OPTIMAL INSERTION OF VISCOUS DAMPERS INTO SHEAR-TYPESTRUCTURES: SEISMIC PERFORMANCES AND APPLICABILITY OFTHE MPD SYSTEM

摘要

This paper provides illustrative examples regarding (a) the seismic performances offered by the MPDsystems when applied to shear-type structures and (b) the implementation of MPD systems in actualbuilding structures. As illustrated in a companion paper and in previous research works by the authors, theMPD system is an innovative system of added viscous dampers which is based upon the massproportional damping component of Rayleigh viscous damping matrices and is characterized by a highdissipative efficiency. The seismic performances of two shear-type structures equipped with severalsystems of added viscous dampers (including, in addition to the MPD system, other optimal dampingsystems identified using genetic algorithms and inverse problem approach) are compared throughnumerical time-history simulations. The results, here obtained with reference to 40 historically recordedearthquake ground motions, confirm that systems characterized by dampers placed so that they connecteach storey to a fixed point (as it is for the MPD system) display larger efficiency in energy dissipationthan systems characterized by interstorey damper placement (traditional placement). The results alsoindicate that the forces exerted through the dampers of the MPD system and of the other damping systemsconsidered are comparable in size. Two ways of implementing MPD systems in actual building structuresare also presented: direct implementation (dampers connect each storey to the ground) and indirectimplementation (dampers connect each storey of the base structure to a support structure: stiff verticalelement, e.g. the conventional concrete core of the stairs/elevator typically found in r.c. constructions).Numerical results indicate that (provided that the support structure is characterized by a relatively largelateral stiffness) direct and indirect implementations lead to similar damping effect on the base structurewithout increasing the dynamic actions upon the support structure. Illustrative examples for the technicalfeasibility of both direct and indirect implementations are also provided.