In cooperation with the company Seele (Gersthofen) the IBK Research + Development is engaged in a development study with new glass constructions around the potential of lamination technology with high performance foils. Here the worldwide leading company for all-glass facades and glass constructions has been setting new standards for years. The aim of the development studies is to combine very thin glass layers by means of a high-strength laminating film to form two-dimensionally curved high-performance glass. The potential of this product will be demonstrated with the all-glass bridge at the 'glastechnology - live 2008' and presented to the public. The innovative product 'glascubond' was secured by the Seele company in the course of the project.

Float glass is produced in the glass industry in flat plates with the dimensions of 6.00 x 3.20 m. These plates are, due to their small thickness (4-12mm), flexible. The elasticity of the glass panes depends on their thickness. Their behavior is similar to that of sheet metal, with one significant difference. Sheets can be deformed without the application of heat, in the case of glass, deformation beyond the yield point leads to glass breakage. Therefore

Until now, it has been state of the art to hot-form flat glass sheets, i.e. the glass sheets are heated in a furnace above 640°C, the glass structure loses its strength and plastically forms itself into the desired shape. Disadvantages of this technique are the cost of the mould, the size limitation due to the bending furnace, the optical impairments caused by the thermal process and the inaccuracy when the glass cools down. In contrast, the structural glass elements of the all-glass bridge for 'glasstechnology live 2008' make consistent use of the elastic range of the brittle material glass for the construction of the curved glass surfaces. For the first time, the potential of 'cold-bent' glass panes in structural glass construction was tested and proven.

The running plate of the bridge consists of seven 4 mm thin float glass panes and six 1.5 mm thin highly transparent SGP (Sentry-Glas-Plus) films from DuPont. Before the lamination process, the flexible glass panes are placed on a mould as a glass package. Due to their own weight and low inherent rigidity, they lie on this mould without any additional energy input. The lamination process freezes the internal stresses and the individual glass sheets are rigidly connected to each other via the foil. Thus, the internal stresses can be used positively for the overall construction. An interesting aspect here is a completely new volume ratio of glass to laminating films. The volume ratio of the running surface of the bridge is 3:1 (glass to SGP), which naturally reduces the dead loads of these glass components.

The bridge consists of three arched girders in the form of cold-bent glass plates with dimensions of 2 x 7 m for the running surface and 1.2 x 7 m for the parapets, with the corresponding cut-to-size pieces. The joining of the two-dimensionally bent sheets results in a three-dimensional body that optimally counteracts the respective loads. The running surface forms a slender arch girder and transfers the traffic loads of 5 KN/m2 into the supports. The parapet surfaces form an arch against the impact loads of 1 KN/m2 to be absorbed. The bonding of the three panes in the area of the running surface, with a height of 37 mm, counteracts the unequal loads and prevents the overall construction from bulging. This joint can be loosened with a 'cutter cut' for disassembly, similar to the force-locked glued-in windscreens in automobiles. If necessary, this process can be repeated several times, so that the entire construction can be reliably assembled and disassembled. The all-glass bridge exhibit sees itself as an innovation carrier for a completely new approach to the material glass. Flat "standard" float glass panes are transformed into a three-dimensional, maximally transparent and accessible glass body by deformation under dead load and an "intelligent" two-dimensional cut.

Duration: 2008   
IBK2 I Research + Development
seele GmbH & Co. KG