# A Review of the Performance of Infilled RC Structures in Recent Earthquakes
## 4 Case Study
### Assessment of Possible Strengthening Interventions
The second strengthening scenario included two RC shear walls on the longitudinal direction and two in the transversal direction with a thickness of 25 cm and located and full filling the left and right bays of the building in each direction. The thickness and the reinforcement were designed according to Eurocode 2 [53] and Eurocode 8 [54]. The third strengthening proposal was applying two diagonals ('X' configuration) of steel braces (SB) HEA 240 and two diagonals of HEB 220 in the longitudinal and transversal direction respectively, in the same bays as where the RC shear walls were applied in solution 2. Finally, the fourth strengthening proposal consisted of applying steel braces with energy-dissipation device associated (Solution 4), which can increase stiffness and the damping of the building and consequently reduce the deformation demands. This strengthening technique was based on the solution proposed by [PERSON] [13]. The model was implemented on the computer program and was calibrated with experimental results of a full-scale cyclic test of a retrofitted frame with the same dissipative device [13]. The hysteretic behaviour and the energy dissipation resulting from the calibration analysis are presented in Figure 29a,b, respectively. The non-linear dynamic analysis presented in Figure 30 computed the maximum inter-storey drift ratio, the ratio between the maximum inter-storey drift reached by the  
Figure 29: Strengthening solution 4: (**a**) energy dissipation and (**b**) hysteretic behaviour results from the calibration analysis. strengthening model and the as-built model and the cumulative energy dissipation reached by the strengthening model and the as-built one. Starting from the analysis of the maximum inter-storey drift ratio (Figure 30a,b), all the strengthening solutions were quite efficient to reduce the maximum drifts below the drift limits. The most efficient one on reducing the maximum drift was solution 3 in both building directions and the lowest efficient was solution 1 in the transverse direction. In the longitudinal direction, solution 2 was the most efficient until 0.27 g, and for PGA larger than 0.27 g it was solution 3. The ratio between the maximum drift reached by the strengthening models and the as-built one is presented in Figure 30c,d. From that, it can be noticed that the strengthening solutions had a higher impact on the transverse direction since the ratio varied between 0.1-0.35. In the longitudinal direction, the ratio ranged between 0.15 and 0.45. Finally, it is important to draw a final analysis of the strengthening efficiency in terms of cumulative energy dissipation (Figure 30e,f). It is possible to verify that the strengthening provided higher energy-dissipation capacity in the longitudinal direction, increasing between 1.1 and 3.5 times. The strengthening solution that provided more energy dissipation was the strengthening solution 2 until 0.14 g and strengthening solution 3 for PGA larger than 0.14 g. The strengthening solution 4 was the one that dissipated lower energy. Figure 30: Analysis of the efficiency of the strengthening solutions: **(a)** maximum inter-storey drift ratio (longitudinal direction); **(b)** maximum inter-storey drift ratio (transverse direction); **(c)** ratio between the maximum inter-storey drift (strengthening/as-built) in the longitudinal direction and **(d)** transverse direction; **(e)** ratio between the cumulative energy dissipation (strengthening/as-built) in the longitudinal direction and **(f)** transverse direction. Regarding the transverse direction, strengthening solution 2 was again the strategy that dissipates more energy and solution 3 the lowest one. It should be mentioned that the strengthening solutions increased the energy-dissipation capacity up to 50%.