Glass Structures Subjected to Seismic Excitations

Nowadays, glass structures are increasingly common in buildings' envelopes and the current design is moving toward point supported glazing systems (PSGS) for aesthetic and energetic reasons, among others. However, the research on the topic is scarce despite much damage has been recorded during the last decades due to seismic events. It has also been observed failure of glass panels due to small seismic events even if they had resisted more hazardous ones before. For these reasons, the research work analyses the behaviour of PSGSs when subjected to seismic loadings with the intent of describing both instant and long-term behaviour.
The study is performed by Finite Element (FE) modelling of a 4-storey building equipped with a PSGS and horizontal glass fins and subjected to a set of 6 Strong Ground Motions recorded by an accelerograph in California over an 18-year period.
Analysis of the stress histories is performed to describe the system capacity with a comprehensive approach which includes both instant and long-term effects. In fact, not just the instant (inert) glass strength is considered, but also its time-dependent property (self-fatigue phenomenon) which makes the glass a material that may accumulate damage.
Results show that the apparent increase in strength for short-duration loadings may provide the glazings with sufficient capacity, but in the event that the external stress is slightly smaller than the inert strength, some damage in the glass is induced with the effect of a reduction in capacity. A practical and simplified example shows that the glazing lifetime could be reduced to 35 years instead of the expected 50 years due to prior seismic excitations.