Past Experience

The behavior of the glass and frame system under cold-bending has been previ­ously studied on several projects. One of the first appearances of cold-bent glass in the architectural facade industry was in insulating-glass strip windows at the City Hall building of Alphen ann den Rijn in the Netherlands in 2002 [1]. Another Netherlands project constructed in 2002, the Floriade Pavilion in Haarlemmer – meer, used point-supported laminated glass panels cold formed on site to glaze three large openings in the pavilion. The cold-bent panels created a curved-glass surface matching the free-form exterior of the Pavilion [1]. In addition to build­ing facades, the smooth curved transitions between cold-bent laminated panels gave designers the freedom to create an undulating-point-supported glass roof for the Tramstation at Zuidpoort in Delft, Netherlands [2]. More recently this innovation was employed in the renovation of the Victoria and Albert Museum in London where the glass panels were cold worked on site to create a 4000-ft2 (370-m2) twisting roof over a previously unused courtyard space [2].

However, despite its growing presence in the international construction scene, this technology has been used sparingly in the United States. Concerns regarding long-term stresses and deformations induced on the glass and sili­cone by the cold-bending process as noted in prior research [1,3] may be one of the reasons for its sparse use. Nevertheless, the engineers and designers of these successful cold-bent projects and others were able to use various methods of finite-element modeling and physical experimentations to determine the struc­tural resiliency, code compliance, and warrantability of the curved glass [3-5]. From these analyses and testing, glass manufacturers developed enough confi­dence to warrant their glass products for use in cold-bending applications. However, the amount of cold-bending utilized in previous projects was rela­tively small compared to the bending performed during this research. This research seeks to gain a more complete understanding of the limits of the dura­bility of a cold-bent insulating-glass unit (IGU) under cold deformation by exceeding the amount of deflection previously used, and to assess the durability of such a deflected IGU.