地锚式独斜塔混凝土斜拉桥抗震性能

Seismic behavior of concrete ground-anchored cable-stayed bridge with inclined tower

为探讨单跨独塔斜拉桥在地震荷载作用下的受力状况,以国内某单跨地锚式独斜塔混凝土斜拉桥为背景,采用MidasCivil 2019有限元软件建立全桥三维有限元模型,研究地震动方向和阻尼比对斜拉桥主梁和桥塔的弯矩和位移时程响应的影响。研究结果表明:斜拉桥的整体刚度较柔,其主梁在前2阶模态中主要表现为竖向弯曲,应重点关注斜拉索受拉断裂问题。在纵桥向地震波激励下,塔底弯矩最大,易引起混凝土开裂;竖桥向地震动对主梁跨中变形的影响最大,对塔底和主梁弯矩的影响最小,而横桥向地震动对塔顶变形的影响最大。阻尼比降低,主塔和主梁的弯矩和位移地震响应明显提高。合理设计结构的阻尼比,可以有效改善主梁和桥塔的地震响应,提高结构的抗震性能,可为工程抗震设计与计算提供参考。

To study the stress state induced by seismic load of single span single tower cable-stayed bridge,the three-dimensional finite element model was established using the Midas Civil 2019 software based on a single-span ground-anchored concrete cable-stayed bridge with single and inclined pylon.The effects of ground vibrations and damping ratios on the bending moment and displacement seismic time-history responses of the girder and the tower were studied.It was showed that the global rigidity of cable-stayed bridge was relatively low,the significant vertical bending could be found in the girder in the first 2 orders of natural vibration modes.Consequently,the critical attention should be played to the cable tensioning caused by the bending vibration of girder to avoid the breaking of cables.When the seismic wave was input in the longitudinal direction,the maximum bending moment of the tower was induced at the bottom,causing the concrete cracking easily.The vertical seismic load had the maximum effect on the deformation of the girder in the mid-span,and the minimum effect on the bending moments of the tower at the bottom and girder.The horizontal seismic load had the maximum effect on the deformation of tower top.The reduction of damping ratio had the significantly increasing effect on the time-history responses of bending moments and displacements of the tower and the girder.In the seismic design,the damping ratio should be designed reasonably to effectively improve the seismic responses of the girder and tower,and enhance the structural seismic performance.The research results can provide reference for the seismic design and the calculation of related project.