The mechanical performance of glass structures and load-bearing elements attracts the attention of several research studies, especially for those unfavourable or extreme operational conditions which may include possible degradation or even damage scenarios, and thus potential risk for customers. Severe damage and fracture of glass material for construction applications are typically regarded as accidental conditions which should be properly taken into account in design. Based on simplified considerations, it is assumed that any residual mechanical contribution of glass fragments can be fully disregarded. Glass fracture is in fact a rather complex phenomenon to assess and characterize, especially for existing structures, due to the combination of a multitude of influencing variables and unknown parameters. Knowledge and early prediction of possible damage is thus of utmost importance for these brittle elastic load-bearing elements. At the same time, the mechanical characterization of damage parameters can facilitate possible robust diagnostics and residual capacity estimates. In this chapter, the potential and feasibility of in-field vibration frequency estimates, which are known to represent a preliminary but rather important diagnostic parameter for general constructional members, is verified for various glass elements in damage and post-fracture regime. Recent applications of non-destructive experimental methods and dynamic identification techniques are discussed.
