Optimal cold bending of laminated glass

Abstract

a b s t r a c tCold-bending of laminated glass panels, by forcing their contact with a constraining frame, is a promising technique for free-form glazed surfaces. Their static state varies in time due to the viscosity of the polymeric interlayer, which causes the decay of the shear-coupling of the constituent glass plies. The direct problem consists in calculating the spatial and temporal evolution of stress after cold-bending. Considering an equivalent secant elastic shear-modulus for the interlayer to account for its viscoelasticity, various conditions for cylindrical deformations are analyzed in detail. A ''conjugate-beam analogy'' is proposed for the inverse problem, i.e., to determine the deformed shape that, at a prescribed time, provides the desired state of stress. Remarkably, the simplest constant-curvature deformation, often used for cold bending, produces high shear stress concentrations in the interlayer with consequent risks of delamination. For the same sag, better linear or cubic distribution of shear stress are attained with slightly different deformations, compatibly with glass strength. Among the considered cases, the optimal configuration is sinusoidal, because it provides the smoothest distribution of shear stress with inappreciable geometric differences with respect to the circular shape.

Transformable Curved Thin Glass Greenhouse

“…Cold-bending, consisting in forcing in the desired position initially-flat glass elements, so to produce the curvature through elastic straining, allows for the construction of curved elements forming free-form glazed surfaces. The simplest forms that can be obtained through cold-bending are single-curvature surfaces as well as double-curved anticlastic surfaces (Galuppi and Royer-Carfagni, 2015c), whose degree of curvature can be easily modified through a slight variation of the constraining actions. Cold-bending technique is extensively used also for insulating glass units (see, among the other, (Eekhout and Niderehe, 2009;Bijster et al, 2016)).…”

“…Furthermore, the traditional curved glass obtained through hot-bending is being replaced by cold-bent glass. Cold-bending (Belis et al, 2007;Galuppi and Royer-Carfagni, 2015c) and coldlamination-bending techniques Galuppi and Royer-Carfagni, 2015a) are increasingly developing because they do not need any negative template and this leads to consistently lower costs with respect to hot bending.…”

Study on the mechanical response of anticlastic cold bending insulating glass and its coupling effect with uniform load

“…By this technique, the number of problems about bad optical quality, probably as a result of permanent deformation caused by heat bending, is significantly reduced [ 7 ], which is due to the cold-bent glass is always reversibly deformed as demonstrated by curvatures within the elastic range. Furthermore, cold bending is advantageous in terms of low cost [ 9 ], low energy consumption, environment friendliness, and short time of production [ 8 ]. It has been applied in many engineering projects, such as Strasbourg Railway Station in Alsace, France [ 9 ]; Victoria & Albert Museum in London, UK [ 7 ]; Christoph Dengler Seele glass bridge in Germany [ 10 ], etc.…”

Experimental Study on Single Corner Cold Bending Mechanical Response of Laminated of PVB Interlayer Tempered Glass Panes and the Coupling Effect with Load

“…Under the applications of practical engineering, researchers began to study the stress of cold-formed glass panes. Laura Galuppi et al [10][11][12] studied the failure limit of unidirectional cold-formed laminated glass panes, the distribution of interlaminar shear stress and the influence of the cold bending shape and conducted a unidirectional cold bending experiment. Kyriaki Corinna Datsiou [13] studied the cold bending limit of a single glass pane by experimental and numerical simulations.…”