Cold bending of vertical glass plates: Wind loads and geometrical instabilities

The study investigates the mechanical response of glass shells cold bent into hyperparaboloid shapes used in building technology. Focus is addressed on two subjects: the application of the cold bending procedure to vertically oriented rather than horizontal plates, which allows to minimize the disturbance produced by the initial deflection due to self-weight, and the effect of wind load on curved glass panels installed in glazing façades. The particular case of a vertical monolithic glass plate (2000 × 2000 × 10 mm) loaded symmetrically on two diagonally opposite corners is studied experimentally and numerically, developing a finite element model, and the results compared each other. Both experiments and numerical analyses show that a mechanical disturbance, introduced e.g., on the centre of the plate, promotes a change in the deformation mode during the bending process. Geometrical instabilities which impair the optical quality of the glass, and trigger a serviceability limit state failure, are evidenced. A parametric analysis is conducted to investigate the influence of the size and the aspect ratio of the glass plate on the cold forming procedure. The examined response parameters include the geometrical distortion of the glass plate, involving the possible occurrence of optical distortion and the maximum tensile stress in the plate. In the second part of the study, the effect of wind load on curved glass shells is numerically evaluated. The results point out the possible trigger of a limit equilibrium stability, with a“snap-through” transition from an equilibrium state to another non-adjacent equilibrium configuration which can result in a sudden break of the glass plate. This phenomenon is affected from the size of the glass plate and the curvature imposed to the plate during cold bending. The proposed methodology could represent a convenient tool to assist practitioners in selecting the appropriate thickness of façade glass panels.