三塔悬索桥的结构体系及抗震性能研究

Structural system and seismic performance of three-tower suspension bridges

与通常采用的双塔悬索桥相比,三塔悬索桥因中间桥塔缺乏有效的纵向约束而导致结构整体刚度的下降,在地震作用下结构的动力反应问题可能会更加突出.以已建成的1 080m主跨的三塔双跨悬索桥-泰州长江公路大桥为工程背景,利用MIDAS/CIVIL有限元软件对其抗震性能进行分析,揭示了三塔悬索桥抗震性能的特点,在此基础上进行了主缆矢跨比、中塔刚度以及主梁约束方式等主要结构设计参数对大跨度三塔悬索桥地震反应的影响分析,并从抗震性能角度提出大跨度三塔悬索桥适宜的结构体系.研究结果表明:大跨度三塔悬索桥横桥向地震反应非常显著,尤其是边塔,因此应重视结构的横桥向和边塔的抗震性能.采用较大的矢跨比、柔性的中塔、中塔与主梁之间设置弹性索都可以有效地提高大跨度三塔悬索桥的抗震性能.

Due to the weak longitudinal restraint of the center tower, the structural stiffness of a three-tower suspension bridge is less than that of a two-tower suspension bridge, and therefore it becomes more susceptible to a seismic impact. By a case study of a three-tower suspension bridge-Taizhou Highway Bridge over the Yangtze River with two main spans of 1080 m, the seismic performance of the three-tower bridge was investigated by MIDAS/CIVIL finite element analysis. The jmpacts of 3 parameters, cable＇s sag to span ratio, the structural stiffness of the center tower, and the constraint conditions of main girder, on the seismic response of the bridge were also discussed. The optimised structural system was suggested with respect to seismic performance. The results show that the three-tower suspension bridge responds more violently to the transverse seismic action, especially in the side towers, This indicates that more attentions should be paid to the transverse seismic performance and the side towers. It is suggested that a large cable＇s sag to span ratio, a flexible center tower and the longitudinal elastic cable between the center tower and main girder are all favorable to improve structural seismic performance of a long-span three-tower suspension bridges.