## 6 Discussion  
As presented in the previous sections, a set of pushover analyses are carried out on the existing RC building and on the retrofitted building. In this section, a critical discussion of the results obtained is provided, also comparing the capacity curves of the unreinforced and reinforced building with the performance of the RC-framed skin only. As an example, Figure 15 shows the three curves (unreinforced building, reinforced building, RC-framed skin only) in the case of uniform pushover analysis, highlighting the effect of the proposed intervention in terms of maximum shear capacity that increases  
Figure 14: Retrofitted building, uniform pushover in Y direction. Curvature distribution corresponding to a top displacement of about: (**a**) 100 mm; (**b**) 200 mm (attainment of the LS chord rotation capacity on a column of existing building). Figure 13: Retrofitted building, uniform pushover in X direction. Curvature distribution corresponding to a top displacement of about: (**a**) 100 mm; (**b**) 180 mm (attainment of the LS chord rotation capacity on a column of existing building). respectively of about 4.5 times in X direction and more than 9 times in Y direction, i.e., the weak direction of the existing building. It is possible also to see that the reinforcing frame increases significantly the stiffness of the building both in X and Y directions with an increase respectively of about 2 times and 10 times. The last very high value in the weak direction is due to the change of structural behavior from cantilever-like for the existing building to frame-like for the reinforced building. Of course, this aspect is important if the reinforcement is designed also to reduce the displacements and consequent damages to nonstructural components in the case of moderate earthquakes. Concerning the displacement capacity, in X direction the displacement corresponding to the ultimate condition (attainment of ultimate chord rotation in columns) is increased of about 90%. Indeed, comparing Figure 13a with Figure 7b it can be observed that, for a given value of top displacement, the reinforcement reduces the curvature at the bottom sections of the existing columns of almost 50%, so avoiding the formation of the soft-story mechanism, because the deformations are better distributed along the height of the existing structure. On the other hand, in Y direction the ultimate displacement remains substantially the same if one considers the attainment of ultimate chord rotation, while it increases of about 20% if one considers the attainment of shear capacity in the flat beams of the existing building that is avoided in the retrofitted building. Moreover, it is worth noting that the maximum shear capacity of the retrofitted building in the strong direction reaches a value higher than the simple superposition of the existing building and RC-framed skin results of about 20%. This can be ascribed to the change in the mode of failure of the structure from a brittle soft-story collapse (for the existing building), to a more ductile one (for the retrofitted building), as described respectively in Section 4 (see also Figures 7 and 8) and in Section 5 (see also Figures 13 and 14). On the contrary, in the weak Y direction no difference between shear capacity of the retrofitted building and the simple sum of capacities of original structure and reinforcement is observed (Figure 15b). The different failure-mode in the X direction for the retrofitted building with respect to the original building is also confirmed by the inter-story drift (ISD) distribution along the building height. Actually, Figures 16 and 17 show the evolution of the distributions of the ISD in the case of uniform pushover analysis for the existing RC building with and without retrofit measures.