某斜靠式拱桥施工期主梁变形分析及处理

Cause Analysis of Main Girder Deformation of a Leaning-Type Arch Bridge in Construction Stage and Treatments

某斜靠式钢拱桥为3跨连续梁拱组合体系,跨径布置为(14.9+82.2+14.9)m,位于软土地基上。施工顺序为先梁后拱,主梁采用钢管支架法施工,主梁安装完成后,发生了中跨主梁下陷、边跨主梁上翘的现象。通过力学和有限元分析,得出中跨主梁下陷的主要原因是地基沉降,边跨主梁上翘的主要原因是白天高温时段安装。针对变形原因,对中跨主梁采用了临时支墩顶升优先、吊索上拉备用的处理措施,对边跨主梁采用了“配重下压、中跨顶升”的综合措施,并结合处理措施调整了施工工序。经过处理后主梁成桥高程误差满足规范要求,处理措施有效、得当。

A leaning-type arch bridge is a combined continuous beam and arch bridge with three spans of 14.9,82.2 and 14.9 m.The foundations of the bridge stand on soft strata.The main beam was constructed using steel tubular scaffolds,ahead of the construction of arch.When the installation of main beam was finished,downwarping and upwarping phenomena were observed in the central span and side spans,respectively.The mechanical analysis and finite element analysis proved that the downwarping of main beam in central span was caused by foundation settlement,and construction in the high temperature period during day time resulted in the upwarping of main beams in side spans.To address these issues,temporary supports were installed to jack up the main beams in the central span,with lifting ropes as the back-up measure.Whereas,the side spans were counterbalanced and pressed downwardly,together with jacking in midspan,and the construction procedure was adjusted accordingly.After being treated,the elevation error of the superstructure met the code requirements,proving that the measures taken were effective and proper.