Eva Coisson

The Crack Pattern in Brunelleschi's Dome in Florence: Damage Evolution from Historical to Modern Monitoring System Analysis

The aim of this paper is to show the potentiality of the historical analysis mixed with the experimental data elaboration in identifying the mechanical behavior of an ancient monument. Firstly, an ideal route through the crack pattern of Santa Maria del Fiore dome in Florence is presented herein: the conclusion of the historical debates about the mechanical behavior of the dome are analyzed in light of the statistical interpretation of the last 55years cracks monitoring data. The recall of some historical debates has been fundamental in the comprehension of its mechanical behavior, showing the validity of the empiric-experimental method in ancient master builders solution (the “art of building” rules) to the main problem of the masonry domes: their primeval and ineradicable horizontal thrust on supporting structures. The final aim is to present some results on the beneficent effect of the scaffolding installed on the dome from 1980 to 1996, which seems to confirm the prevision made by Vincenzo Viviani at the end of XVII century on the future consolidation of this dome.

Analysis of damage mechanisms suffered by Italian fortified buildings hit by earthquakes in the last 40 years

This paper presents an empirical approach to studying the seismic behaviour of fortified buildings, including castles, fortresses, and citadels. The first step for a focused preventive intervention on this building typology, characterised by the presence of towers, defensive walls and other particular elements, is to identify recurring vulnerabilities. Over 750 castles and 7 seismic events which have hit Italy in recent decades have been considered, including the earthquakes in Central Italy in August and October 2016. For each seismic event, the characteristics of the earthquake have been described by means of shake maps, while the castles in the area have been identified and inserted in a specifically formulated geographic information system. Subsequently, a thorough archival and bibliographical research on the damage suffered by the most significant case histories allowed the comparison of the damage observed in the castles with different characteristics in terms of soil, materials, building typologies and conservation status. A previously proposed table of damage mechanisms was adopted and verified on a larger number of castles, suggesting some modifications. Lastly, statistical analysis on these data was conducted in order to inspect possible connections between building features, peak ground acceleration and damage mechanisms. The results have shown a good agreement with the existing vulnerability curve and the small amount of numerical analyses proposed in the literature for the same building typology.

A New Numerical Approach to the Structural Analysis of Masonry Vaults

The present paper concentrates on the numerical modelling of masonry vaults, adopting a type of analysis first developed at the University of Parma for applied mechanics, based on the use of non-smooth dynamics software, through a Differential Variational Inequalities (DVI) formulation specifically developed for the 3D discrete elements method. It allows to follow large displacements and the opening and closure of cracks in dynamic field, typical of the masonry vaulted structures. Once the modelling instrument was calibrated, thanks to the comparison with the recurrent damage mechanisms previously analysed, it was also applied to foresee the behavior of the same structure with different actions and with different types of strengthening. The development of damage mechanisms, both in quasi-static cases (for insufficient lateral confinement or for possible soil settlements) and in the occurrence of seismic events, make this type of structures very difficult to be modelled precisely with other methods. Given the three-dimensional CAD model of a vault modeled with a great number of masonry units with specific positions and pattern, the method proved to be able to reproduce the behavior of the structure under both static and seismic loads, showing the mechanism of collapse, the network of contact forces, the displacements and other useful data. The aim is to inspect the possible influences in the structural behavior given by the discrete geometry and the changes in the mechanisms development given by different strengthening interventions. Once the modeling instrument will be calibrated, also through the comparison with real cases and with the results obtained through limit analysis, it will be possible to adopt it as a base also for the prevision of the future behavior of the vaults subjected to strengthening, avoiding uncalibrated and uncritical applications of materials based more on trends rather than on a thorough analysis for the specific case.

Monitoring the French Panthéon: From Rondelet’s Historical Surveys to the Modern Automatic System

The damage of a historical structure can be today controlled with many sophisticated instruments. Nevertheless, this type of monitoring can give information only over a very short period of time compared with the long life of the building. This approach can be insufficient to reconstruct the whole evolution of the damage, and thus to understand the stress distribution inside the structural elements, particularly in cases for which long-term phenomena (such as viscosity or soil settlements) are present. To reach this more complex aim, an approach of historical monitoring should be applied, both looking at technical historical documents and surveying the traces of history directly on the monument itself. The case of the French Panthéon is presented in this study, showing the usefulness of this approach also for the present stability assessment. The comparison among the plentiful historical documentation (including 18th-century surveys, monitoring, and technical reports), the present surveys of deformations and the “modern” structural monitoring allowed a complete quantitative reconstruction of the main damages evolution from the construction till now, laying the base for a possible future conscious intervention.

Structural Monitoring of Historical Constructions: Increasing Knowledge to Minimize Interventions

In all the fields of restoration, from the artistic to the architectural one, the principle of minimum intervention is always mandatory: no work is allowed if not effectively needed for the perpetuation of the cultural heritage to the future generations. Within the architectural restoration interventions, this approach should be applied also to the structural ones, but often this doesn’t happen, in part for safety’s sake, in part for the cultural unpreparedness of some technical designers, who work indistinctively on new and old buildings. Increasing the knowledge and the understanding of the ancient monuments structural behaviour is the only method to decrease the uncertainties and in consequence to minimize the interventions, whose effective necessity has to be proven, in line with the theoretical requests. In step with this, the structural monitoring, with its different approaches, represents an important mean to increase this knowledge, investigating what happened to the structure in the past, understanding its present evolution and also controlling it in the future. The aim of this paper is therefore to inspect the role of structural monitoring in the knowledge and also in the conservation process of the built historical heritage, bearing in mind that knowledge and conservation should always go hand in hand.

The Use of Composites in Architectural Restoration: Some Critical Considerations on the Theoretical Implications

The use of composites in the field of architectural restoration is becoming more and more widespread, because of the great technical advantages they convey in many cases. But applying these materials to the Cultural Heritage poses not only technical issues, common to all the applications on the same materials, but also artistic, historical and, more generally, cultural ones. The present paper faces these issues, starting with some considerations on how they were dealt with in history, when the “new” materials were iron, steel and reinforced concrete. Then, the specific problems posed by the composite materials are discussed and some examples are shown in order to identify the correct approach to the many different cases that can arouse in the field of architectural restoration. There isn’t a single right solution for each problem, but there is a right approach that starts from the comprehension of the building’s behavior, passes through a comparison of all the possible solutions and aims at finding the best equilibrium among the technical and theoretical issues for the single case study.