多跨连续梁拱组合体系桥梁施工关键问题研究

摘要

安康市城东汉江大桥主桥为(75+2×125+160+2×125+75) m多跨连续梁拱组合体系桥梁,全桥采用先梁后拱法施工,系梁采用平衡悬臂浇筑法施工,中跨跨中33 m梁段采用支架现浇法施工.为选择合理的现浇段支架拆除时机、边跨配重卸载时机、临时固结拆除顺序以及吊杆张拉顺序和次数等,采用MIDAS Civil建立全桥有限元模型,针对各种方案下的结构进行模拟分析.结果表明:跨中现浇段的支架应在张拉完全部吊杆后再拆除;边跨配重应在中跨或次边跨合龙后再卸载;应待相邻孔合龙后再拆除前一合龙孔的临时固结;应对称交替地张拉吊杆,设计张拉力较小时可一次张拉到位,设计张拉力较大时应分批张拉到位.该桥采取以上方案施工后,结构受力状态良好.%The main bridge of the Chengdong Hanjiang River Bridge in Ankang City is a hybrid system bridge of multi-span continuous girder and arches with span arrangement (75+2×125+160+2×125+75) m.The whole bridge of the bridge is constructed,using the method of constructing the girder before constructing the arches,of which the tie girder is cast in situ,using the free cantilever method and the 33 m long girder segments at the midspan of the central span are cast in situ,using the scaffolding method.In the construction of the bridge,to choose the reasonable time for removal of the scaffolding for the cast-in-situ segments,the time for unloading of the counterweight on the side spans,the sequences for removal of the temporary rigid fixity and the sequences and times for tensioning of the hangers,the MIDAS Civil was used to establish the finite element model for the whole bridge and the structure under the different schemes was simulated and analyzed.The results suggest that the scaffolding for the cast-in-situ segments at the midspan of the central span should be removed after the whole hangers are well tensioned.The counterweight on the side spans should be unloaded after the central span or the secondary side spans are closed.The temporary rigid fixity for the previous closed span should be removed after the adjacent spans are closed.The hangers should be tensioned symmetrically and alternatively.For the hangers with little designed tension,the hangers should be tensioned in place in one time while for the hangers with great designed tension,the hangers should be tensioned in place in batch.With the above mentioned different schemes,the force conditions of the structure after the construction have been so far so good.