## 4 Results
For the ground floor, in the x-x direction, eight groups of superimposed steel blades with four blades with thicknesses of 7.5 mm constitute the CAR1 damper in both directions. For the first floor, in the x-x direction, it is selected a damper with five groups of superimposed steel blades with fives blades with thicknesses of 6 mm, and in the y-y direction, it is selected a CAR1 damper with five groups of superimposed steel blades with three steel blades with thicknesses of 8 mm and two brass blades with thicknesses of 3 mm. The restraining bolt needs be activated before the horizontal displacement of 3.3 cm and 2.3 cm (at the top of the building), which is equal to 3.8 cm of displacement parallel to the axes of the damper for the ground floor and 2.7 cm for the first floor in both directions. Figure 11 compares the pushover curves of all buildings (BM0, RD1 with CAR1 and RD2 with CAR1) in the x-x direction and in the y-y direction. It is noticed that the RD1 building is able to take a 149.2% (6080 kN) and 135.6% (5960 kN) higher base shear load in the x-x and y-y directions, respectively, and the RD2 building is able to take a 212.3% (7620 kN) and 198.8% (7560 kN) larger base shear load in the x-x and y-y directions, respectively, for the same level of displacement (drift = 2%). Figure 10: Plastic hinges of RD1 without the installation of CAR1 dampers for a displacement level of 18.4 cm, and axial load–displacement curves for the steel diagonal braces. Figure 12 presents the plastic hinges of RD1 and RD2 for a horizontal displacement at the top of the building of 18.4 cm in both directions. The hinges of the columns remain in the Life Safety (LS) performance level in both buildings and in both directions, so the buildings have not suffered substantial damage as a result of this horizontal displacement (Figure 12a-d). In addition, with the installation of the CAR1 dampers the buckling of the steel diagonal braces was prevented (Figure 13). Figure 11: Pushover curves of all buildings: (**a**) x-x direction; (**b**) y-y direction. Figure 13a shows the axial load-displacement curves for the steel diagonal braces of RD1 in the x-x direction of the ground floor, and Figure 13b shows those of the first floor. The activation of the restraining bolt increases the axial load of the tensional di-agonal brace, so the compressed diagonal brace is protected against buckling. A preliminary estimation of the overall inadequacy of existing RC buildings and a proper choice of effective retrofitting strategies are fundamental phases for seismic  
Figure 12: Plastic hinges of redesign buildings for a displacement level of 18.4 cm (at the top) (**a**) RD1 in x-x direction; (**b**) RD1 in y-y direction, (**c**) RD2 in x-x direction; (**d**) RD2 in y-y direction. Figure 13: Axial load–displacement curves for the steel diagonal braces of RD1 in x-x direction: (**a**) ground floor and (**b**) first floor. protection of RC buildings [32]. In this study, the effectiveness of the friction-yielding damper CAR1 has been successfully investigated for an existing low-rise (2-story) RC building that no longer meets the requirements of current anti-seismic regulations. For medium-rise and high-rise buildings (existing that no longer meet the requirements of current anti-seismic regulations), the use of the dampers CAR1 needs to further investigate additionally with other techniques like FRP that would restore or improve the column original design strength for possible axial, shear, or flexure and in some cases allow the structure to carry more load than it was designed for.