Large Scale Seismic Vulnerability Assessment of Historic Urban Areas using the Applied Element Method

Recent seismic events in European countries highlighted the vulnerability of the historic part of many European cities. For example, the August 2016 earthquake in Italy caused significant damage to numerous historical buildings in the villages of Accumuli, Pescara del Tronto and Amatrice while only limited damage was reported in the newer part of the cities. Damage was worst in villages that consisted of ancient masonry structures; local authorities reported damage to 50% of the buildings in Amatrice. The fragility of the masonry structures combined with the reduced dimensions of roads and the blockages created by some collapses slowed down the emergency response teams and increased the need for additional precautions and preventive actions in order to avoid disproportionate economic and life losses. Although several analysis tools were developed for evaluation of single masonry structures, the simultaneous analysis of historic urban areas as well as the detection of critical buildings that, if collapsed, could cause roads interruption and additional damage to the surrounding structures remains an open challenge for computational methods. If achieved, the analysis could assure the efficiency of targeted retrofitting actions and significantly increase the resilience of the urban system by optimizing the use of available economic resources. One of the main constraints of the study of these types of structures is the need to consider the interactions between aggregated buildings, both during the seismic event and during the collapse. The numerical tool must also have the ability to implement automatic separation between the elements of the structures. Moreover, these heritage buildings have complex structural details such as presence of buttresses, arches and vaults and interaction between structural elements with different types of connections. This type of high fidelity modeling requires enormous amount of computational resources due to the required high element’s discretization, especially when the objective is to model large areas or entire neighborhoods. The work described in this study analyzes the most recent application of the Applied Element Method in the analysis of historic urban areas, with particular focus on the simulation of masonry and heritage structures. Recently published studies highlighted the capability of the method to overcome the limitations of the current structural analysis techniques, both in terms of results accuracy and in terms of use of computational resources [1]. A case study, for a portion of the historic center of the city of Roquebillière, France, has been simulated and assessed within the European Project “INACHUS” identifying target-retrofitting actions, and demonstrating the practicality of using this technique to evaluate the accessibility of strategic roads for rescue operations. The analysis allows the development of a proper emergency plan in case of seismic events and results in an increase of the resilience of the urban system