12 th International Conference on Structural Analysis of Historical Constructions SAHC 2020 P. Roca, L. Pelà and C. Molins (Eds.) RECONSTRUCTED OVERHANGING BATTLEMENTS. EXECUTIVE TECHNIQUES AND THEIR VULNERABILITY IN THE STRONGHOLD OF ARQUATA DEL TRONTO (ITALY) EMANUELE FACCHI 1 , ALBERTO GRIMOLDI 1 , ANGELO G. LANDI 1* AND EMANUELE ZAMPERINI 1 1 Dipartimento di Architettura e Studi Urbani (DAStU), Politecnico di Milano piazza Leonardo da Vinci 26, 20133 Milano, Italy e-mail: angelogiuseppe.landi@polimi.it, www.polimi.it (*corresponding author) Keywords: Fortified Buildings, Overhanging Battlements, Seismic Vulnerability Abstract. The stronghold of Arquata del Tronto was heavily damaged by earthquakes in 2016 and it drew the attention of the experts in reinforcing historic buildings. They regarded it as a case study, a predicting model of the failure in employing specific construction elements in fortified architecture, whose geometric and material data were only approximately considered. The overhanging battlement is the most seriously damaged part of the building and has raised particular attention and interest. As often happens in other castles and fortresses, it dates back to the late 19 th and even more to the 20 th century. A first close examination of the building’s repairs shows how the new additions, whose maintenance is difficult, ended in failure. The additions were inspired by ancient details, but nonetheless they are unreasonable from the point of view of structure and durability: they – and even more the irrational repairs of the last decades – are the principal cause of failure. Material decay – closely linked to circumstances and places – has also played a decisive role. An extensive and rigorous historical research is necessary to find the sources and to evaluate their nature and limits, as well as to relate all information to the building, thus operating in close correlation with the building archaeology, by now a so widespread and consolidated research field. . Jointly, the written documents and the building itself in its historical stratification allow a better analysis of the structural behaviour , an essential step to achieve an effective restoration planning. 1 THE XIX CENTURY STUDIES ON MEDIEVAL FORTIFICATIONS AND THEIR RECENT USE IN THE FIELD OF STRUCTURAL STRENGTHENING Recent technical literature on seismic prevention aimed at developing calculation models and identifying typical cases in order to take preventive action. For this purpose, the studies outline a story in broad lines, by types and periods (which only conjure the infinite number of possible variants), and in parallel develop a synthetic calculation of some concrete cases, only in broad terms corresponding to the identified types. By quantitative data, this kind of approach reiterates only some intuitive general remarks. Actually the heterogeneity of construction techniques and decay, peculiar to each building, as well as the numerous repairs carried out in areas of high seismic risk – where damage has repeatedly occurred – determine very different behaviours. So the results could be scarcely useful in few actual cases, whose