中文摘要：

为了更深入探寻斜拉桥极限跨径，快速计算出不同拉索布置型式的大跨斜拉桥主梁轴力，文章基于密索斜拉桥索膜假定，求解出拉索在主塔上的位置方程，并推导出恒活载作用下扇形体系斜拉桥主梁轴力实用公式，给出简化的辐射式、竖琴式拉索布置的斜拉桥主梁轴力公式，且与丹麦学者Gimsing、我国学者王伯惠的轴力公式进行对比及算例验证。研究结果表明：3种近似计算公式与有限元结果基本吻合，该文公式求解的主梁轴力与有限元解误差更小，主要原因是索塔及跨中处的主梁无索区长度在公式推导过程中亦得到充分考虑。该公式能满足概念设计阶段的要求，适用于大跨斜拉桥轴力的快速近似计算。

英文摘要：

In order to explore the limit span of cable-stayed bridge, calculate out the axial force of the girder of long-span cable-stayed bridge with different cable arrangement types quickly, the position e- quation of the cable in the main tower is solved based on the cable-membrane assumption of cable- stayed bridge with multiple cables, the axial force formula of the girder of fan system cable-stayed bridge under the live load and dead load was derived based on the modified cable-membrane method, and the formula of axial force of the girder of cable-stayed bridge with the radiation and harp arrange- ment is simplified. Then the formula is compared with the axial force formula from Danish scholar Gimsing and Chinese scholar Wang Bohui and verified with examples. The results show that three ap- proximate formulas are in agreement with the results of finite element method, the error of the formu- la in this paper is smaller because the lengths of the girder without cables on mid-span and bottom of pylon towers are fully considered in the formula. The presented formula can meet the requirements of the conceptual design, and it is suitable for the axial force calculation of long-span cable-stayed bridg- es.