张靖皋长江大桥南航道桥锚体结构精细化分析

Refined Analysis of Anchorages of South Navigation Channel Bridge of Zhangjiagang-Jingjiang-Rugao Changjiang River Bridge

张靖皋长江大桥南航道桥为主跨2300 m的双塔双吊跨钢箱梁悬索桥,南、北锚碇采用巨型重力式锚碇,通过后张预应力体系将拉力为7万吨级的主缆锚固在锚体上,锚体结构受力复杂。为指导南航道桥锚体结构设计,以主缆水平分力较大的南锚碇为例,根据设计需求对其开展精细化分析,并给出相应的设计建议。基于锚体的2种控制工况(预应力张拉阶段工况及主缆拉力作用阶段工况),采用有限元软件建立1/2南锚碇有限元模型与中央索股面切块有限元模型,分析锚体的总体、局部及底面应力的分布规律;提出基于主应力迹线和边界面应力分布的力流分析方法,分析锚块内部的主要拉、压力流路径。结果表明:锚体总体应力水平较低,后锚面锚固区及后锚室上、下两侧存在拉应力集中,且后锚室的前方底面存在较大的剪、拉应力组合;后锚面上、下两侧及锚块尾端区域存在较大拉力流。据此给出了延长前、后锚面锚固区钢筋及加密后锚室前方底面的竖向钢筋等配筋构造设计建议。

The south navigation channel bridge of Zhangjiagang-Jingjiang-Rugao Changjiang River Bridge is a two-tower,steel box girder suspension bridge with a main span of 2300 m,featuring two unequal suspended spans.The main cables of 70000-t tension force are anchored to the giant south and north gravity anchorages via the posttensioned prestressing systems.The mechanical behaviors of the anchorage bodies are complex.To direct the anchorage structure design of the south navigation channel bridge,the south anchorage exhibiting greater horizontal component was selected for refined analysis in accordance with the design requirements,and the design suggestions were given.A finite element model of a half of the south anchorage and a slice model along the central cable strands were established to analyze the distribution characteristics of the stresses in the entire anchorage as well as in the local zones and bottom of the anchorage,considering two loading scenarios(prestress tensioning stage and main cable tensioning stage).A force flow analysis method that is developed based on the principal stress trajectory and boundary stress distribution was proposed,by which the trajectories of principal tensile and compressive forces inside the anchorage were analyzed.It is shown that the overall stress level of the anchorage was low,stress concentrations were observed in the anchor zones of the rear anchor surface as well as the top and bottom sides of the rear anchor surface,and significant shear and tensile stress combinations existed in the bottom of the front of the rear anchor chamber.Moreover,substantial tensile force flow was found in the top and bottom sides of the rear anchor surface as well as the end zones of the anchorage.It is recommended to extend the reinforcement in the front and rear anchor surfaces and add more vertical reinforcement in the bottom of the front of the rear anchor chamber.