Seismic behaviour of asymmetric base isolated structures with various distributions of isolators
Seismic behaviour of asymmetric base isolated structures with various distributions of isolators
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DOI：
10.1016/j.engstruct.2008.12.006
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发表时间：
2009-04
影响因子：
5.5
通讯作者：
V. Kilar;D. Koren
中科院分区：
文献类型：
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作者：
V. Kilar;D. Koren
本文试图有助于更好地理解基础隔离不对称结构的行为。最初对称的四层 RC 框架建筑的许多变体均被视为测试示例，这些建筑由简单的铅橡胶支座底座隔离系统隔离，并具有各种隔离器分布。对称结构变体和适当的 LRB 轴承特性是根据欧洲规范 2 和 8 设计的。不对称变体是通过将质心 CM 移向建筑物的一侧而产生的。每个建筑变体的附加“扭转不受约束”和“扭转约束”子变体是通过改变质量分布获得的，而总质量和保持不变。对于基础隔震系统，我们考虑了六种不同的轴承分布，其特征是隔震器中心 CI 相对于上部结构的质心 CM 的位置。分析中包括两个对称（均匀和外围分布）和四个不对称分布的隔离器（称为 CI = CM、CI = CM/2、CI = −CM/2 和 CI = −CM）。本文分析了不同轴承分布对上部结构以及基础隔震系统的位移和旋转的正面和负面影响，并试图确定能够平衡引入的偏心影响的最有利的隔震器分布。 3D 非线性动态分析获得的结果以十种选定地面运动和三种不同比例的最大值的平均值表示。他们表明，所有六种考虑的轴承分布，无论如何不同，都大大减少了不利的扭转效应，这些效应不同程度地从上部结构转移到基础隔离系统。进一步观察到，常见建筑规范所青睐的 CI = CM 分布仅最适合适应基础隔离系统中的扭转效应。观察上部结构的非线性行为发现了一个显着不同的结论，其中 CI = CM 分布可能会对柔性侧框架造成更多损坏。
The paper tries to contribute to a better understanding of the behaviour of base isolated asymmetric structures. Numerous variants of originally symmetric four storey RC frame building isolated by a simple lead rubber bearing base isolation system with various distributions of isolators were considered as test examples. The symmetrical structural variant and appropriate LRB bearing properties were designed according to Eurocode 2 and 8. The asymmetric variants were produced by shifting the centre of mass CM toward one side of the building. Additional “torsionally unrestrained” and “torsionally restrained” sub-variants of each building variant were obtained by changing the mass distribution, while total mass sum remained unchanged. For the base isolation system we have considered six different distributions of bearings characterized by the position of the centre of isolators CI in respect to the centre of mass CM of the superstructure. Two symmetric (Uniform and Peripheral distribution) and four asymmetric distributions of isolators (called CI = CM, CI = CM/2, CI = −CM/2 and CI = −CM) were included in the analyses. The paper analyses the positive and negative effects of different bearing distributions to the displacements and rotations of the superstructure as well as to the base isolation system and tries to determine the most favourable distribution of isolators that is able to balance the effects of introduced eccentricities. The results obtained by 3D nonlinear dynamic analyses are presented as an average of maximums for ten selected ground motions and three different scalings. They indicate that all six considered distributions of bearings, however differently, substantially reduce the unfavourable torsional effects, which are with different extent transferred from the superstructure to the base isolation system. It was further observed that CI = CM distribution, favoured by common building codes, is best only for accommodating the torsional effects in the base isolation system. A significantly different conclusion was found observing the nonlinear behaviour of the superstructure, where CI = CM distribution might cause more damage in the flexible side frames.