ANALYTICAL MODEL OF VISCOELASTIC DAMPERS FOR SEISMIC MITIGATION OF STRUCTURES

In order to mitigate the structural damage resulting from seismic load ing, viscoelastic dampers with high energy absorption capacity have be en applied to structures to enhance their seismic resistance. In order to simulate the material behavior of the viscoelastic damper, methods which only approximate the damping ratio induced by dampers were sugg ested in the past. Usually, it is difficult to find an adequate modulu s and strain to estimate the equivalent damping ratio since the nature of the material is not only greatly dependent on the frequency, but a lso on the strain ratio and the ambient temperature as well. These val ues are all varied in the presence of the hysteresis loops when the ma terial is subjected to a dynamic loading. In this paper, a constitutiv e equation for the viscoelastic damper was developed. This analytical model, based on fractional derivatives, is able to accurately describe the hysteretic behavior of a viscoelastic damper subjected to arbitra ry loadings. For the time-domain analysis, this model can be applied d irectly without transformation and inverse transformation to frequency domain, which usually causes computational difficulties. Results obta ined by the proposed model were in good agreement with available exper imental data.