Effects of mechanical nonlinearity of viscoelastic dampers on the seismic performance of viscoelasticlly damped structures.

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. • A modified equivalent fractional Kelvin model with high prediction accuracy is established to depict the viscoelastic nonlinearity of VE damper. • An approximate method is devised to incorporate the effects of mechanical properties of VE dampers on the seismic response of VE structures. • The viscoelastic nonlinearity can introduce a negative effect on aseismic capacity of a VE structure, leading potentially risks to the structure. [ABSTRACT FROM AUTHOR]