Seismic Response of Torsionally Coupled Building Isolated with Multiple-Variable Frequency Pendulum Isolator

Abstract

The behavior of torsionally coupled structures isolated with a Multiple-variable frequency pendulum system (MVFPI) is presented. Friction pendulum system (FPS) has limitations due to constant isolator period and restoring force characteristics, while this MVFPI overcomes this limitation. The sliding surface of MVFPI was predefined as a continuous piecewise function to combine the seismic performance of MVFPI with different seismic intensities. The governing equations of motion of the building-isolation system are derived and solved by New mark's step-by-step method assuming a linear variation of acceleration over a small-time interval. Six pairs of near-fault ground motions are selected as input ground motions in this study. The coupled lateral-torsional response is obtained under different parameter variations for selected earthquake ground motions. Moreover, some parametric study of structure isolated with MVFPI has been compared with FPS. The parametric study's numerical results help to understand the torsional behavior of the structure isolated with MVFPI. It is found that the MVFPI behaves remarkably better than FPS to reduces the base shear and base torque responses.