无背索斜拉桥稳定分析的能量法

无背索斜拉桥在理想的成桥状态下,面内失稳模态为主梁屈曲。将主梁简化成弹性地基梁计算模型,选用正弦级数作位移函数,运用能量方法,提出了主梁屈曲临界荷载的计算公式。结合该类桥梁的结构布置特点,用简洁的连续函数描述主梁轴压力和拉索弹性支承刚度的变化,同时用简单的线形折减系数反映斜塔变形对拉索弹性支承刚度的影响。最后以长沙市洪山大桥为例,用该方法计算了其成桥状态屈曲临界荷载,其结果与有限元解对比具有很好的精度。

ENERGY METHOD FOR STABILITY ANALYSIS OF CABLE-STAYED BRIDGE WITHOUT BACKSTAYS

For cable-stayed bridge without backstays under ideal completed stage, the in-plane instability of the structure many occur in the form of girder buckling. A formula based on energy method is proposed to calculate the critical buckling load of the main girder, adopting elastic foundation beam simplification and selecting the sine series as the displacement functions. According to the structural characteristics of this type of bridge, the simplified continuous functions are developed to describe the variations of the axial force of the girder and the equivalent elastic supporting stiffness of the cable. Moreover, the linear discount coefficient is introduced to account for the effect of pylon deformation on supporting stiffness. A case study on the critical load of Hongshan Bridge in Changsha is finally conducted for verification. The results are in good agreement with those of the finite element method.