The use of base isolation to protect a structure and its contents from earthquake damage has proven to be an effective anti-seismic strategy during past earthquakes. Modelling of the isolation system is one of the key steps in understanding the response of the structure and more importantly to evaluate the effectiveness of the isolation system. This paper presents a study on the effect of damping in an isolation system using a linear spring and linear viscous damper to model the response of the isolated superstructure. Although this model may not be representative of the mechanical behaviour of a real isolation system, most nonlinear systems can be linearised in some form to provide an estimate to the response and thus the use of this model in this study. From the floor response spectra of the roof mass, the increase in damping in the isolation system leads to the excitation of response in higher modes. The floor response spectra also show that the effectiveness of isolation reduces with increasing damping in the isolation system and could be detrimental to the contents of the building. The bilinear model, also the basis of design codes such as the ASCE 7-16, is used in this study to model isolators. The analysis using the bilinear model with various design scenarios shows that the model delivers a significant amount of damping into the system when the system is experiencing regular intensity earthquake events. The presence of a high damping ratio in the isolation system, as in the linear model, excites the higher modes thus counteracts the objective of base isolating a structure. The paper concludes with a comparison of the isolator displacement estimated using the design code and the average response obtained through dynamic analyses. The difference between the displacement values is not large.

中文翻译：

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隔离系统中的阻尼对基础隔离系统性能的影响

在过去的地震中，使用基础隔离保护结构及其内容物免受地震破坏已被证明是一种有效的抗震策略。隔离系统的建模是了解结构响应的关键步骤之一，更重要的是评估隔离系统的有效性。本文介绍了在使用线性弹簧和线性粘性阻尼器对隔离的上部结构的响应进行建模的隔离系统中的阻尼效果的研究。尽管此模型可能不能代表实际隔离系统的机械性能，但大多数非线性系统可以某种形式线性化以提供对响应的估计，从而可以在本研究中使用此模型。根据屋顶质量的地板响应光谱，隔离系统中阻尼的增加会导致较高模式下的响应激励。地板响应谱还表明，隔离的效果会随着隔离系统中阻尼的增加而降低，并且可能对建筑物的内容有害。本研究使用双线性模型（也是ASCE 7-16等设计代码的基础）对隔离器进行建模。使用具有各种设计方案的双线性模型进行的分析表明，当系统经历常规强度的地震事件时，该模型会向系统提供大量的阻尼。与线性模型一样，隔离系统中高阻尼比的存在会激发较高的模态，因此抵消了基础隔离结构的目的。本文对使用设计规范估算的隔离器位移与通过动态分析获得的平均响应进行了比较。位移值之间的差异不大。