Seismic performance evaluation of base-isolated buildings with variations of mass and stiffness

Significant investigations have been undertaken regarding base-isolated structures. However, various factors, such as substantial renovations in base-isolated buildings, the installation of heavy machinery in base-isolated hospitals, or the degradation of isolator stiffness, can lead to changes in a building's mass and stiffness over time. These alterations, often overlooked in existing literature, can affect the structure's natural period, resulting in seismic accelerations and bearing displacements that may exceed anticipated limits. This issue has not been thoroughly explored in the base isolation literature. Consequently, this study examines a nine-story isolated building whose seismic performance has been experimentally validated. The building is modelled using MATLAB platform, which is also verified by experimental findings. The results indicate that variations in mass and stiffness in base-isolated buildings can result in increased isolator bearing displacement and overall frame acceleration. Consequently, this concern highlights the need for additional vibration control measures for base-isolated buildings to prevent excessive acceleration and bearing damage.