Climate loads in insulating glass units: comparison of theory and experimental results

The verification of insulating glass units in ultimate limit state often gives rise to the question of how to take into account the edge seal in the design of the glass panes. Usually the edge seal is calculated as immovable, as this is a more conservative assumption. A flexible edge seal, as to be expected under realistic conditions, leads to a lower climate load and therefore to lower stresses in the glass. In order to determine the influence of a flexible support on the verification of the ultimate limit state under the applicable standards in Germany, various setups of insulating glass units were subjected to cyclically recurring temperatures of -18 to +53 degrees C in a climate chamber. In this procedure, the atmospheric pressure was measured as well as the pressure in the cavity, as were the deformations of the edge seal orthogonally to the glass panes. Based on these, a comparison of analytical calculations of the climate load and the experimentally determined climate load is conducted. By means of the experimentally determined pressure difference in the cavity and the measured deformations of the edge seal, an effective spring stiffness in tension of the edge seal under the climatic test conditions was calculated using a finite element (FE) model. On the basis of an effective spring stiffness in tension assumed in a FE simulation, the influence of a flexible edge seal on the design of the glass panes is determined and discussed.