Next generation structural silicone glazing
This paper presents an advanced engineering evaluation, using nonlinear analysis of hyper elastic material that provides significant improvement to structural silicone glazing (SSG) design in high performance curtain wall systems. Very high cladding wind pressures required in hurricane zones often result in bulky SSG profile dimensions. Architectural desire for aesthetically slender curtain wall framing sight-lines in combination with a desire to reduce aluminium usage led to optimization of silicone material geometry for better stress distribution. To accomplish accurate simulation of predicted behaviour under structural load, robust stress-strain curves of the silicone material are essential. The silicone manufacturer provided physical property testing via a specialized laboratory protocol. A series of rigorous curve fit techniques were then made to closely model test data in the finite element computer analysis that accounts for nonlinear strain of hyper elastic silicone. Comparison of this advanced design technique to traditional SSG design highlights differences in stress distribution contours in the silicone material. Simplified structural engineering per the traditional SSG design method does not provide accurate forecasting of material and stress optimization as shown in the advanced design. Full-scale specimens subject to structural load testing were performed to verify the design capacity, not only for high wind pressure values, but also for debris impact per ASTM E1886 and ASTM E1996. Also, construction of the test specimens allowed development of SSG installation techniques necessitated by the unique geometry of the silicone profile. Finally, correlation of physical test results with theoretical simulations is made, so evaluation of design confidence is possible. This design technique will introduce significant engineering advancement to the curtain wall industry.
Structural silicone glazing: optimizing future designs based on historical performances
ABSTRACT This article highlights the advantages of structural silicone use on a smart façade for attaching glass that is part of a curtainwall or window wall glazing system. This is written for the façade engineer/designer so that maximum performance can be designed into the envelope to maximize transparency, thermal performance, and natural and manmade impact performance, while maintaining the integrity of air infiltration, water infiltration, and structural performance. References are provided for the façade engineer/designer to allow a deeper literature search for validation of performance. Fifty years of in-service structural performance and experience has shown this system is extremely durable. Reviewing the standards that exist today helps one understand past success while also paving the way to the future. Design tools for façades now include finite element analysis that can analyze structural silicones for the hyperelastic properties that they possess, acting in conjunction with framing and glazing assemblies. Thermal analysis of the system in the design phase in conjunction with material selection can provide a pathway for optimizing thermal performance and condensation resistance of the façade while maximizing transparency.
Seismic Performance of Stick-Built Four-Side Structural Sealant Glazing Systems and Comparison With Two-Side Structural Sealant Glazing and Dry-Glazed Systems
A research project was undertaken to study the simulated seismic performance of mock-ups of a full-scale, four-side structural sealant glazing (SSG) system. “Stick-built” mock-ups were subjected to cyclic racking displacements in accordance with the American Architectural Manufacturers Association (AAMA) 501.6 test method. Although the test method focuses on glass fallout, drifts associated with serviceability damage states, such as sealant adhesive or cohesive failure, and glass cracking were also identified during the conduct of the tests. Damage to sealant joints was tracked as a function of drift level using visual and video inspections of weather-seals and structural-seals and air-leakage tests. Data from this study are compared with data collected from similar studies on comparable two-side SSG and dry-glazed mock-ups. Contact with panels diagonally above and below a given glass panel at panel corners was found to be the likely cause of initial sealant damage, glass cracking, and glass fallout as opposed to glass-to-frame interactions for two-side SSG and dry-glazed curtain-wall constructions. Thus, modified corner geometries and/or joint dimensions can be used to delay (i.e., shift limit states to higher drift levels) or avoid these damaging panel interactions. Mock-up specimens were also instrumented extensively so that real-time glass-panel translation and rotation, and weather-seal deformation measurements could be recorded. A summary of these measurements is presented and discussed in the context of their follow-up use for informing the development of damage prediction models for SSG curtain walls during seismic loadings. The study shows that stick-built curtain walls with four-side SSG configuration are expected to have higher drift capacity compared to two-side SSG and both are expected to have higher drift capacity compared to dry-glazed configurations.