EFFECTS OF EXCITATION CHARACTERISTICS ON THE EQUIVALENT LINEAR SYSTEM OF A BUILDING STRUCTURE WITH MR DAMPERS

摘要

Seismic control performance of MR dampers, which have severe nonlinearity, changes with respect to the dynamic characteristics of earthquake excitations such as magnitude and frequency contents. In this study, effects of excitation characteristics on the equivalent linear system represented by an equivalent damping ratio for single-degree-of-freedom (SDOF) systems with a MR damper are investigated through extensive numerical analysis for various natural frequencies of the structures and design parameters of the MR damper. In addition, to implement an equivalent linearization procedure considering non-stationarity and frequency contents of the earthquake excitation, seismic response reduction factors for artificial earthquake ground motions are proposed using regression analysis of linear structural responses obtained from numerical analysis. Equivalent linearization results show that the relative magnitude of the excitation compared with the friction force of the MR damper and the frequency contents of the excitation affect the equivalent damping ratio considerably, and appropriate combination of the friction and the viscous damping produces additional damping effect.