远场长周期地震下桩-土-层间隔震结构体系的灾变机理与失效控制

The relevant regulations and design methods of the mid-story isolationtechnology used in deep soft soil site are not involved in the domestic andforeign codes for seismic design of buildings. After the amplification by the deep soft soil site, the long-period components of the far-field ground motion will become long-periodpulse motions characterized by a plurality of cycle pulse, which are similar tothe harmonic ground motions. Long-period mid-story isolated structures may causeserious damage when subjected to these long-period pulse motions. Thus, all of these coupling mechanism, disaster mechanism, failure mode and failure control strategy of mid-story isolated structures considering the soi-pile-structureinteraction are the key to resistance. To this end, considering the soi-pile-structure dynamic interaction, a three-dimensional model of the mid-story isolated structure is established, in which the dynamic contact and separation between soil and pile, soil and pile capare taken into account. The vibration characteristics and interaction mechanism of the soil-pile-isolation system under the condition of different soil sites are revealed. Then, a simplified analytical modelis set up to consider the effect of the soil-pile- isolation system. On the basis of the above studies, the disaster mechanism and failure mode of thesoil-pile-isolation system when subjected to far-field long-period ground motionare explored. Control strategies for structure-failure, such as soft limitingdeformation of isolation layer and combined isolation in middle story, areproposed. In the end, all the above-mentioned will be validated by shaking table tests of a isolated structure model. The findings of this study would provide scientific basis for the seismic design of mid-story isolated structures in deep soft soil site.

国内外建筑抗震设计规范对处于深厚软弱地基上的结构采用层间隔震技术的相关规定和设计方法尚未涉及；远场地震动的长周期成分经过深厚软弱土层放大后，产生多个循环的长周期脉冲，类似谐波振动，对周期较长的层间隔震结构可能引起严重破坏。为此，研究远场长周期地震下桩-土-层间隔震结构体系的动力耦合作用机理、灾变机理、失效模式及失效控制，是进行其抗失效设计的关键问题。考虑桩与土、土与承台动态接触与分离现象，建立桩-土-层间隔震体系动力相互作用的三维分析模型；揭示软弱土层条件下桩-土-层间隔震体系的振动特征及相互作用机理；建立能够考虑桩—土—结构动力相互作用效应的桩-土-层间隔震体系的整体简化分析模型。在此基础上，探究远场长周期地震下桩-土-层间隔震体系的灾变机理与失效模式，研究隔震层软限位与层间组合隔震结构失效控制策略，并对上述结果进行振动台试验验证。为层间隔震结构在深厚软弱地基上的应用提供充分的理论依据。

考虑桩-土-结构相互作用（SSI）改变了结构体系动力特性，导致刚性假定的结构体系无法体现出良好的减震效果。历次地震表明，远场长周期地震动低频成分丰富，会使高层、隔震建筑等长周期结构体系产生较大位移响应，考虑SSI效应后可能会产生更为不利的影响。为此，研究远场长周期地震下桩-土-层间隔震结构体系的动力耦合作用机理、灾变机理、失效模式及失效控制，是进行其抗失效设计的关键问题。提出了远场长周期地震动的识别准则并筛选了后续试验研究的地震动记录，从反应谱、傅里叶谱角度分析了远场长周期与普通地震动的差异性。揭示软弱土层条件下桩-土-层间隔震体系的振动特征及相互作用机理；建立能够考虑桩—土—结构动力相互作用效应的桩-土-层间隔震体系的整体简化分析模型。以此为基础，探究远场长周期地震下桩-土-层间隔震体系的灾变机理与失效模式，研究隔震层软限位与层间组合隔震结构失效控制策略，进行了多种参数下的振动台试验验证。