Understanding the Damages Caused by the 1999 Kocaeli Earthquake on One of the Towers of the Theodosian Walls of Constantinople

The Theodosian walls of Constantinople have suffered many partial destructions in their long-lasting life, often because of strong seismic events, undergoing subsequent reconstructions. With reference to the 1999 Kocaeli earthquake, the article illustrates a procedure implemented to understand the damages suffered by one of the towers (tower 19) of this magnificent piece of heritage, that had just been partially reconstructed in the framework of a large manutention and preservation program of the whole historic defensive system. The seismic action on the tower was calculated considering local seismic site amplification, and the seismic behaviour of the masonry tower was analysed taking into account dynamic soil-structure interaction. Based on the available level of knowledge, the seismic demand of the tower is first evaluated by the classical modal response analysis and then by a linear time domain approach. Under both situations, the comparison between the compliant and the fixed base models allowed to recognize the detrimental effect of Soil Structure Interaction (SSI). Furthermore, the dynamic linear analysis allowed to detect the mechanism of earthquake induced triggering damage into the masonry panels.