## 2 Research Methodology  
The adopted research methodology is based on the uncertainty estimation approach recently proposed by [PERSON] et al. [16], who further integrated the estimation of modeling uncertainty in existing buildings, using a case-study masonry-infilled RC frame from an extensive building stock [17], representative of existing RC frames built in Italy between 1970 and 1980. The approach adopted by [PERSON] et al. [16] covers some important aspects that were unaddressed by previous research studies on this topic, namely:  
1. The variability around the mechanical properties of masonry infills was considered. Five masonry infill typologies, from weak to strong, classified according to their shear strength, were selected as representative of the masonry infill typologies used in RC buildings in Italy [18];
2. The single strut macro-modeling technique generally implemented in previous studies was replaced by the three-strut modeling approach proposed by [PERSON] et al. [19]; this modeling approach enabled a better estimation of the local interaction between frame and infills and, consequently, a more trustworthy estimation of the shear and moment distribution in the surrounding RC frame, as also pointed out by [PERSON] et al. [14,15];
3. Adoption of a numerical model for RC members able to account for material and geometrical nonlinearity, flexible joints with likely shear failure, the behavior of poorly detailed and non-ductile RC frame members, premature shear failure, deficiencies in concrete core confinement due to stirrups spacing, and inelasticity concentrated in the structural element ends;
4. The shear response parameters of RC members, such as beams and columns, were treated as a source of uncertainty, highlighting the relevant impact of the shear failure of poorly detailed RC members in the seismic performance assessment of GLD buildings. In line with the above, this study makes use of the improved epistemic uncertainty estimates provided by [PERSON] et al. [16] to quantify the impact of modeling uncertainty on the loss assessment of an existing masonry-infilled RC school building in Italy, analyzed fully through a 3D numerical advanced model[PERSON] The points briefly discussed below summarise the adopted research methodology (Figure 1):  
1. A representative case-study school building was selected as representative of the RC school buildings in Italy, according to the main features characterizing the existing school building stock [6];
2. The macro-level classification of masonry infills outlined in [PERSON] et al. [18] was used to account for the variability of the geometrical and mechanical properties of the masonry infills[PERSON] This also allows us to investigate the impact of different masonry infill typologies on the capacity curves and on nonlinear time history response analysis, leading to the economic loss estimation related to different non-structural components;
3. On the structural model side, the choice of explicitly modeling the presence of openings was investigated to analyze its role in the estimation of fragility curves, considering two structural configurations: (i) completely infilled structural configuration, disregarding the presence of the openings, and (ii) partially infilled structural configuration, considering the presence of the openings, whose dimensions were set according to the original drawings of the school building;4. The impact of a more comprehensive modeling uncertainty characterization on the loss assessment of the selected case-study school building was investigated by means of two sets of dispersion values: the first set includes the values proposed by [PERSON] and Sullivan [11], whereas the second one accounts for the values recently proposed by [PERSON] et al. [16], to gauge the differences. The seismic loss estimates were then obtained, for both structural configurations, according to the FEMA P-58-2 [3] methodology.