Seismic effectiveness of direct and indirect implementation of MPD systems

This paper illustrates the advantages offered by inserting added viscous dampers into shear-type structures in accordance with a special scheme based upon the mass proportional damping component of Rayleigh viscous damping matrices, which is herein defined as MPD system. A comparison between the dissipative performances offered by the MPD system and a number of other systems of added viscous dampers (comprising classical and non-classical damping systems) is provided herein. The dynamic behaviour of direct and indirect implementation of the MPD system is checked through numerical time-history simulations for a 6-storey sheartype structure subjected to seismic excitations. The results, here obtained with reference to a number (40) of earthquake ground motions, confirm what previously found by the authors by using indexes based on the stochastic response and on the modal damping ratios: systems characterized by most dampers placed so that they connect each storey to the ground (as it is for the MPD system) display larger efficiency in energy dissipation than systems characterised by interstorey damper placement (traditional placement). This indicates that the efficiency of damping systems depends much more on damper placement rather than on damper sizing.