Seismic assessment of Isolator-Damper hybrid structural system based on analysis of MDOF and modal 2DOF models

Abstract

A hybrid structural system is introduced and assessed; by combining two widely used passive devices, isolator and damper, along with the use of the partial plan isolation technique in the conventional buildings. Four partial isolation cases in comparison with three limit cases including a full-base fixing, full-base isolating and ideal story damping (Skyhook) are used on a finite element model of a 12-story building. The mentioned four cases have been selected by changing the number of fixed and isolated columns which caused isolated mass ratio between 28% and 71%. Also, a simplified manifest of the seismic performance of this proposed hybrid system is presented in the form of a 2DOF model. Time history analyzes under far- and near-faults earthquakes, frequency analysis and stationary random analysis under white noise are performed. Various structural actions are investigated, including the root mean squares (rms) and maximum of drift, displacement, shear, acceleration, maximum total and plastic deformation and energies of different parts of this system. It can be inferred from the results that desired efficiency extent of this system occurs in the range of 30–70% for the mass isolation ratio. In addition, the novel approach has prevented the full isolation of the base columns (even up to 70% reduction in isolation capacity) and by removing operational limitations such as providing a large performance gap in dense urban areas, compared to a full-isolated structure, it reduces the cost of construction.