Analysis of building frames with viscoelastic dampers under base excitation

A frequency domain response analysis is presented for building frames passively controlledby viscoelastic dampers, under harmonic ground excitation. Three different models are used to representthe linear dynamic force-deformation characteristics of viscoelastic dampers namely, Kelvin model, Linearhysteretic model and Maxwell model. The frequency domain solution is obtained by (i) an iterativepseudo-force method, which uses undamped mode shapes and frequencies of the system, (ii) anapproximate modal strain energy method, which uses an equivalent modal damping of the system in eachmode of vibration, and (iii) an exact method which uses complex frequency response function of thesystem. The responses obtained by three different methods are compared for different combinations ofviscoelastic dampers giving rise to both classically and non-classically damped cases. In addition, theeffect of the modelling of viscoelastic dampers on the response is investigated for a certain frequencyrange of interest. The results of the study are useful in appropriate modelling of viscoelastic dampers andin understanding the implication of using modal analysis procedure for building frames which arepassively controlled by viscoelastic dampers against base excitation.