"Historically, the role of glass is one of, if not the single most important material component common to most of the major works of modern architecture. Cold bending of glass, much more affordable than heat bending, uses brute force (and a little math) to calibrate the deformation of a planar sheet in the service of a larger design objective.One of the challenges for architects with this approach of cold bending is that although one can perform distortion analysis on the geometry of the panels, there are no widespread standards which help clarify how much bending is "too much". What is the relationship of size to potential deformation? Most important for the long term occupant/owner, how does this process impact manufacturers warranties on these assemblies? The purpose of this study is to explore the limitations of the material and its subsequent implementation on two projects in China--both of which have used cold-bent glass in different ways in a 300 meter tall office tower. Although the structural performance of the glass itself might seem like the more logical focus of a research project on cold-bending, the guiding principles that addressed the warrantability of such applications focused on the additional pressures exerted upon the sealants, not the glass. The primary seal may be more durable than previously assumed. Informally-defined constraints within the profession suggested that a typical full size panel (5 feet wide, 1-storey tall) should not be bent more than about 4" out of plane, but in our testing, for a panel that was bent the equivalent of 12" out of plane, the primary seal did not fail under long-term testing. The practice of cold-bending glass still needs a great deal of study. However, with the research now published by ASTM, we hope it will prompt further research efforts."
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