## 1 Introduction  
Insulating glass units (IGUs) are building components that show particular structural behavior. A typical IGU comprises two or more glass panes with a sealed gap filled with a low thermal conductivity gas (e.g., argon). Although such structures have many advantages from the point of view of the thermal protection of buildings, they show a particular structural behavior [1, 2]. The inability to equalize the pressure with the surrounding atmospheric air causes over- or under-pressure inside the gap [3, 4]. The phenomenon may result in the deformation of the panes under the influence of temporary or cyclical changes in weather conditions. In particular, an increase in atmospheric pressure or a decrease in gas temperature in the gap results in a concave or \"bulging\" form of deformation [5, 6]. The volume change resulting from the panes' deflection generates a pressure change in the gaps, whereby the external climatic load is partly reduced [3, 4, 7]. Thus, each IGU component pane is affected by the accompanying load resulting from the state of temporary equilibrium between the external climatic conditions and the gas pressure in the gap [8, 9]. Determining the operational load of the component panes was the primary goal of the analytical and numerical models described in the literature. In 1974, [PERSON] [10] proposed a method to determine the state of equilibrium in the IGU-environment system using the ideal gas equation and then to estimate the deflection and stress in the panes assuming a simply supported linear Kirchhoff plate. Milestones for analytical solutions were [PERSON]'s works, e.g., [3; 4], in which he defined the factors describing the reduction of the climatic load and gave the method of estimating the characteristic length of the IGU. The characteristic length is the IGU dimension at which the stress from climatic loads is largest. [PERSON] and [PERSON] [11] proposed a model for calculating deflection in multi-glazed IGUs based on numerical solutions of systems of equations. A numerically validated model for calculating static values in rectangular and circular IGUs was proposed by [PERSON] et al. [8; 9]. [PERSON] [6] presented an analytical and numerical model for estimating the deflection in a double-glazed IGU, also in the range of large deflections. [PERSON] and [PERSON] also proposed analytical load sharing models: in double-glass units, also triangular, based on [PERSON]'s method [1; 12], and in multiple units based on [PERSON]'s functions [2]. [PERSON] and [PERSON] analyzed the strength aspects of IGUs in the context of the duration of the load [13]. The same authors also investigated the effects of buckling on the behavior of double-glazed units [14]. In engineering terms, estimating the response of an IGU due to climatic loads is the subject of standard recommendations. The method of estimating climatic loads according to the European standard EN 16612:2020 [7] is primarily compatible with [PERSON]'s methodology [3; 4]. In addition, it includes guidelines on taking into account second-order effects (i.e., large deflections) and a simplified method of estimating equivalent thickness for laminated glass. According to the American standard ASTM E1300-16 [15], IGUs are designed assuming simply supported continuous conditions along four sides. To determine the proportion of the specified design load carried by each pane in the IGU, a method that maintains the ideal gas law equilibrium for the gap between IGU assembly and loaded conditions should be used. This problem was also analyzed numerically using the Finite Element Method (FEM). [PERSON] and [PERSON] [16] used plate theory and pseudo-elastic fluid elements to describe the complex interaction between the glass plates and the gas entrapped in the gap. [PERSON] and [PERSON] [17; 18] developed complex full 3D numerical models of an IGU, focusing on the actual mechanical properties and load-bearing mechanism for the involved components. Special attention was paid to the critical role of both primary and secondary sealant.