# A Review of the Performance of Infilled RC Structures in Recent Earthquakes
## 4 Case Study
### Seismic Vulnerability Assessment  
The building understudy was subjected to several non-linear dynamic analyses, particularly to one artificial earthquake generated for a medium/high-risk scenario in southern Europe [48] for different return periods (Table 2). Hazard-consistent time series of acceleration (with 15 s of duration) were artificially generated, yielding a set of ten uniform hazard response spectra for increasing return periods (RP). Figure 27 shows the ground motion acceleration of seismic action for the return period of 2000 years.  
The obtained results verify the safety according to the hazard levels proposed by the international recommendations VISION-2000 [49] and FEMA-356 [50] to evaluate the building safety. In addition, other global drift limits have been used, namely the Gobarah proposal [51] recommended for non-ductile structures, which is the case of rehabilitation/strengthening of existing buildings. All the proposed limits drifts are presented in Table 3.  
The maximum inter-storey drift ratio obtained in the non-linear dynamic analysis results is plotted in Figure 28. It can be noticed that the maximum inter-storey drift reached by the building exceeds the drift limits recommended by VISION 2000 [49] and by FEMA-356 [50]. The maximum inter-storey drifts were always reached at the first level of the structure due to the absence of the masonry infill walls. Concerning the longitudinal direction (Figure 28a), the drifts are always more significant than the limits imposed by  
\begin{table}
\begin{tabular}{c c} \hline \hline
**RP (Years)** & **PGA (m/s2)** \\ \hline
73 & 0.889 (0.09g) \\ \hline
100 & 1.060 (0.11g) \\ \hline
170 & 1.402 (0.14g) \\ \hline
300 & 1.796 (0.18g) \\ \hline
475 & 2.180 (0.22g) \\ \hline
700 & 2.543 (0.26g) \\ \hline
975 & 2.884 (0.29g) \\ \hline
1370 & 3.265 (0.33g) \\ \hline
2000 & 3.728 (0.38g) \\ \hline
3000 & 4.273 (0.44g) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Peak ground acceleration and corresponding return period (RP).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Performance Level** & **VISION 2000 [49]** & **FEMA-356 [50]** \\ \hline Moderate damage (life safety) & 0.5\% & 1\% \\ \hline Extensive damage (life safety) & 1.5\% & 1–2\% \\ \hline Near Collapse & 2.5\% & 4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Performance levels and corresponding maximum limit drifts.  
Figure 27: Ground motion acceleraogram (time history for the return period of 2000 years—0.38 g).  
VISION 2000 [49], namely about +10% at 0.08 g, +45% at 0.21 g, +37% at 0.28 g, +74% at 0.32 g and +131% at 0.37 g. Moreover, the structure exceeds the FEMA-356 [50] drift limits for a PGA equal to 0.21 g (+9%), 0.32 g (+8%) and 0.36 g (+44%).  
Concerning the transverse direction, the drift limits reached during the analyses were slightly lower than those achieved in the transverse direction (22-39%), except for the PGA of 0.18 g where they get a similar inter-storey drift ratio of 1.26%. The FEMA-356 [50] drift limits were not respected since, for the PGA of 0.37 g, the structure exceeded the limit by about 5%.  
On the other hand, the VISION 2000 [49] drift limits were always exceeded, except for the PGA of 0.08 g. Based on these results, it can be concluded that this structure seems to be vulnerable under seismic action. In particular, this vulnerability is caused by the vertical irregularity caused by the masonry infill walls distribution, a problem identified in all the post-earthquake damage survey reconnaissance missions presented in Section 2.