GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 Strengthening of a case-study colonnade: comparison between a traditional and an innovative glass-based seismic retrofitting technique C. Boni, G. Royer-Carfagni University of Parma, Department of Engineering and Architecture, Parma, Italy Introduction Historical buildings of our cultural heritage were designed mainly against gravitational loads, but may lack stiffness and strength against horizontal actions. Since these buildings are located in seismic areas, they can be at risk of collapse and represent a non-negligible hazard for users. As a general rule, a retrofitting plan must be aligned to three conservation principles: minimal intervention, authenticity and reversibility (ICOMOS, 2003). When the building displays an uneven distribution of structural stiffness, rebalancing is required. This can be pursued by providing additional stiff members in the compliant directions. The retrofitting can rely on strict material compatibility and solutions in alignment with the practice of ancient masons (Lourenço et al., 2019), in order to comply with the original monument. Anyway, there may be cases in which massive works should be avoided. Then, difference in materials is accepted provided that it is clearly recognizable and of minimal visual impact. Here, we analyse a particular case study, which is represented by an arcade gallery characterized by a soft storey supported by a colonnade. The seismic action can lead to a considerable deformation demand, which is usually not compatible with the equilibrium of the constituting structural elements, and to the shearing of the supported roof, prone to fall down. Our aim is to compare the traditional retrofitting technique of infilling a few fornices with massive solid walls, acting as additional buttresses, with a new technique relying on glass-based bracing (Boni and Royer-Carfagni, 2023). The advantages are that the bracing is prefabricated, stiff, slender and, most of all, transparent, recognizable and completely reversible. It can be designed to remain in the linear elastic phase under moderate earthquakes, so to avoid replacement costs, whereas the additional masonry walls are opaque and may undergo cracking during the shakes, thus requiring restoration works.