The main navigation channels in coastal bay areas usually serve as main paths for sea vessels,which require high clearance to allow high-speed railway bridges to cross over.As high-speed railway requires very high performance of bridges,the economical practicality and technical feasibility of using large span for main navigation channel become a critical issue.With the background of a westbound channel with 100 million tons navigation capacity,this paper focuses on the analysis of two different structural plans:three-tower cable-stayed bridge with dual main spans of 460 m,and twin-tower cable-stayed bridge with a single main span of 812 m.After structural modeling,static force analysis and economical comparison,2 ×460 m three-tower cable-stayed bridge is recommended for the westbound channel.By conducting further analysis on structural behavior of the 2 × 460 m plan under static and dynamic force,this paper addresses critical technologies and solutions in three-tower cable-stayed bridge design,which include main girder structural formation,system stiffness control,thermal effects in long girders,cable stress and fatigue under dead load,wind resistance and etc.The study results show that the system stiffness of three-tower cable-stayed bridge is improved dramatically by means of steel-concrete composite girder for mid-spans,RC box girder for side spans,increasing mid tower and mid-span cable gravitational stiffness and fixed tower and girder system.As a result,the three-tower cable-stayed bridge for double-track railway is proved practical and economical.%沿海海湾主航道一般通行海轮,当高速铁路跨越海湾主航道时,为满足较高的通航净空标准需要采用大跨度铁路桥梁结构.由于高速铁路行车对桥梁性能要求高,主通航孔大跨度桥梁结构方案在技术及经济上是否合理可行成为值得重点研究的问题.结合沿海某海湾西航道通行10万t海轮的通航要求,重点研究双孔通航主跨2×460m三塔斜拉桥和单孔通航主跨812m两塔斜拉桥两种桥式方案.建立结构计算模型,对结构静力计算结果及技术经济指标进行综合对比分析,最后推荐西航道桥采用2×460 m三塔斜拉桥方案.进一步分析三塔斜拉桥结构主要静力动力结构行为,研究三塔斜拉桥结构设计中的主梁结构形式、体系刚度控制、主梁长联温度问题、拉索恒载应力与疲劳、结构抗风性能等关键技术的工程解决措施.研究表明:通过中跨采用钢混结合梁、边跨采用混凝土箱梁以及增大中塔及其两侧主跨斜拉索重力刚度和中塔采取塔梁固结体系等措施,能较大地提高三塔斜拉桥体系刚度,将三塔斜拉桥应用于高速铁路在技术经济上是合理可行的.对跨海湾大跨度双线高速铁路斜拉桥结构的设计研究具有一定的参考价值.
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