Abstract:The research on the existing isolated structure mainly focuses more on the isolation bearing, but less on the influence of the mechanical properties on the seismic performance of the whole isolated building. In this paper, the seismically isolated RC frame structures are designed to the Chinese seismic code and the column size is increased in turn to study its influence on the seismic performance of the isolated structures. In this paper, SAP2000 is adopted to conduct pushover analysis of four isolated structures using inverted triangle loading mode and uniform distributed loading mode, and the capability spectrum method is employed to evaluate the seismic performance of the isolated structures. The analysis results show that the shear demands of the isolated structures are smaller than the corresponding common structures when the same roof displacement is achieved, so their seismic performance is superior to the common structures. By analyzing the plastic hinge development and comparing the inter-story drifts for different models, as the column size is increased, the damage to the isolated structures is reduced, and the seismic performance of the isolated structures, especially at the first story of the structure, is improved accordingly. As the column size is increased substantially, the reduction of the inter-story drift is not significant.. Therefore, an increase of 10% in the column size over 600mm is the most effective measure to improve the seismic performance of the isolated structures.