The Aizhai Bridge in West Hunan is a suspension bridge with separated towers and girder and with span arrangement of the main cables of 242 m+1176 m+116 m. In the design of the bridge, the schemes of the regular suspension bridge and the suspension bridge with separated towers and girder of high and low alignment sites were compared and finally the scheme of the suspension bridge with separated towers and girder that had less excavation amount in the mountain massif and that was cost-saving and structurally rational was chosen in the light of the special topographic and geological conditions at the bridge site. The way of adding the auxiliary anchor cables to the bridge satisfactorily resolved the problem of incompatible deformation between the main cables and stiffening girder caused by the too long area of the structure without suspenders. The software FLAC3D was used to analyze the stability of the structural system and mountain massif and the stability technique for the structural system and mountain massif was thus formed. The software MIDAS Civil was used as well to set up the spatial link finite element models for the structure and to analyze the static and dynamic performance of the structure. The results of the a-nalysis show that the global stiffness of the suspension bridge with separated tow-ers and girder in the vertical, transverse and longitudinal directions is greater than that of the regular suspension bridge, the dynamic performance of wind resistance of the former is good and accordingly the sizes of expansion joints can be greatly reduced.%湘西矮寨大桥为塔—梁分离式悬索桥,主缆跨径布置为242 m+1 176 m+116 m.设计过程中对高线位、低线位常规悬索桥方案和塔—梁分离式悬索桥方案进行比选,结合特殊的地形、地质条件最终选择了山体开挖量小、经济性好、结构合理的塔—梁分离式悬索桥方案.采用增设辅助锚索的方法较好地解决了该结构无吊索区长度过长造成的主缆和主梁变形不协调的问题.采用FLAC3D软件分析结构体系与山体的稳定性,形成了结构与山体系统稳定技术.采用MIDAS Civil建立结构空间杆系有限元模型,对其静、动力性能进行分析,分析结果表明:塔—梁分离式悬索桥的竖向、横向以及纵向的整体刚度均比常规悬索桥大,抗风动力性能较好,可较大地减小伸缩缝规模.
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