Bonding of glass onto aluminium frames, known as Structural Silicone Glazing (SSG), has been active for more than 50 years on facades. Traditionally the silicone bite is calculated using a simplified equation described in guidelines such as ETAG002 or ASTM C1401, which assumes a homogenous stress distribution along the sealant bite. Although this approach will remain a valid method for which there is proven performance, recent research has indicated that joint dimensioning can be optimized for excessively large joint bites such as projects that are being designed to perform in high velocity wind zones. As joint bite dimensions increase, the distribution of stress in the structural silicone sealant diverges from homogeneity in mostly tension, under negative windload. This divergence is due to the rigidity of the sealant as a function of glass rotation, where mixed modes of stresses can be observed in compression, tension and shear along the width of the silicone bond. Alternative methods of compliance to the conventional design techniques are important as they allow a greater design freedom without sacrificing long term durability. Physical prototypes from small scale H-pieces to full scale panels measuring 914mm by 1524mm were tested with different joint aspect ratios varying between 2:1 to 4:1 width to depth ratios. Finite element analysis of the tested units also provided insight into the behaviour of sealant distribution and potential failure identification. Based on the performed testing, new methods of compliance for dimension joints are proposed beyond normal conventional methods outlined in ETAG002 and ASTM C1401.
Advanced engineering methods unlock higher permitted stresses for structural glazing designs
Company: Dow Silicones Corporation, Elizabethtown, KY, USA
About the speaker:
Jon Kimberlain currently provides technical expertise and application support for Dow Silicones as a Senior TS&D Scientist. With 24 years with Dow Corning and Dow Chemical, Jon has published 25+ research papers on the use of silicone sealants in high performance buildings which have been presented at venues such as Façade Tectonics, ASTM Symposiums, GlassCon and GPD Finland. Currently a founding board member of Architectural Glass and Metal Certification Council and board of Façade Tectonics Institute, he has also been active in leadership with Glass Association of North America and National Glazing Association.