Vibration modes and equivalent models for flexible rocking structures
Vibration modes and equivalent models for flexible rocking structures
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DOI：
10.1007/s10518-017-0128-4
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发表时间：
2017-04
影响因子：
4.6
通讯作者：
S. Acikgoz;M. DeJong
中科院分区：
文献类型：
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作者：
S. Acikgoz;M. DeJong
预测柔性摇摆结构在地震动作用下的位移和力响应对结构的评估和设计具有重要意义。尽管很实际，但使用简单的力学模型来进行这些预测是可取的。然而，摇摆和振动之间的复杂耦合使得使用简单模型进行准确预测变得困难。本文研究了用半耦合等效模型来近似刚性地基上多质量体结构的摇摆动力响应。这些等效模型具有两个自由度的耦合摇摆振荡器来描述摇摆和第一模式的振动的相互作用，和非耦合线性弹性振荡器来描述更高模式的振动响应。为了评估这些等效模型，首先确定多质量结构的动态响应的模态分量。这些部件突出了冲击时振动模式激发的关键影响。然后，通过比较等效模型模拟与最近的振动台试验和多质量分析模型模拟，进行了进一步的调查。这些比较表明，等效模型可以准确地捕捉摇摆响应的一个现实的位移范围内，如果一个新的地面加速度标度项被采用。然而，非耦合线弹性振子不考虑冲击激励，因此，等效模型不能充分捕获加速度响应。因此，在分析识别的模态分量的基础上，提出并验证了改进等效模型加速度预测的进一步修改。
Predicting the displacement and force response of flexible rocking structures to ground motion is important for their assessment and design. Insofar as practical, it is desirable to use simple mechanical models to make these predictions. However, the complex coupling between rocking and vibration makes accurate predictions with simple models difficult. In this paper, the use of semi-coupled equivalent models to approximate the dynamic response of multi-mass structures rocking on rigid ground is evaluated. These equivalent models feature a two-degree of freedom coupled rocking oscillator to describe the interaction of rocking and the first mode of vibration, and uncoupled linear elastic oscillators to describe higher mode vibration response. To evaluate these equivalent models, the modal components of the dynamic response of multi-mass structures are first determined. These components highlight the critical influence of the excitation of vibration modes at impact. Then, further investigations are carried out by comparing equivalent model simulations to recent shake table tests and multi-mass analytical model simulations. These comparisons reveal that the equivalent models can capture the rocking response accurately for a realistic range of displacements, if a new ground acceleration scaling term is adopted. However, the uncoupled linear elastic oscillators do not consider excitation at impact and consequently, the equivalent models do not capture the acceleration response adequately. Therefore, on the basis of the analytically identified modal components, a further modification that improves the equivalent model acceleration predictions is proposed and validated.