【作者】 韩军；

【导师】 李英民；

【作者基本信息】 重庆大学 ， 防灾减灾工程及防护工程， 2004， 硕士

【摘要】 长期以来,建筑结构抗震设计中的地震反应分析多采用刚性地基假定,计算模型常仅考虑上部结构,地震动输入采用自由场地表地震动。对于带深桩高层建筑结构,结构输入将大大有别于自由场地震动,基于刚性地基假定下的常规地表地震动输入法需仔细讨论。本文围绕带深桩基础高层建筑结构地震动输入问题,对土-结构动力相互作用进行了综述;进行了ANSYS动力有限元分析参数及模型的验证;进行了自由场地震反应分析;对常规输入法和整体有限元法计算出的结构地震响应进行了对比分析;基于反应谱法分析对常规输入法的计算误差进行了初步估计。研究得到的主要结论有:① 桩-土-结构整体模型的自振周期比刚性地基假定下的上部结构模型的自振周期要延长,且场地土越软,自振周期延长越多;同一类场地上结构越高,周期延长的幅度越小;场地覆盖土层厚度和等效剪切波速相近(即属于同一类场地)的单层土上整体模型比刚度随深度逐渐增大的多层土上整体模型的周期放大系数小;② 常规地震动输入法计算所得的地震作用、内力和变形多数情况下比整体模型基岩输入法计算所得的要大,且场地土越软这种趋势越明显;③ 常规输入法误差系数沿楼层分布形状随楼层高度增加而变复杂;④ 常规输入法的误差主要受输入基岩波的频谱特性、自由场地表反应地震动的频谱特性、常规模型上部结构的前几阶特别是第1阶自振频率和整体有限元模型的前几阶特别是第1阶自振频率等四个方面因素的影响;⑤ 总体上讲,常规输入法偏安全,是基本可行的,但对于结构底部几层的层间位移、柱上端弯矩、中间跨梁端弯矩(剪力)和边跨梁端弯矩(剪力)等常偏不安全,对于边柱轴力和中柱轴力沿楼层全高常偏不安全,对此应引起足够重视,且在结构底部等关键部位宜对常规输入法计算所得的内力和变形值进行调整。本文最后分析了目前研究的不足,并对后续工作提出了建议。更多还原

【Abstract】 For a long time, the rigid ground assumption has been used for earthquake response analysis in the seismic design in which only superstructure is considered in the model and the free field surface input of ground motion is adopted. However, as for the case of tall building with deep pile foundation, the structural input would be highly different from free field ground motion, so the conventional method of surface ground motion input based on rigid ground assumption needs further and detailed examination.Centered on the problem above, this paper first contains a review about the research of pile-soil-superstructure interaction, then a verification of parameters and model is made by using ANSYS LS-DYNA, we made a free field earthquake response analysis and a comparison between conventional input and integral finite element method results of structural earthquake response, based on response spectrum analysis we also made a estimation about the error of conventional input.Below are the conclusions:The natural vibration period of the pile-soil-superstructure integral model is longer than that of the superstructure model based on rigid ground assumption, the gap enlarges with the softness of the field soil and diminishes with the height of the building. The natural vibration period increment in the integral model on single layer soil with similar thickness and equivalent shear wave velocity is smaller than that in the model on multi-layer soil whose rigidity increases with depth.Earthquake response, inner force and deformation from conventional input method are higher than those from integral bedrock input method; the gap enlarges with the softness of the field soil.The distribution shape of the error with storey becomes more complex with the increasing of the storey number.There are mainly 4 influencing factors for the error of the conventional input method: the spectrum characteristic of the bedrock wave input, the spectrum characteristic of the free field ground earthquake response, the natural frequency of first a few order especially primary natural frequency of the conventional and the integral finite element model.The conventional input method is reliable and feasible in most cases, but at the lower part of the building, the story drift, the moment at the upper end of the <WP=7>columns, the moment and shear force at the end of the beams located at middle and side spans lack enough reliability, the same case happen the axial force in all middle columns and side columns, which demands special attention and requires adjustment on the results from conventional input method.At the end of the paper we made a summary about the deficiency of present research and perspectives of subsequent study.更多还原