矮塔斜拉桥塔跨比的优化研究

Research on Optimization of Tower Span Ratio of Low-pylon Cable-stayed Bridge

矮塔斜拉桥作为近几年一种新型的桥梁,它是在连续梁桥及常规斜拉桥的基础上逐步建立起来,其受力特性较好,目前得到广泛的运用。主要研究了在仅改变桥塔无索区高度的前提下,运用弯曲能量法对所有塔高模型进行成桥索力优化,并以塔高与主跨径之比为自变量,选取目标函数为因变量,运用数值分析软件进行曲线拟合,得到在此综合条件下塔高变化后的全桥受力特点及最优塔高。结果表明:桥塔高度的降低是以拉索索力的增大为代价的,本桥中塔高每降低5.5%,索力平均值增大约5%左右;综合塔梁固结处主梁弯矩、塔底弯矩、塔梁固结处主梁应力、塔底应力、拉索索量五种较为敏感的目标函数,得到该桥的最优塔跨比为0.138(约为1/7.2)。

As a new type of bridge in recent years,low-pylon cable-stayed bridge is gradually established on the basis of continuous girder bridge and conventional cable-stayed bridge.Its mechanical characteristics are good,and it has been widely used at present.In this paper,on the premise of only changing the height of the cable-free zone of the pylon,the bending energy method is used to optimize the cable forces of all the pylon height models.The ratio of the pylon height to the main span is an independent variable,the objective function is selected as a dependent variable,and the numerical analysis software is used to fit the curve of the pylon height to obtain the pylon height under this comprehensive condition.The mechanical characteristics and optimal tower height of the whole bridge after change.The results show that the reduction of tower height is at the cost of the increase of cable tension.For each 5.5%reduction of tower height in this bridge,the average increase of cable tension is about 5%.Five more sensitive objective functions are obtained,i.e.,the bending moment of the main girder,the bending moment of the bottom of the tower,the stress of the main girder,the stress of the bottom of the tower and the amount of cable at the consolidation of the tower girder.The optimal tower-span ratio of the bridge is 0.138(about 1/7.2).