福州道庆洲过江通道主桥桥面系设计

Design of Main Bridge Deck System of Daoqingzhou River Crossing Passage in Fuzhou

道庆洲过江通道主桥采用双层变高预应力钢桁结合梁方案,腹杆为三角形桁架,主跨276 m,标准桁高9.5 m,支点附近桁高由9.5 m变高至23.0 m。道庆洲大桥为公轨两用桥梁,其结构最大的特点为跨度大,桁高矮,荷载重。为了分担部分主桁受力,主桥上层公路桥面系采用钢密横梁+混凝土板结合梁体系,混凝土板与钢横梁之间采用剪力钉进行连接,混凝土板的预应力钢束锚固于钢横梁上。下层轨道桥面系采用纵横梁+正交异性板整体桥面体系,端部压重区段采用箱体结构,内部灌注铁砂混凝土进行压重。对比现有工程中设置平弦和不设置平弦两种桥面系处理方式的优缺点,为满足三角形桁架结构的外观要求,下层轻轨桥面系在桁高变高位置处采用了创新形式的桥面结构,即多点支承式整体桥面系。此桥面系设置边纵梁,边纵梁及箱型横梁形成稳定的平面框架,并通过竖向支座支撑在主桁斜腹杆伸出的牛腿上,结构受力明确。在受力方面,对标准断面的上、下层桥面系作了详细的框架计算。结果表明结构刚度和应力均在规范要求的范围内。对比较突出的横梁扭转问题进行了深入分析,建立横向框架和局部有限元模型进行了结构安全性验证。针对主桁斜腹杆伸出的牛腿传力位置进行了精细化的结构有限元分析,验证了该部位各组成板件的应力符合规范要求,可保证本桥的结构安全。

The main bridge of the Daoqingzhou River Crossing Passage adopts a double-layer variable-height prestressed steel truss composite girder scheme.The web members are triangular trusses.The main span is 276 m,the standard truss height is 9.5 m,and the truss height near the fulcrum increases from 9.5 m to 23.0 m.This bridge is a dual-purpose bridge for road and rail,its biggest structure features are long span,low truss height and heavy load.In order to share part of the main truss forces,the upper road deck system of the main bridge adopts the composite beam system of steel dense beams+concrete slabs,the concrete slabs and the steel beams are connected by shear nails,the prestressed steel tendons are anchored on the steel beam.The lower track bridge deck system adopts the integral bridge deck system of longitudinal and cross beams and orthotropic slabs.The end weighting section adopts a box structure with iron sand concrete poured inside for weighting.Compared to the advantages and disadvantages of the bridge deck systems with/without flat chord in existing engineering,in order to meet the appearance requirements of the triangular truss structure,the lower light rail bridge deck system adopts an innovative form of bridge deck structure at the variable position of truss height(multi-point supported integral bridge deck system).The side longitudinal beams are set on the bridge deck system,the side longitudinal beam and box shaped crossbeam form a stable plane frame,which is supported on the corbels extended by the inclined web rods of the main truss through vertical supports with clear structural stress.In terms of stress,the detailed frame calculations are conducted for the upper and lower deck systems on the standard cross-section.The result shows that the structural stiffness and stress are within the requirements of the specification.An in-depth analysis on the prominent torsion of the crossbeam is conducted,and a transverse frame and local finite element models are established for structural safety verification.A refined structural finite element analysis on the force transmission position of the corbel extended by the inclined web rods of the main truss is conducted,which verified that the stress of each component of the plates at this position meets the requirements of the specification,and can ensure the structural safety of this bridge.