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.
Mistral Tower: Value of System Design, Manufacturing and Installation in Cold Bent SSG Units
In cold‐bent Structural Sealant Glazing (SSG) systems, back‐flipping retention forces and differential displacements imposed to SG joints play a major role in the system design and need to be properly controlled. During last years, investigation on simplified equations to calculate cold bending stress into SG joints and tests to evaluate creeping and relaxation behaviour of Sikasil® structural silicones has allowed to identify where opportunities for systems optimizations are and to clarify that effective cold‐bending solutions cannot be uncoupled from new principles of system design, pre‐manufacturing and installation. The development of Mistral Tower in Izmir offers the chance to evaluate in detail the impact of different design solutions in combination with different production and installation methods and is used to present valuable options for approaching design of cold‐bent units effectively. The use of slim adapter frame bonded to glass units and free to slide into load‐bearing frame represents the basic requirement to limit cold bending effects on SSG joints, while minimizing production efforts. Valuable optimization results can be further achieved if bonding on either pre‐shaped frame or pre‐shaped frame/glass assembly is possible or if cold‐bending stress can be limited in time by a clever production method in controlled conditions. Advanced FE analysis simulating SSG joints by hyperelastic law confirms the influence that cross sectional depth of bonded profile has on stress introduced into SG joints due to cold‐bending.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.