Structural assessment of the 16th century coastal watchtowers in the defense system of the Pontifical state

Abstract

Since medieval times the Mediterranean area and in particular its coasts have witnessed a series of clashes for economic and cultural domination, partially concluded, with the Battle of Lepanto in 1571. The resulting state of uncertainty and endless terror among the population pushed military engineers to develop organized coastal defense systems consisting of a network of strongholds such as watchtowers, castles and fortresses whose structural and functional characteristics changed sensitively during the centuries. The result is a vast, heterogeneous and almost unexplored part of our built heritage. This paper focuses on the description of the coastal defensive system of the Pontifical State, concentrating on the geometrical, material and constructive characteristics of a particular structural typology: the 16th century watchtower. The aim is to establish an idealized model validated by historical information and in-situ surveys. A structural analysis is carried out, including a simple index analysis, linear dynamic and nonlinear static analyses. These analyses provide preliminary insights on the global mechanisms of failure and on the real behavior of the structure. Conclusions are drawn concerning the necessity of interventions in the perspective of an appropriate reuse of the towers which could endorse the restoration and maintenance bringing them to a new life.