Discussion of failure criteria and low-cycle fatigue performance of structural glazing connections under various seismic loading scenarios

In addition to static loads, structural glazing joints in glass and facade construction are often subjected to extraordinary loads such as earthquakes. This study investigates the load-bearing and failure behavior of structural glazing joints under low-cycle fatigue loading to address the current lack of reliable design methods and fatigue life curves (S-N curves) at high load levels. To evaluate the load-bearing behavior under low-cycle fatigue loading, force- and displacement-controlled fatigue tests were performed. To define failure criteria, especially for the displacement-controlled test, various cyclic parameters such as stiffness, dissipated energy density, and loss factor were analyzed. The fundamental parameter behavior exhibited notable similarities between the force- and displacement-controlled tests. Mathematical models derived from force-controlled tests provided failure limits which were applied to displacementcontrolled tests to determine fatigue life. The results demonstrated a strong influence of the failure criteria and a strong correlation between load level and cycles to failure, with S-N curves following the standard power law for high-cycle fatigue investigations and achieving high coefficients of determination (R2 >= 0.95). Key influencing factors, such as frequency and mean stress, significantly impact fatigue performance. A decrease in test frequency corresponded to a reduction in load cycles to failure. Testing under threshold loading conditions (R=0) resulted in an increased number of cycles compared to alternate loading scenarios (R=-1). The findings confirm the predictable failure behavior with cohesive failure mode for the structural glazing joints under seismic low-cycle fatigue loading, providing a foundation for reliable fatigue analysis. While the results are specific to the tested adhesive and joint geometry, they contribute to the development of a robust and economical design methodology for structural glazing joints under seismic conditions, advancing knowledge in glass and facade construction.