多塔斜拉悬吊协作桥活载效应近似计算方法

根据斜拉-悬吊协作桥的受力特点,建立结构简化计算模型.基于悬索桥重力刚度理论,推导多塔斜拉-悬吊协作桥的悬吊部分在活载作用下的竖向位移表达式.针对多塔斜拉-悬吊协作桥的关键力学问题,应用推导出的竖向位移表达式,给出主梁最大活载挠度、塔顶纵向位移、主缆恒活载轴力和中塔主缆抗滑移系数等关键力学参数的估算公式.建立主跨为600,1 080和1 400m的三塔斜拉-悬吊协作桥和主跨为1 400m的二至六塔斜拉-悬吊协作桥有限元模型,较全面地验证所推导的公式.结果表明:对于三塔斜拉-悬吊协作桥,关键力学参数的最大误差为15%左右;对于四塔及以上斜拉-悬吊协作桥,关键力学参数的最大误差为20%左右.

Approximate Analysis Method of Multi tower Cable stayed Suspension Bridges Under Live Load

Based on the mechanical property of cable-stayed suspension bridges, reasonable and simplified model is established and the deflection expression of girder beam of multi-town cable-stayed suspension bridge under live load is deduced in view of the gravity stiffness theory of suspension bridge. After then, some approximate formulate, including maximum deflection of girder beam, displacement of the top of middle town, the axis force of main cable and the safety coefficient of restricting cable slide, etc., is given. In order to check the approximate formulate deduced in this paper, three-dimensional finite element model are established and analyzed with finite element software ANSYS. These models are some typical cable-stayed suspension bridge, including three bridges with three towns and different main spans, which are 600m, 1080m and 1400m, and four bridges with 1400m main span and different number of towns, which is three, four, five and six. The result of this investigation clarify that compared to the results of finite element analysis, the maximum error of the results of key mechanics problem calculated by approximate formulate in this paper is less than 15% for three-town cable-stayed suspension, and it is less than 30% for more than four towns. Some correction factors are introduced to improve the precision of the approximate formulate.