Seismic Rehabilitation of 10-Story Steel Building by Adding an Isolated Story at Roof Level

The application of seismic isolators at the base or mid stories by employing the mechanism of tuned mass dampers (TMDs) in structures provides an effective seismic control method for buildings. In this study, three prototypes of 10-story steel moment-resisting frame structures with intermediate ductility that are designed in accordance with second and fourth editions of Iranian Seismic Design Code (Standard No. 2800) as well as the second edition with one story on seismic isolator at the last floor were designed and modelled using nonlinear static pushover and nonlinear dynamic time history analyses under three far-fault earth‎quakes. The results were presented in the form of pushover curves and time history of roof displacement, base shear, maximum drift and roof acceleration of stories to compare the seismic enhancement of roof-level isolating technique and the effectiveness of the seismic criteria of Standard No. 2800. The results of research indicated that adding on isolated story at roof level had a significant effect on decreasing the drift of the stories. This reduction for the designed structure based on the second edition of Standard No. 2800 is down to an average maximum of 25%. In addition, using seismic isolators reduces the base shear by 30%. The decrease in the amount of roof displacement is also 40%. Also, the results showed that the efficiency of isolated story application as the last story to reduce the damage.