Viscoelastic (VE) damper exhibits significant mechanical nonlinearity under dynamic loads due to variations in the temperature, excitation frequency, and the occurrence of large strains. However, in the existing research literature, such nonlinearity is barely considered, and its effects on the aseismic behaviours of viscoelasticlly damped structure (referred to as VE structures) are also unclear. In this paper, a modified equivalent fractional Kelvin model is established to depict the mechanical nonlinearity of VE damper with the introduction of internal variable parameters. Through the comparison with the existing mathematical models for the performance of an individual VE damper, it is found that the proposed model has a high prediction accuracy, especially in the large-strain working condition. To incorporate the effects of real-time change of the mechanical properties of VE dampers on the seismic responses of structures equipped with such dampers, an approximate method is devised for the numerical calculations. Two representative VE structure with proportionally and non-proportionally damped system are analysed with consideration of the time-varying mechanical nonlinearity of VE dampers. The discrepancy between the seismic responses of the VE structure with and without considering the nonlinearity is discussed. The results indicate that the mechanical nonlinearity of VE dampers could introduce a negative effect on the actual seismic resistance capacity of a VE structure, leading potentially to the structure not meeting the design requirements of codes when the mechanical nonlinearity occurs. The study concludes that it is necessary to take the mechanical nonlinearity into account in the design and performance evaluation of VE structures.

由于温度、激励频率的变化和大应变的发生，粘弹性 (VE) 阻尼器在动态载荷下表现出显着的机械非线性。然而，在现有的研究文献中，这种非线性几乎没有被考虑，其对粘弹性阻尼结构（简称VE结构）抗震行为的影响也不清楚。本文建立了一个修正的等效分数阶开尔文模型，通过引入内变参数来描述VE阻尼器的机械非线性。通过与现有的单个VE阻尼器性能数学模型的比较，发现所提出的模型具有较高的预测精度，尤其是在大应变工况下。为了将 VE 阻尼器的机械性能的实时变化对装有此类阻尼器的结构的地震响应的影响结合起来，设计了一种近似的数值计算方法。考虑到VE阻尼器的时变机械非线性，分析了具有比例和非比例阻尼系统的两种代表性VE结构。讨论了考虑非线性和不考虑非线性的VE结构地震响应之间的差异。结果表明，VE阻尼器的机械非线性会对VE结构的实际抗震能力产生负面影响，当机械非线性发生时，可能导致结构不满足规范的设计要求。