Damage States of Structural Silicone Glazed Facades

Abstract

Unitized curtain walls play an integral role in contemporary architectural designs, offering advantages such as lightweight construction, high quality control and ease of installation. However, recent post-earthquake surveys have revealed their vulnerability to damage, raising concerns about potential hazards in post-earthquake scenarios. Even slight-to-moderate damage can lead to loss of functionality and economic losses, arising from breaches in the air/water tightness of the building envelope and costly repairs/replacement. Furthermore, as the damage progresses from moderate to severe, it poses a life-threatening risk to occupants and pedestrians due to falling glass or debris from the damaged façade. Among the different types of unitized curtain walls, structural silicone glazing emerges as a resilient assembly system with the potential to enhance the seismic performance of the façade. Nevertheless, despite initial studies on the seismic behaviour of the silicone bonding sealant, research in this field remains limited. Typically, experimental investigations overlook the analysis of the complete sequence of damage states and the ultimate resistance of the various components within the silicone-bonded façade. As part of a broader EU-funded research project, this paper presents the key findings derived from an experimental campaign on structural silicone glazed facades conducted at the Permasteelisa Group laboratory. The overall research aimed to gather information on the post-earthquake functionality and the failure modes of alternative façade designs. The hierarchy of damage mechanisms that occur during an earthquake was established by testing full scale façade prototypes with different pane and silicone joint dimensions, frame displacement capacity and loading mode. The testing procedure involved a series of in-plane displacement-controlled crescendo tests, time histories and monotonic testing, gradually increasing the intensity levels to evaluate the progressive damage states within the façade system. The paper provides the main outcomes derived from both damage observations and data post-processing, including the assessment of utilization factors and fragility curves for the façade components. These results offer valuable insights into the seismic behaviour of structural silicone glazed facades, thereby supporting the future development of design guidelines and practices for more resilient facade systems.