By means of setting the simplified wind resistant corbels and making use of the transverse bearing capacity of the bearings themselves of the main girders,the influences of the typhoon in the cantilever assembling and erection could be resisted.