Abstract: Based on a super-span cable-stayed bridge over Yangtze River,which is planned with two optional pylon foundation forms: caisson and pile,modal participating mass ratio distribution and modal period distribution of free structural vibration modes involving distinct horizontal participation of the under-pylon huge-mass pile caps are studied by contrast.Artificial ground motions are applied in linear time-history analysis to calculate the controlling seismic responses of the bridge structure with caisson-form pylon foundations and alternative pile-form ones,then the results of the two cases are compared at the same structural locations;and in the horizontal directions the contribution of the under-pylon huge-mass pile caps to the cap bottom seismic reactions are analyzed in time domain as well as frequency domain.The research indicates that participation of the under-pylon huge-mass pile caps in high-order structural vibration modes essentially influences the dynamic properties and seismic responses of the super-span cable-stayed bridge,and sharply magnifies the horizontal seismic foundation reactions at the pylon cap bottoms compared with the case of caisson-form pylons foundations,which increases the seismic vulnerability of the super-span cable-stayed bridge.

Key words: super-span cable-stayed bridge, pile foundation, caisson foundation, huge-mass pile cap, dynamic properties, seismic response

摘要： 以泰州过江超大跨斜拉桥为例,就主塔分别采用高桩承台基础和沉井基础两种形式,对比研究桩基础大质量承台参与结构高阶水平向振型的质量参与系数分布、周期分布等特点,输入人工地震动参数,针对两种主塔基础方案采用线性时程分析方法计算桥梁结构控制部位地震反应并进行比较,再就桩基础方案中大质量承台对承台底水平反力的贡献进行时域和频域分析。研究表明,与沉井基础相比,主塔桩基础大质量承台参与结构高阶振动对超大跨斜拉桥动力特性和地震反应有重要影响,特别对主塔基础水平反力有显著的倍增效应,增大了超大跨斜拉桥的地震易损性。

关键词: 超大跨斜拉桥, 桩基础, 沉井基础, 大质量承台, 动力特性, 地震反应