大跨轨道钢箱叠合梁桥顶推施工控制方法

Incremental Launching Construction Method for Long-Span Light Rail Bridge with Main Girder Composed of Steel Boxes and Concrete Slabs

为了寻求确保大跨度钢箱叠合梁桥顶推施工中线形和内力可控、成桥后满足设计要求的顶推施工控制方法,以大跨轨道钢箱叠合梁桥——重庆南纪门长江轨道专用桥北岸引桥为工程背景,采用MIDAS Civil软件建立空间有限元模型,结合无应力状态法理论,基于推导的数学公式,获取各钢箱梁节段控制点安装高程理论值,指导钢箱梁节段定位、安装,并给出误差计算公式,进行大桥顶推后钢箱梁线形评价;采用应力增量评价方法,进行大桥顶推后钢箱梁应力评价。结果表明:大桥线形、应力监测结果与理论值吻合较好;所提出的方法可指导钢箱梁精确定位安装,确保顶推施工过程中受力安全、线形可控,适用于类似工程顶推施工控制。

The incremental launching method plays an important role in ensuring the geometry and internal forces of the long-span bridge with main girder composed of steel boxes and concrete slabs during construction and in completed bridge state.In this study,the north approach of the Nanjimen Light Rail Bridge in Chongqing,which is a long-span bridge where the steel boxes and concrete slabs act compositely,is applied as a case.The spatial finite element model of the bridge was built by MIDAS Civil.Following the principle of stress-free state method,the theoretical installation elevations of controlling points on each steel box girder segment were calculated to direct the positioning and installation of the steel box girder segments based on the mathematical formula derived.The error calculation equations were derived for the rating of the geometry of the steel box girders after the incremental launching.The stresses in the steel box girder after incremental launching were assessed using the stress increment assessing method.The results show that the field monitoring data of the geometry and stresses of the bridge agree well with the theoretical values.The method proposed can guide the accurate positioning and installation of the steel box girders,which can ensure the safety of the structure during the incremental launching construction and can be recommended for the incremental launching construction control of similar projects.