# Seismic Assessment of Historical Masonry Buildings at Different Scale Levels: A Review
## 4 Conclusions  
The historical (unreinforced) masonry buildings represent a fundamental component of our cultural heritage, and their vulnerability towards horizontal seismic actions is nowadays a well-known issue. Despite research carried out over the past decades and an incessant development of engineering and IT practices, the analysis of historical masonry buildings still remains a challenging activity due to their intrinsic features. Limited knowledge of geometry, structural and material features, construction systems, etc., makes their analysis different (and more complex) compared to ordinary buildings. In this paper, a wide review of the most common methods for the analysis of historical masonry buildings has been presented. The advantages and disadvantages of each of them have been outlined, as well as their feasibility depending on the extent of the analysis to be carried out, the level of accuracy and the typology of data collected. A first wide subdivision of the existing methods is based on the number of buildings to be investigated. Large-scale approaches are needed when the contemporary analysis of a consistent number of buildings is required. Generally operating at a territorial scale, their aim is not a detailed structural analysis of each building but rather the identification of the most vulnerable units within a set or the prediction of the possible damage depending on the seismic input. Such methods usually need fairly basic input data, allowing a relatively prompt assessment. Among large-scale methods, empirical ones are based on the statistical elaboration of qualitative information coming from post-earthquake damage surveys, needing to be calibrated for the building typologies of a specific region. Analytical methods based on mechanical and geometrical input parameters show better accuracy in terms of results, generally at the expense of a greater computational burden and execution time. Their outcomes can be directly useful for retrofitting projects, being otherwise able to analyse a more reduced number of buildings compared to empirical methods. Aiming to overcome the respective limits of the two families of approaches mentioned, the hybrid methods were developed by combining numerical input/output from mechanical models with statistical data. As a shortcoming, their applicability is usually strongly related to the calibration performed through survey data and therefore related to a specific area. By reducing the scale of interest and focusing on a single building or on a reduced number of them, methods belonging to the small-scale approach should be adopted. Within them, limit analysis methods can be used to evaluate the failure load related to different collapse mechanisms of structures ideally subdivided into blocks. Particularly appealing for buildings, such as the historical ones, where the lack of rigid floors prevents a box behaviour, they need reduced computational requirements. On the other hand, they do not account for brittle failure modes and investigate fewer possible mechanisms compared with those detectable through plastic hinges. From this perspective, FE methods maybe represent the currently most accurate approach from the model and analysis point of view,allowing the simulation of a multitude of different situations thanks to the several options in terms of representation of geometry, simulation of materials, modelling of components and so on. As a counterpart, the more the analysed building is complex and heterogeneous, as it can be for historical buildings, the more the computational burden is relevant. To limit the complexity of the analysis, several methods have been developed to reduce a masonry structure to a simplified set of panel-scale elements simulating the building's components, typically piers and spandrels. A significant decrease in the computational effort is achieved, otherwise needing an a priori building disaggregation.