中文摘要：

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1 400 m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.

英文摘要：

Based on the mechanical property of cable-stayed suspension bridges,a reasonable and simplified model is established and the deflection expression of girder beam of multi-tower cable-stayed suspension bridge under live load is deduced in view of the gravity stiffness theory of suspension bridge.Then,some approximate formulats are presented,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 and so on.In order to verify the approximate formulas,three-dimensional finite element models which are established,which are analyzed with finite element software ANSYS.These models involve typical cable-stayed suspension bridges,such as three-towered bridges with different main spans,which are 600,1 080 and 1 400 m,and the 1 400 m main-span bridges of different numbers of towers ranging from 2 to 6.In comparison with the results of finite element analysis,the result of this investigation clarifies the maximum error of the key mechanic parameters calculated by the proposed approximate formulas is within 15% for three-towered cable-stayed suspension,20% for bridges over four towers.