## 9 Conclusions  
This paper presents a refined design procedure for the seismic retrofitting of single-storey RC frames, e.g., warehouses, logistic centers, and sports halls, by means of hysteretic braces. In particular, with respect to the provisions of \"Method-B\" of the Italian Building Code, two novelties are introduced:  
1. Definition of two performance targets to tailor retrofitting interventions to the protection and/or damage limitation of the \"drift-sensitive\" masonry infills and glazed curtain walls that typically bound these buildings. These targets are expressed in terms of inter-storey displacement thresholds that are calibrated depending on their geometric and mechanical parameters. 2. Adoption of a more recent and accurate formulation for estimating the equivalent viscous damping developed both by the main RC frame and the dissipative braces during seismic shaking. The suitability of this design framework, called \"Method-B1\", has been proven through application to a case study building, namely, a sports hall located in Northern Italy built in the early 1970s and affected by important structural deficiencies. First, propaedeutic interventions were proposed, see Section 4. Afterwards, the six steps of \"Method-B1\" were carried out by means of iterative displacement response spectrum analyses in order to identify the dampers' layout that fulfill the two performance targets. In the longitudinal (X) direction, the upper windowed band interrupting the integrity of the masonry infills causes a sharp decrease in the frame lateral stiffness. Although the building features only one storey, optimized dampers capable of compensating for this irregularity were arranged on two levels: the first level (L1) below the windows, and the second level (L2) horizontally aligned with the same. Based on the mechanical and geometric properties of both masonry infills and glazed windows, it was possible to identify two inter-storey displacement thresholds: (1) for level L1, \(d_{PP,L1}=14.0 mm\); and (2) for level L2, \(d_{PP,L2}=13.0 mm\). At roof level, the lateral target displacement was set to \(d_{PP}=d_{PP,L1}+d_{PP,L2}=27.0 mm\). On the contrary, in the transversal (Y) direction, thanks to the absence of any significant discontinuity in the masonry infills, the hysteretic dampers were installed on a single level; note that in this case L1 spans from the foundations to the roof. Having identified the optimal damper layout (i.e., the number of devices, their yield strength, and a ductility level that allows the attainment of both design targets), the effectiveness of the proposed solution was proven through comparison with the results of NLTH analyses. The following outcomes can be concluded:  
* In the longitudinal (X) direction, two design iterations were performed. The first set of design parameters used for the dampers, despite ensuring the integrity of the two \"drift-sensitive\" components, resulted in a maximum roof displacement significantly lower (\(-31\%\)) than the target value. In the second iteration, the dampers' effective stiffness and yielding strength at level L1 were decreased to compensate for the higher rigidity of the bottom masonry infills. Although slightly affecting the integrity of the same, this allowed us to get closer to the displacement target (\(d_{max,L1}=12.5 mm\) vs. \(d_{PP,L1}=14.0 mm\)). At level L2, the dampers' parameters were fixed in the first iteration, as the calculated response was coincident with the target (\(d_{max,L2}=12.6 mm\cong d_{PP,L2}=13.0 mm\)). The resulting overall lateral displacement at roof level was equal to \(d_{max,L1}+d_{max,L2}=25.1 mm\) (i.e., \(-7.0\%\) respect to \(d_{PP}=27.0 mm\)). * In the transversal (\(\Upsilon\)) direction, the optimal damper parameters were identified in the first iteration, as despite the single layer of dampers both performance targets were met (\(d_{max,L1}=12.9 mm\) and \(d_{max,L2}=12.4 mm\) were close enough to the relevant targets, i.e., \(d_{PP,L1}=14.0 mm\) and \(d_{PP,L2}=13.0 mm\), respectively).