成昆铁路矮塔斜拉桥设计关键技术

成昆铁路攀枝花金沙江大桥采用跨径布置为(120+208+120)m的预应力混凝土矮塔斜拉桥。主梁采用变高度单箱双室预应力混凝土箱梁;桥塔采用H形钢筋混凝土结构,桥面以上塔高28m,塔高与跨径之比为1/7.5;斜拉索采用1 860MPa环氧涂层钢绞线,斜拉索穿过塔上分丝管索鞍后锚固于主梁上。该桥采用塔梁固结、墩梁分离的三摩擦副双曲面摩擦摆减隔震支座+剪力榫组合支承体系,不仅解决了桥梁的抗震,还有利于列车的平稳运行和梁端伸缩装置的设置;针对矮塔斜拉桥的特点,基于索梁活载比确定斜拉索索力和梁体预应力钢束的配置。对该桥进行车-桥耦合动力分析,分析结果表明桥梁的动力性能和列车过桥时的安全性与舒适性均满足规范要求。

Key Techniques of Design of Extradosed Cable-Stayed Bridge on Chengdu-Kunming Railway

The Jinsha River Bridge in Panzhihua City of Chengdu-Kunming Railway is a prestressed concrete extradosed cable-stayed bridge with spans of(120+208+120)m.Double-celled single-box prestressed concrete girder with variable heights is adopted for the main girder,and the H-shaped reinforced concrete structure is used for the bridge pylon,of which the height above the bridge deck is 28 m and the ratio of pylon height to girder span is 1/7.5,respectively.The stayed cables,which are made of 1 860 MPa epoxy-coated steel wires,are anchored to the main girder after passing through the split tube cable saddle area on the pylon.A system of"pylon-girder consolidation and pier-girder separation with three-friction double-spherical friction pendulum aseismatic bearing+shear tenon combined support"is adopted in the bridge,which not only solves the seismic problems of the bridge but also is favourable for the smooth running of trains and the setting of the beam-end expansion device.In accordance with the characteristics of extradosed cable-stayed bridges,the cable force and configuration of prestressed steel tendons of the girder are determined according to the live load ratio of the cable-girder.The vehicle-bridge coupling dynamic analysis of the bridge indicates that not only the dynamic performance of the bridge but also the safety and comfort of the train passing the bridge meet the requirements of the railway code.