Optimizing methodologies for cold bending of glass


Modern free form glass architecture has become increasingly popular in the structural sealant glazing application, as demonstrated by many iconic building projects, such as Allianz tower in Milan. Amongst the different technologies to manufacture such glass, cold bending is one of the most cost efficient and aesthetically pleasing solutions. In this process, flat glass panels are elastically deformed to follow the façade contours by bonding to a metal frame with a silicone sealant. This operation imposes a permanent bending force onto the silicone as the bent glass strives to return to its initial flat shape. This can lead to silicone creep and tear failure if the joint is not properly dimensioned. Previous research by the authors has evidenced through a combination of experimental testing and finite element analysis, how principal strain in the sealant needs to be limited to ensure durability and avoid tearing. This current research proposes an optimized methodology for cold bent glass and SSG design through a simulation-based DOE study for different glass and metal frame form factors as well as silicone sealant parameters. In addition to the level of cold bend glass deflection, the metal frame and sealant thickness have the most significant effect on the peak strain in the sealant during the cold bent glass operation. Two solutions are proposed to improve the silicone sealant durability and reduce creep deformation.




New model for performance of silicone bonded facades during seismic events


Some of the world’s largest metropolitan areas are located within highly active seismic regions. Earthquakes can lead to major architectural and human impact, especially when glazed curtain walls are involved. Silicone structurally glazed façades are a durable assembly system, known to optimize the envelope’s weatherproofing performance and aesthetics, (removed  but) which can also potentially contribute to a better seismic resistance of the building’s façade.

This paper presents the seismic study of silicone bonded glass curtain wall systems, combining both finite element analysis and experimental validation. Applying finite element analysis to silicone requires appropriate material models which suitably mimic the typical loading undergone during specific events. In the case of earthquakes, repetitive loading cycles occur, which can highlight the stress relaxation behavior of silicone elastomers. The material model developed was validated using both test results obtained inhouse on mid-scale build-ups and results of the experimental campaign carried out at the laboratory of Permasteelisa Group on full-scale unitized curtain walls. These tests considered varied silicone types (Young modulus) and joint dimensions (width and thickness or aspect ratio) and allowed identifying criteria for failure prediction and suitable design strength values as well as joint dimensioning guidelines optimizing a response to seismic events.