Abstract

This research aims to evaluate the effect of the dynamic parameters of the isolation system (the degree of torsional coupling (Ω_b), the period of vibration (T_b), the critical damping ratio (ξ_b), and the stiffness eccentricity of the isolation base (e_rb)) on the torsional behavior of a six-story reinforced concrete building family, considering the stiffness or mass eccentricities (er or em, respectively) in the superstructure. These modify structural behavior under severe earthquakes and increase lateral displacements and drifts. For this purpose, a nonlinear time-history analysis was performed on each model by subjecting them to a set of seven seismic accelerations records, measured on the coast of Peru and Chile, which were scaled following the pseudo-acceleration design spectrum from Peru.

The main global responses were the maximum lateral displacements and the inter-story drifts. It was observed that the effect of em generated more amplification on lateral displacements and drifts than er. In a similar way, the parameter erb was very influential on the torsional behavior of the isolated buildings with e_m and e_r, amplifying lateral displacements up to 50 %. In addition, the parameter T_b impacted mostly on the inter-story drifts, reducing it up to 55 %. On the other hand, the parameters Ω_b and ξ_b did not significantly influence the responses of interest.

Keywords Elastomeric; irregularity plan; isolated building; mass eccentricity; parametric study; stiffness eccentricity