跨中交叉布索的多塔斜拉桥受力机理及参数分析
The stress mechanism and parameter analysis of multi-tower cable-stayed bridge with crossed cables

为解决多塔斜拉桥整体刚度不足的力学缺陷，研究跨中交叉布索多塔斜拉桥的力学特性，分析交叉索的作用机理，得出交叉索作用下中塔抗推刚度的理论公式，并以昆斯费里大桥为依托工程，通过改变跨中交叉拉索对数进行各方案的有限元分析，研究交叉索参数对结构刚度的影响程度及规律。研究结果表明：跨中交叉拉索使主梁挠度减小，结构整体刚度增大；在50 kN/m的不平衡荷载作用下，设置6对交叉索使中塔水平位移减小约28.63%，边塔水平位移减小约14.16%，跨中挠度减小约13.26%，主梁最大正弯矩减小约29.80%，主梁最大负弯矩减小约17.41%；多塔斜拉桥整体刚度随交叉索数量的增加而增大，但刚度增大趋势逐渐减缓。
In order to solve the mechanical defects of insufficient stiffness of multi-tower cable-stayed bridge, this paper explored mechanical properties of multi-tower cable-stayed bridge with crossed cables and analyzed stress mechanism of the crossed cables, and then obtained an analytic formula for calculating the longitudinal restraint stiffness of the middle tower of multi-tower cable-stayed bridge with cross stays. According to the Queensferry Crossing as a project case, the finite element analysis of many contrast schemes is established by changing the quantity of the crossed cables and the influence degree and regularities of structural rigidity with crossed cables is investigated. The results show that crossed cables can make the beam deflection decreases, thus increasing the overall stiffness of the cable-stayed bridge; under unbalanced loads of 50 kN/m, the displacement of middle tower reduces about 28.63% after setting 6 pairs crossed cables, at the same time, the displacement of edge tower is 14.16%, the reduction of mid-span deflection is 13.26%, the reduction of maximum positive moment and negative moment of main beam are 29.80% and 17.41% respectively; The overall stiffness of the multi-tower cable-stayed bridge increases with the increase of the number of cross cables, but the stiffness increase trend gradually slows down