Analysis of building frames with viscoelastic dampers under base excitation

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