Analysis of building frames with viscoelastic dampers under base excitation

A frequency domain response analysis is presented for building frames passi vely controlled by viscoelastic dampers, under harmonic ground excitation. Three different models are used to represent the linear dynamic force-defor mation characteristics of viscoelastic dampers namely, Kelvin model, Linear hysteretic model and Maxwell model. The frequency domain solution is obtai ned by (i) an iterative pseudo-force method, which uses undamped mode shape s and frequencies of the system, (ii) an approximate modal strain energy me thod, which uses an equivalent modal damping of the system in each mode of vibration, and (iii) an exact method which uses complex frequency response function of the system. The responses obtained by three different methods a re compared for different combinations of viscoelastic dampers giving rise to both classically and non-classically damped cases. In addition, the effe ct of the modelling of viscoelastic dampers on the response is investigated for a certain frequency range of interest. The results of the study are us eful in appropriate modelling of viscoelastic dampers and in understanding the implication of using modal analysis procedure for building frames which are passively controlled by viscoelastic dampers against base excitation.