Testing of Bonded Glass Facade Elements under Cyclic Loading and Large Deformations

Abstract

Structural Sealant Glazing (SSG) facade systems are exposed to significant deformations under extreme wind or seismic loading in certain regions, while current design standards only insufficiently capture the cyclic behavior of bonded systems subjected to large deformations. In this study, large-scale component tests were conducted on three-panel glass facade assemblies with vertically coupled SSG joints. The specimens were subjected to cyclic in-plane displacements using an electromechanical actuator at a frequency of 0.5 Hz to simulate interstory drift. Several load levels with up to 100 cycles were applied, generating shear levels in the horizontal joints of 0.25 tan(γ), 0.50 tan(γ), 1.00 tan(γ) and 1.20 tan(γ), followed by increasing amplitudes until failure. Monolithic glass panes and laminated glass (LSG) with thicknesses of 10 mm, 20 mm, and 30 mm were investigated using corresponding joint geometries. The experimental setup included force and displacement measurements, inductive sensors, and digital image correlation, enabling the evaluation of both global system responses and local joint deformations. The results reveal a pronounced amplitude-dependent, dissipative hysteretic behavior accompanied by significant stiffness degradation. At low and moderate shear levels, the systems remained stable, exhibiting nearly constant dissipated energy and secant stiffness, while the Mullins effect diminished rapidly. Damage initiation occurred only at high shear levels, characterized by saw-tooth-shaped crack propagation and eventual tearing of individual joints, without sudden failure or glass fallout. Increasing the width of the vertical joints led to a marked increase in global stiffness and a concurrent shift of deformation demand toward the horizontal joints. Overall, the results highlight the complex, damage-sensitive structural behavior of bonded SSG facade systems under large-amplitude cyclic loading.