Mistral Tower: Value of System Design, Manufacturing and Installation in Cold Bent SSG Units
Use of cold-bent and warped glass units in unitized curtain walling is becoming a state-of-the art application. During the last years, such a global trend has challenged the design and engineering of glass units, frame elements as well as bonding joints in Structural Sealant Glazing (SSG) applications and has pushed for the investigation of material performance and calculation concepts, beyond available standards and guidelines. It is clear today that in SSG systems cold bending retention forces and differential displacements play a major role in the system design and need to be properly controlled. With reference to SSG joints, investigation has focused on proposing simplified equations to evaluate cold bending stress and studying relaxation and creeping behavior of Sikasil® structural silicones to exploit material performance beyond standard limits. Such investigation process allows identifying where opportunities for systems optimizations are and clarifies 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 frame solutions in combination with different production and installation methods and is used to present to system designers and façade producers valuable options and guidelines 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 material law validate preliminary stress evaluation, criteria selection for unit manufacturing and final design choices in Mistral Tower construction.