Insertion of viscous dampers in Moment Resisting Frames (MRF)

This paper illustrates the results of a wide analytical and numerical study carried out in order to investigate the properties of the Interstorey (IS) positioning scheme for inserting added viscous dampers into Moment-Resisting-Frame (MRF) systems. In order to evaluate the damping properties of these (non classically damped) systems the complex notation was adopted. A specific validation test is here proposed in order to confirm the applicability of this approach. In the paper a simple analytical formulation (based on physical principles) is presented in order to obtain an estimation of the damping properties of an MRF system on the basis of the properties of both the structural system and the ensemble of added viscous dampers. The applicability of the proposed procedure was validated through the development of a number of numerical simulations with reference to linear elastic MRF systems with number of storeys ranging from two to six and equipped with various systems of added viscous dampers. The findings, developed with particular reference to civil structures, provide useful principles also for the effective addition of viscous dampers in mechanical dynamic systems subjected to base (earthquake) excitation.