Racking performance analysis of four-sided structural sealant glazing curtain wall systems through video capture technique

Full-scale unitized, four-sided, structural sealant glazing (4SSG) curtain wall system mockups featuring a re-entrant corner were subjected to cyclic racking displacements in accordance with the American Architectural Manufacturers Association AAMA 501.6 protocol to determine serviceability and ultimate behavior responses. Glass fallout, sealant adhesive or cohesive failure, and glass cracking were identified as limit states and corresponding drift levels were determined. This paper describes the details of the techniques developed and used for analysis and shows example applications of the method to mockups with racking test results available. The video analysis measured the changes in distances between glass and frame, which was then used to calculate an effective shear strain of the structural silicone by a linear and quadratic method. An effective shear strain of 173% and 130% was calculated from a linear method and a quadratic method for a structural silicone when failure initiated. Test data from the manufacturer indicates the ultimate shear strain of the structural silicone occurs around 200%.