On the vulnerability of ancient town walls to slow onset events: formulation of a synthetic index

Ancient masonry town walls are currently under threat due to several and diverse hazards. This contribution focuses on their vulnerability to slow onset events, including weathering conditions, environmental interactions, anthropogenic actions. The great extension of town walls allows for identifying the recurrent degradation and damage phenomena to create a portfolio of typical pathologies. The approach employs non-invasive technologies for the diagnostic of cultural heritage and introduces a tool to support decision makers in prioritizing restoration and retrofitting interventions, thus addressing preventive conservation. These tasks are extremely important for large-scale structures and for allocating economic resources that are often limited. Starting from the investigation of the current state of deterioration of a sample set of town walls in Tuscany, a specific survey form has been developed to support the evaluation of a vulnerability index. The application of the procedure provides a description of the typical degradation and damage phenomena affecting the town walls and a classification based on the synthetic vulnerability index .