## 3 Description of the Case Study: An Existing RC Building
### Evaluation of the Seismic Demand and Non-Linear Dynamic Analyses
\begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Earthquake Event** & **Date** & **M [-]** & **Fault Mechanism** & **D [km]** \\ \hline EQ1—Bingol & 05/01/2003 & 6.3 & Strike-slip & 11.79 \\ \hline EQ2—Christchurch & 06/13/2011 & 6 & Reverse & 5.1 \\ \hline EQ3—Darfield & 09/03/2010 & 7.1 & Strike-slip & 13.31 \\ \hline EQ4—E Off Izu Peninsula & 05/03/1998 & 5.5 & Reverse & 9.5 \\ \hline EQ5—EMILIA\_Pianura\_Padana & 05/29/2012 & 6 & Reverse & 4.73 \\ \hline EQ6—Friuli 4 th shock & 09/15/1976 & 5.9 & Reverse & 16.83 \\ \hline EQ7—Hector Mine & 10/16/1999 & 7.1 & Strike-slip & 28.61 \\ \hline EQ8—Honshu & 08/10/1996 & 5.9 & Reverse & 13.89 \\ \hline EQ9—Hyogo-Ken Nanbu & 01/16/1995 & 6.9 & Strike-slip & 16.6 \\ \hline EQ10—Landers & 06/28/1992 & 7.3 & Strike-slip & 13.08 \\ \hline EQ11—L’Aquila mainshock & 04/06/2009 & 6.3 & Normal & 5.65 \\ \hline EQ12—Loma Prieta & 10/18/1989 & 6.9 & Oblique & 27.59 \\ \hline EQ13—Mid Niigata & 10/23/2004 & 6.6 & Reverse & 16.42 \\ \hline EQ14—Mt. Fuji Region & 03/15/2011 & 5.9 & Strike-slip & 12.8 \\ \hline EQ15—N. Miyagi Prefecture & 07/25/2003 & 6.1 & Reverse & 9.93 \\ \hline EQ16—Northridge & 01/17/1994 & 6.7 & Reverse & 20.19 \\ \hline EQ17—Off Noto Peninsula & 03/25/2007 & 6.7 & Reverse & 6.64 \\ \hline EQ18—Olfus & 05/29/2008 & 6.3 & Strike-slip & 8.25 \\ \hline EQ19—South Iceland & 06/17/2000 & 6.5 & Strike-slip & 5.25 \\ \hline EQ20—Southern Iwate & 06/13/2008 & 6.9 & Reverse & 23.08 \\ Prefecture & 10/06/2000 & 6.6 & Strike-slip & 11.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Selected ground motion records from European Strong Motion Database [37]: \(D\) denotes the epicentral distance of the event in and \(M\) the related magnitude. The force in the hysteresis loops \(f_{b}\) has been evaluated according to Equation (3). The effectiveness of the seismic isolation retrofitting can be appreciated by the comparison between the base shear \(V_{b}\) from the FB numerical model to the one of the BI numerical model (Figure 10). Note that the base shear assessment for the FB numerical model derives from the restoring forces, whereas for the BI numerical model derives from the inertia forces. The maximum values of the base shear are concentrated in the time interval in which there are the peak values of the accelerations. The dominant values of the base shear for both models are recognised in the transverse direction Y, namely \(V_{b,y}\), due to the higher stiffness of the structure. The results highlight that the retrofitting intervention may avoid brittle shear failures with reference to frames characterized by high stiffness if compared to the others. Furthermore, Figure 10a highlights a small residual plastic deformation of the column of the FB model along Y direction. The shear verifications  
Figure 8: Scaled acceleration spectra for FB (**a,b**) and BI (**c,d**) structure of the 21 real ground motion records in X direction (**a,c**); Y direction (**b,d**). Figure 9: Hysteresis loops of the FP bearing under the motion of the EO5 after scaling process. of each structural member has been performed according to [30] in order to confirm that shear failure does not occur during the non-linear dynamic analyses for the BI structure. Starting from these values, the results of the time history analyses in terms of average interstory displacements \(d_{r}\) have been determined for each floor of the structure and for both X and Y directions. By this way, the interstory drift index \(IDI\) have been calculated as:  
\[IDI=dr/h \tag{6}\]  
where \(h\) is the interstory height. In Figure 11 the _IDI_s are plotted as a function of the elevation of the building for both the FB and BI models along both X and Y directions. In transverse Y direction the _IDI_s are smaller than in longitudinal X one because of the differences of the stiffness of the frames in Y and X directions.