Considerations on efficient procedural steps for seismic capacity assessment and diagnostics of historic structural glass systems

Structural designers are nowadays supported by standards and guidelines to optimize the mechanical performance and safety level of glass load-bearing elements and assemblies in buildings. Key role is given to deformation and stress check, and post-breakage verification, for newly designed glass systems. Performance limits are provided also for extreme events, such as earthquakes. Besides, major risk for people could derive from existing/historic glass components and systems that have not been conceived to offer minimum structural capacity against operational loads and accidents. No technical recommendations are available to quantify their actual vulnerability and capacity, thus retrofits and mitigations are also hard to plan. In this paper, possible procedural methodology steps towards are addressed. The attention is given to present technical guidelines for structural design, on one side, and on the optimized use of non-destructive methods (like Operational Modal Analysis (OMA)) and numerical methods to facilitate diagnostic steps and the mechanical characterization of components, as well as to realistic description of boundaries and even damage. Practical examples are discussed for a case-study glass-steel envelope built in 60s in Italy, which is analyzed with the support of Finite Element (FE) numerical models against in-plane and out-of-plane seismic actions.