Seismic fragility and energy efficiency upgrading of masonry compounds using lightweight aluminium alloy exoskeletons: a case study in South Italy

The seismic and energy retrofitting of existing masonry structures is a critical area of focus in structural engineering, particularly since a significant portion of the current building stock was constructed before the adoption of modern seismic codes. Consequently, these buildings not only lack seismic resilience but also experience considerable heat loss due to the use of materials with poor thermal performance. Recent seismic events across Europe, along with European directives, have highlighted the inadequacies of these structures and the urgent need for interventions that address both structural reinforcement and energy efficiency. Integrated solutions that simultaneously tackle these challenges offer a cost-effective and time-efficient approach to retrofitting. In this context, modern coating systems emerge as a promising alternative. By combining a metal frame base with thermal insulation materials, these systems enhance both seismic resistance and energy performance with minimal invasiveness. This paper explores the application of an external coating system, featuring aluminium alloy exoskeletons and insulating sandwich panels, to a masonry building complex in Castelpoto, a small town in the province of Benevento, located in the heart of the Campania region. The study first evaluates the performance of the existing compound through a macroelement modelling approach, followed by the arrangement of a lightweight retrofitting solution designed to improve the building’s seismic response and promote the box-like structural behaviour. The findings demonstrate that the integrated retrofitting system leads to higher safety factor values, which result in an overall improvement in seismic performance. These benefits are further confirmed by a fragility study, which shows a significant reduction in the probability of exceeding critical damage thresholds. The results highlight the effectiveness of the proposed solution in improving both seismic resilience and energy efficiency.