## 4 Conclusions  
The detection and quantification of damage to reinforced concrete (RC) buildings is an important area of research driven by the recurrent and significant damage caused by earthquakes over the years and by the possibility of creating digital twins of existing buildings to directly assess damage after earthquakes. The aim of this work was to evaluate the effectiveness and reliability of different damage indexes to ultimately identify tools that can improve seismic risk assessment and demonstrate their potential applicability for digital twins of RC buildings, which is crucial for post-earthquake assessment. First, a comprehensive literature review was conducted to examine damage indexes that have been developed and used in the past. Notable examples include the indexes proposed by Lybas and Sozen, Park and Ang, and Banon and Veneziano. Following the literature review, the study focused on evaluating the efficiency of selected damage indexes for an RC reference building. This building was analyzed under three different structural configurations: an existing gravity-only moment-resisting frame, a code-compliant moment-resisting frame, and a code-compliant shear wall system that accounts for seismic loading. In addition, both the bare frame and the masonry infilled frame conditions were analyzed for each building configuration. The seismic performance of the building was thoroughly evaluated using Multi-Stripe Analyses, which allowed for a detailed assessment across different intensity levels. The study shows which indexes are most suitable for certain situations and which are less effective. It is worth noting that cycle-related indexes were not considered as they cannot be directly compared to other indexes unless a rescaling approach is provided. This limitation results from their mathematical formulation. In particular, by summing the damage from each hysteretic cycle, the index value can exceed 1, so a direct comparison with other indexes--which are typically defined between 0 (no damage) and 1 (collapse)--is not possible. In the case of cycle-related indicators, specific performance values must be defined for each index. In BF configurations, most indexes effectively detect damage without misinterpreting the LS and CP/GC states, with the exception of the FDR-Banon index. Among these, Lybas and Sozen's index and Powell and Allahabadi's index have been found to be the optimal choice for all BF configurations, as they consistently have lower scatter values for the CP and GC limit states. For the IF configurations, the FDR-Banon index proved to be the most efficient index for the pre-coded moment-resisting frame. This index has the lowest overlap between the LS and CP/GC limit states and one of the lowest scatter values for the CP and GC limit states. In contrast, Lybas and Sozen's index is the most effective choice for both moment-resisting frames and shear wall systems in code-compliant buildings. It minimizes overlap and scatter while optimizing calculation time, making it the preferred index for these configurations. For non-structural elements, such as masonry infill, both the Lybas and Sozen index and the Powell and Allahabadi index proved to be the most efficient options for assessing the extent of damage. In addition, a new dissipated energy-based index was developed based on the ratio between the area under the trilinear curve of the infill panel up to the point reached during the analysis and the total area under the curve. The results show that all three indexes can capture the growth and increase in infill panel damage in all building configurations studied, making them effective tools for detecting damage to closure panels regardless of building typology. In particular, the Powell and Allahabadi index and the energy-based index are especially effective for the progressive assessment of damage to these elements, while the Lybas and Sozen index can lead to an underestimation of damage.