塔梁分离式悬索桥动力及抗震性能

Dynamic and seismic performance of suspension bridge with separated girder and tower

针对塔梁分离式悬索桥具有塔底不等高及设置地锚索等特点,以矮寨桥为背景,基于9组空间有限元模型从主梁的支承条件、吊跨比以及地锚索的数量三个方面进行桥梁结构模态以及抗震性能分析.结果表明:在动力特性方面,塔梁分离对悬索桥振动模态影响十分微小,而吊跨比的增加会使悬索桥的整体刚度下降,加设地锚索能很大程度提高结构整体刚度;在抗震性能方面,塔梁分离提高了悬索桥横桥向的抗震性能,纵桥向基本无提升,随着吊跨比增大,主梁内力及位移响应减小幅度较大,而主缆和吊索内力几乎无变化,地锚索主要影响纵桥向地震响应,减小主塔位移与内力,降低了主缆与端部吊索的应力响应.

Aiming at the characteristics of suspension bridge with separated girder and tower,e.g.the unequal height at the bottom of tower and the layout of ground-anchored cable,and taking the Aizhai bridge as background,the modal and seismic performances of bridge structure were studied from three aspects,i.e.the support conditions of main girder,the ratio of suspension length to span and the number of ground-anchored cables,in accordance with nine sets of spatial finite element models.The results show that the separation of girder and tower has extremely minor influence on the vibration mode of suspension bridge in view of dynamic characteristics,whereas the increasing ratio of suspension length to span will reduce the overall stiffness of suspension bridge.Meanwhile,the adoption of ground-anchored cables can greatly improve the overall structure stiffness.In the aspect of seismic performance,the separation of girder and tower improves the seismic performance of suspension bridge in the transverse direction,but the longitudinal direction is basically not improved.As the ratio of suspension length to span increases,the internal force and displacement response of main beam decrease obviously,while the internal force of main cable and suspension is almost unchanged.The ground-anchored cables mainly affect the longitudinal seismic response of suspension bridge,reduce the displacement and internal force of main tower and lower the stress response of main and end cables.