# Seismic Assessment of Historical Masonry Buildings at Different Scale Levels: A Review
## 2 Large-Scale Approaches
### Hybrid Methods  
By combining them, hybrid methods (see Table 3) try to overcome the respective limits of empirical and mechanical methods--e.g., partial or lack of proper data and computational effort--by using specific models. Numerical input/output from mechanical models meet statistical and stochastic data to define the risk-related parameters. In this way, the most suitable approach can be selected according to the available information and the building typology. Issues related to applicability and reliability probably represent the main shortcoming of hybrid methods, influenced by the definition of proper mechanical and structural features in numerical terms and by the appropriate management of the uncertainty sources related to vulnerability, exposure and hazards [60]. [PERSON], [PERSON] [47] introduced one of the first hybrid approaches (later refined in [PERSON] and [PERSON] [108], [PERSON], [PERSON] [109], [PERSON] [113]), aiming at analysing the consequences of the earthquake striking Barcelona in 1995 in terms of building vulnerability. The GNDT form [36] was adopted to generate vulnerability curves from a post-earthquake damage survey, introducing the normalisation of the vulnerability indexes ranging between 0 and 1. At the same time, the Monte Carlo method allowed the simulation of vulnerability functions related to seismic intensity that were different from those of the 1995 earthquake. Sixty different unreinforced masonry building typologies were analysed to determine the capacity curves using simplified mechanical models, stressing the importance of calibrating the numerical results through survey data. A hybrid method widely used in Greece, even if calibrated for RC buildings, has been developed by [PERSON], [PERSON] [110] to analyse an area where only a few empirical data were available. Avoiding resorting to data collected in similar regions, the authors proposed a mechanical model that was reliable in describing the building behaviour for a representative seismic load. The models were calibrated thanks to earthquake data so that DPM matrices could be obtained in a cost-benefit framework. This method was broadly used with a few variations, showing good reliability when buildings are investigated with accuracy [111; 112; 114]. In the framework of the RISK-UE project [66], two methodologies were developed for the vulnerability assessment of existing buildings and the evaluation of earthquake risk scenarios. The first accounted for a macro-seismic model defining the vulnerability through vulnerability curves and macroseismic hazard maps, while the second proposed a mechanical-based model defining the vulnerability using capacity curves and requiring the hazard in terms of peak ground acceleration [21]. As explained in [PERSON] [115], three levels were defined according to an increasing level of knowledge and a different operating scale. More recently, the procedure developed by [PERSON], [PERSON] [116] for the aggregated assessment of a building was introduced. The cluster was decomposed into its structural units, and a hybrid technique based on the CSM method was adopted by modelling the structures through the 3 Muri(r) software and performing pushover analysis. A correlation between the bilinear capacity curve and the EMS98 was then adopted to estimate fragility curves and damage probability distributions. Moreover, the indirect technique of [PERSON], [PERSON] [37] and [PERSON], [PERSON] [43] was used to allow a comparison of the results. A similar analysis of a masonry cluster was performed by [PERSON] and [PERSON] [117] to investigate the influence of the structural unit position within the aggregate on the structural capacity. Two structural units placed in intermediate and head positions were selected and analysed by means of a pushover analysis performed with 3 Muri(r) software and a quick assessment based on [PERSON], [PERSON] [37].