考虑塔梁影响的交叉索多塔斜拉桥中塔抗推刚度估算公式

为深入研究交叉索的作用机理,基于变形协调原理,忽略边塔水平小位移,推导了在塔、梁自身刚度影响下,交叉索对多塔斜拉桥中塔约束刚度的估算公式,并进行算例验证.研究结果表明:推导的公式解与有限元解的误差在8%以内,满足斜拉桥概念设计的精度要求.跨中交叉拉索可以使主梁挠度减小,进而提高多塔斜拉桥的整体刚度.多塔斜拉桥整体刚度随交叉索数量的增加而增大,设置10对交叉索后中塔位移减小量高达51%,但刚度增大趋势逐渐减缓.对于交叉索多塔斜拉桥而言,桥塔自身刚度的改变对中塔抗推刚度的影响大于主梁,但二者皆小于跨中交叉索对中塔抗推刚度的影响.

Estimation Formula for Longitudinal Restraint Stiffness of the Middle Tower of Multi-tower Cable-stayed Bridge With Crossed Cables by Considering the Effect of Tower and Beam

With the construction of Queensferry bridge in Scotland,the multi-tower cable-stayed bridges with crossed cables have entered the field of bridge engineers. In order to explore the action mechanism of crossed cables,considering the effect of tower and beam and ignoring the small level displacement of the side tower, based on the principle of deformation coordination, an analytic formula for calculating the longitudinal restraint stiffness of the middle tower of multi-tower cable-stayed bridge with crossed cables was deduced, and a numerical example was carried out. The results show that the error between the formula and finite element is within 8%, and it can meet the requirements of the conceptual design of cable-stayed bridge. Crossed cables can make the beam deflection decrease, thus increasing the overall stiffness of the cable-stayed bridge. The overall stiffness of multi-tower cable-stayed bridge rises as the number of crossed cables increasing.The displacement of middle tower reduction is up to 51% after 10 pairs of crossed cables are set, while the stiffness increase gradually slows down. The change of the stiffness of the tower's effect on longitudinal restraint stiffness of the middle tower for multi-tower cable-stayed bridge is greater than that of the main beam, but the crossed cables play more important roles in increasing the stiffness of the structure.