## 5 Discussion of the Results
### Global and Local Response from NLTHAs  
The NLTHAs allow the evaluation of the structural response of each considered frame in global and local terms. In this regard, Table 4 reports the averages and coefficients of variation (CV) of maximum inter-storey drift ratios (MIDRs) and residual inter-storey drift ratios (RISDRs), referred to the benchmark of the TF. It can be observed that the innovative frames exhibit similar MIDRs as TF with the exception of IF-TB, in which the presence of a re-centering system with lower value of yielding moment leads to an average increase in the MIDR on both the first and the second floors. Moreover, it is noteworthy to highlight that, in the absence of re-centering systems (i.e., in IF), the RIDR is more than two and four times than the TF at first and second level, respectively. Conversely, analyzing the results provided by IF-TB and IF-FD in terms of RIDR, it can be stated that the combined use of friction dampers at BCCs and self-centering systems allows for significantly limiting the RIDR. However, it should be also observed that in IF-TB and IF-FD an increment of the RIDR occurs at the second level. Among all proposed solutions, the best condition is definitely achieved when the friction dampers are adopted in both BCCs and CBCs, i.e., in IF-FD; this frame provides the lowest average MIDR and RIDRs comparable to those attained in the TF.  
The NTHAs also allowed the assessment of the effective damage mitigation that can be achieved if friction devices and self-centering systems are introduced in the design of a RC MRF. Figure 10 reports the moment-rotation curves of the IF vs. TF in the beam end section (Figure 10a), at the column base (Figure 10b), in the panel zone (Figure 10c), and in the friction device (Figure 10d). From Figure 10a, it can be observed that the TF experiences plastic strains caused by the yielding of the lower rebars, while in the IF the beam behaves by following an elastic moment-rotation curve. From Figure 10b, it is observed that the adoption of friction dampers only at BCCs does not prevent the IF to the formation of plastic hinges at the column base section. As regards the panel zone (Figure 10c), it can be observed how the adoption of the BCC in the IF prevent the joint from loss of strength and stiffness that are significant in the TF instead. Therefore, in the IF, the damage of the panel zone is negligible, with limited development of cracks.  
Finally, Figure 11 reports the dissipated energy at the column base section (Figure 11a) and in the re-centering devices (Figure 11b) in IF-TB as well as IF-FD. It can be observed that, in both frames, the column base section behaves elastically. However, looking at Figure 11b, it has to be noted that the connection in the IF-TB attains a lower maximum moment and a higher rotation, but the minor value of bending moment conducts to a feebler frame with high values of MIDRs. Moreover, the friction self-centering system in IF-FD dissipates a significant energy amount thanks to its moment-rotation diagram characterized by a flag-shape.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**MIDR**} & \multicolumn{4}{c}{**RIDR**} \\ \hline  & & **TF (\%)** & **IF/TF** & **IF-TB/TF** & **IF-FD/TF** & **TF (\%)** & **IF/TF** & **IF-TB/TF** & **IF-FD/TF** \\ \hline First & avg. & 2.72 & 0.94 & 1.17 & 0.94 & 0.17 & 2.76 & 0.59 & 0.53 \\ storey & CV (\%) & 13.27 & 18.14 & 12.61 & 13.86 & 77.99 & 79.74 & 86.60 & 70.89 \\ \hline Second & avg. & 2.91 & 0.98 & 1.07 & 0.91 & 0.14 & 4.21 & 1.71 & 1.36 \\ storey & CV (\%) & 11.16 & 16.58 & 17.04 & 17.91 & 78.71 & 78.15 & 79.57 & 76.96 \\ \hline \hline \end{tabular}
\end{table}
Table 4: MIDR and RIDR of MRFs with friction dampers vs. TF.