G3铜陵长江公铁大桥桥塔设计

Design of Towers of Tongling Changjiang River Rail-cum-Road Bridge Carrying a Section of G3 Expressway

G3铜陵长江公铁大桥主桥为主跨988 m斜拉-悬索协作体系桥。江北、江南侧桥塔塔高分别为228.5、222.5 m,结构尺寸大,受力复杂,考虑桥塔受力、施工便捷性及主缆与斜拉索面协调布置等,确定采用C60混凝土门形桥塔。桥塔由上、下塔柱和上、下横梁组成,塔柱和下横梁为单箱单室截面,上横梁为开口槽形截面,索塔锚固区采用钢锚梁+混凝土齿块组合的索塔锚固结构,桥塔顶部主索鞍局部承压区采用间接钢筋网片加强并预留索鞍预埋件的布置空间。设计过程采用BIM技术优化局部设计细节,钢锚梁及钢牛腿等钢结构和混凝土结构外表面均采用防腐涂装体系进行耐久性设计。采用MIDAS Civil软件对桥塔整体受力进行分析,并对槽形断面上横梁基于经典理论、规范验算、实体有限元模型论证其结构安全性;基于ANSYS板壳有限元模型,研究不同板厚下钢锚梁锚下加劲板剪应力集中系数,以指导钢锚梁加劲板设计。桥塔塔柱采用支架法和爬模法施工,上、下横梁均采用支架法与塔柱异步施工。

The main bridge of Tongling Changjiang River Rail-cum-Road Bridge carrying a section of the G3 Expressway is a hybrid cable-stayed suspension bridge with a main span of 988 m.The south and north towers,which are portal-frame structures cast by C60 concrete,rise 228.5 and 222.5 m,respectively.The tower columns and lower crossbeam are of single-cell cross-section,while the upper crossbeam is of trough cross-section.The stay cables are anchored to the towers via a composite anchorage structure consisting of steel anchor beams and concrete wedges.Locally-compressed zones of the saddles on the top of the towers are strengthened with indirect reinforcement mesh and room is reserved for the pre-embedded components of the saddles.BIM is used to optimize local design details,and the surfaces of the steel anchor boxes and steel corbels as well as concrete structures are coated for corrosion protection.Global analysis of the bridge was carried out in MIDAS Civil.The structural safety of the upper crossbeam was verified by using classical theories,formulas suggested in specifications and solid-element finite element modelling.A shell-element model was developed in ANSYS to study the effects of plate thickness on shear stress concentration coefficient of the stiffening plates under steel anchor beams,to guide the design.The tower columns were cast using scaffolds and climbing formwork,while the upper and lower crossbeams were cast on scaffolds,unparallel with the tower column casting.