Vulnerability assessment and dynamic characterisation of a glass footbridge: on-site vibration tests and FE numerical modelling

In the last decades, the use of glass as a load-bearing material showed an exponential increase, both on the side of projects and research studies. Although it represents a relatively new construction material, requiring appropriate design methods and knowledge, glass is largely used for facades, roofs, footbridges. Given a series of intrinsic features, special care should be spent at the design stage, to ensure appropriate fail-safe requirements, but also in the life-time of these structures (Haldimann et al. 2008). The brittle behaviour and limited tensile resistance of glass, as well as the typical high flexibility of glazing assemblies, represent the major issues. Further critical aspects may derive from time and ambient effects, due to the sensitivity of glass-related materials and components to long-term loads, humidity, fatigue, etc., or extreme loads. The vulnerability assessment of glazing systems under exceptional loads (seismic events, fire, etc.) is hence an open topic, still requiring huge efforts. In this paper, the preliminary dynamic characterisation of an existing glass suspension footbridge is presented. As a casestudy, the walkway of the Basilica of Aquileia (UD) is taken into account. On-site vibration experiments are discussed, to estimate the fundamental parameters of the structure. A Finite Element (FE) numerical study is then carried out, to further assess and explore the walkway performance.