Abstract
Continuously curved, highly transparent façades or roofs are increasingly demanded in architecture. Regularly curved or free-form building envelope shapes represent a rapidly growing market field in construction and project design. For such transparent roof or façade claddings, the necessary durability, strength and safety require laminated safety glass as the principle material. Whereas the faceting of curved surfaces to apply planar glass elements is a frequently used cladding solution, the employment of curved glass modules permits a more precise, smooth achievement of curved envelopes. Recent improvements in the industrialised fabrication of curved glass render the use of such elements increasingly attractive. The two main, but different, production methods to shape these modules are the heat bending and cold bending of glass. Plastic heat bending results in a stable glass shape permitting high curvature. However, any potential optical surface bumps, any remaining irregular local interior stress from production and the limited applicability of toughened glass impose restrictions on the use of heat bent glass.
In contrast, elastic cold bending only allows for low curvature but provides high optical surface quality and Permits the unrestricted use of toughened glass. Stabilisation of the curved shape of cold bent glass without a retaining substructure can be achieved through the establishment of a shear compound of several elastically bent glass
panes via lamination with polymeric interlayers. The bending stress remains in the glass. Despite the potential of this type of cold bent glass for construction purposes, comprehensive research approaches and the necessary stress- and shape-monitoring methods for glass laminates are lacking. Therefore, the characteristic properties
and parameters influencing manufacture, the short- and long-term behaviour of cold bent glass, applicable numerical form-finding models and shape- and interior stress-monitoring methods have been investigated in the present work. The testing of real scale cold bent glass specimens with respect to displacement and stress permits the verification of the analyses. Close range photogrammetry has been applied to measure the threedimensional shape and recovery behaviour of bent laminates. A new method for permanent real-time Monitoring of the interior stress in the laminate by applying thin, barely visible, fibre-optical Bragg-grating sensors with transparent adhesive bonding has been developed. Fibre optical sensing has been examined and evaluated and is discussed as a possible monitoring system applicable to multi-layered glass units. Based on the accumulated modelling and testing results, information regarding the behaviour and the design of cold bent laminationstabilised glass and the potential of fibre-optical monitoring for glass laminates is provided as a working basis in the conclusion to this work.
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