Insulating glass units (IGUs) are widely used in glass curtain wall systems (GCWSs) due to their energy efficiency and daylighting benefits. However, premature failures caused by environmental and mechanical factors remain a major concern. Existing quantitative analysis and finite element (FE) modeling methods are also insufficient to capture the multi-factor degradation of edge-seal watertightness under real service conditions. This study presents a comprehensive approach to evaluate the degradation of a key durability indicator, the moisture-resistance time (Tm), under coupled effects of temperature, humidity, ultraviolet (UV) radiation, and shear strain. A total of 219 lab-fabricated IGU strip specimens were subjected to a 4000-hour artificial accelerated aging (AAA) test to provide first-hand experimental data. Based on these results, a hierarchical aging model (containing two primary parameters and sixteen secondary parameters) was developed using a phenomenological approach combined with a naive Bayes framework, with parameters estimated via the Markov Chain Monte Carlo (MCMC) method. A recursive prediction method incorporating local hourly meteorological data and the principle of UV-dose equivalence was then applied to simulate multi-year degradation under realistic service conditions. Results indicate that moisture-resistance time can decrease by over 60% under severe aging conditions and may decline by approximately 24% over three years in Beijing, with seasonal variations in degradation rate. The predicted service life of qualified IGUs in Beijing is approximately 14.4-17.1 years, providing a quantitative basis for durability assessment, maintenance planning, and performance-based design optimization.

Accurate and efficient evaluation of the load-bearing performance of multi-glazed insulating glass units (IGUs) under uniform loads is essential for wind-resistant design and safety assessment of glass curtain wall systems (GCWS). However, existing empirical data and numerical models are insufficient for reliably capturing the mechanical behavior of these novel thin-shell components, particularly for large-deflection analysis. This paper presented and validated two different finite element (FE) modeling methods, considering geometric nonlinearity, material nonlinearity, and uneven load sharing. Simply Supported (SS) and Center Constrained (CC) boundary conditions were used to build three FE models. Their accuracy, computational efficiency, and applicability were discussed and compared with the BAM method. Based on the superior 2-CC method, the effect of cavity thickness on load sharing ratios (LSRs) of quadruple glazed IGUs (QIGUs) was analyzed. It is found that the LSRs vary with load magnitude, and for the currently used Type A product, designing based solely on the stiffness distribution method adopted by the ASTM E1300 may lead to an underestimation of the LSR for Pane 1 by over 30 %, while overestimating the LSR for Pane 4 by nearly 50 %. Furthermore, a parametric analysis was conducted to determine the LSRs for ten types of market-available QIGUs, as preliminary improvements to the stiffness distribution method. Finally, an optimized calculation formula was presented, providing a basis for conventional QIGU design and a reference for future lightweight optimization analysis of multiglazing components.

Precise and rapid calculation of insulating glass units (IGUs) under climate load is crucial for the determination of the durability, aesthetics, and safety of curtain walls during the early design and subsequent service stages. However, available empirical data and numerical simulations are inadequate in accurately evaluating the temperature field and the temperature-induced mechanical behavior of this energy-saving building material, especially the in-plane thermal shear deformations of Polyisobutylene (PIB) and the out-of-plane deformation of the glass panels. In this paper, three pieces of IGUs were used in heat transfer tests to obtain the temperature and displacement fields. Two finite element (FE) models were built based on sequential thermo-mechanical coupling simulation and the calibration approach of the Ideal Gas Law. The applicability, accuracy, and computational efficiency of the models above were compared. A simplified piecewise-linear model for rapidly calculating the temperature field along the thickness direction was proposed by MATLAB surface fittings. Based on the deformation mechanism, the contribution ratios of two main influencing factors to deformations were defined. Simplified calculation formulas applicable to the in-plane thermal deformation of PIB, and the out-of-plane deformation of glass panel were proposed with the coefficient of determination R2 over 0.99, considering the temperature difference of indoor and outdoor environment, rectangular dimension, and the thicknesses of pane and airspace. In addition, the mutual constraint effects were presented and defined in this paper. The detailed analysis of thermal deformation lays the groundwork for further addressing premature failure issues and optimizing edge bond constructions of IGUs.

Precise and rapid evaluation of the temperature field in tripled-glazed insulating glass units (TIGUs) under intense solar radiation is crucial for the thermal-resistant design of glass curtain wall systems (GCWSs) and assessments of building thermal environments. However, available empirical data, traditional Tsol-air method, and numerical simulations are inadequate in accurately calculating the thermal behavior of this emerging energy-efficient building material, particularly for the complex heating effects of direct and diffuse solar radiation and the thermal convection of cavity gas in multilayer glazing systems. This study presents a comprehensive thermal analysis of TIGUs using a refined thermo-fluid-structure interaction (TFSI) finite element (FE) model that accounts for heat conduction, convection (both external and within cavities), and radiative transfer. The improved model, implemented in ANSYS and incorporating D-O radiation, k-epsilon (RNG) viscous, and energy models, demonstrates superior agreement with experimental results and the WINDOW software (MAPE = 2.45%), which addresses key limitations of existing standards and the Tsol-air method. A parametric study based on meteorological data from ten representative cities was conducted, identifying the influence of outdoor temperature, direct radiation, and diffuse radiation on the TIGU temperature field, with their effects quantitatively characterized by sensitivity coefficients a, b, and C. The concept of "peak region" was introduced to intuitively describe the non-monotonic thermal behavior under strong solar radiation. For the widely used configuration (6+12Air+6+12Air+6 mm), fitted equations were derived using least squares and Lagrange interpolation methods, with R-2 > 0.99, enabling efficient estimation of temperature distributions under long-term climatic conditions.

Polyisobutylene (PIB), commonly used as the primary sealant of double, triple, and multi glazed insulating glass units (IGUs), provides the key moisture barrier function and determines the expected lifespan of the IGUs and even the entire glass curtain wall systems (GCWSs). Slipping and debonding of the PIB, caused by temperature changes, have resulted in numerous instances of premature failure of building envelopes. However, available research is inadequate in accurately evaluating the service environment of IGUs and thermal-deformation behaviors of this energy-saving building material. This paper presented a simplified method for analyzing the thermal environment of IGUs, considering outdoor air temperature, solar radiation, wind speed, and angle to the horizontal. A numerical modeling method was proposed and validated with the heat transfer tests. Three finite element (FE) models were built and utilized for the precise analysis of temperature-induced deformations of double, tripled, and quadruple glazed IGUs. Simplified calculation formulas for the maximum thermal deformation of PIB in the X and Y directions under different temperature conditions were obtained, taking a new concept "cavity-to-pane ratio" into consideration. Finally, the relationship between the PIB's temperatureinduced deformation and its probability was proposed. The results show that the IGUs in Beijing suffer more than 22 % of their time in harsh service conditions where the difference between indoor and outdoor temperatures exceeds 20 degrees C. For DIGUs, the maximum temperature-induced deformations of the PIB in X (along the short side of the panel) and Y (along the long side of the panel) directions are 0.142 and 0.214 mm, respectively, corresponding to shear strains of 28.4 % and 42.8 % for the PIB with a thickness of only 0.5 mm. For TIGUs, the maximum deformations increase to 0.159 and 0.239 mm, corresponding to shear strains of 31.8 % and 47.8 %. For QIGUs and the other multi-glazed IGUs, these values can increase to 36.8 % and 55.4 % or more. The methodology proposed in this paper aims to lay the groundwork for further addressing premature failure issues and optimizing edge bond constructions of multi-glazed IGUs.

Precise and rapid calculation of triple-glazed insulating glass units (TIGUs) under uniform loads is crucial for the wind-resistant design and safety assessments of glass curtain wall systems (GCWS). However, available empirical data and numerical simulations are inadequate in accurately evaluating the mechanical behavior of this material. This paper presented an experimental and numerical study on the load-bearing performance of TIGUs, focusing on the equivalent thickness and load-sharing ratio calculation. Three pieces of TIGUs and five pieces of Polyvinyl Butyral (PVB)-laminated TIGUs were used in the loading tests. The major factors varied in the investigation include rectangular dimensions, glass pane thicknesses, and inner and outer airspace thicknesses. Two finite element (FE) models were built based on different methods. The applicability, accuracy, and computational efficiency of the models above were compared. Based on the conceptual and FE parametric analysis, the combined coefficient formula applicable to the calculation of equivalent thickness of PVB-laminated glass was proposed by surface fitting, and the load sharing ratio with respect to changes in the inner and outer airspace thicknesses was investigated. Finally, a simplified calculation method based on airspace coefficients, considering the effects of outer and inner airspace thicknesses, aspect ratio, and area, was proposed, which has superior applicability for precise and rapid evaluation of both TIGUs and PVB-laminated TIGUs commonly used in practical engineering, as the improvements to the stiffness distribution method adopted by the ASTM E1300.

This paper reports a comprehensive numerical investigation into the cross-section behavior and resistances of stainless steel lipped channel columns under axis compression. To obtain the influence of strain hardening index n and nominal yield stress σ0.2 on the design DSM compression resistance for a stainless steel lipped channel cross section, numerical parametric study has been firstly performed. It indicates that the strain hardening exponent n has a strong effect on the DSM strength prediction of stainless steel lipped channel columns, but nominal yield stress σ0.2 has a limited effect on the DSM curve due to it already included in the DSM. A DSM model was proposed that could take into account the strain hardening exponent n and different buckling modes, and a range of numerical parametric study was conducted. Based on the proposed DSM model, a set of DSM equations was proposed for stainless steel lipped channel column. The strength predictions formula is suitable for different types of stainless steel materials, and only the corresponding strain hardening coefficient n needs to be selected according to the stainless steel material. The comparison between the test results and design predictions indicates that the proposed equations are able to capture the nominal axial strength of the stainless steel lipped channel column

Currently, there is no detailed approach for designing cold-formed stainless steel lipped channel columns which fail by an interaction between distortional and global buckling. In this paper, the structural behavior of cold-formed stainless steel lipped channel columns that fail in distortional-global interactive buckling is presented. Finite element (FE) models were developed to simulate the members under axial compression. The results obtained from the finite element analysis (FEA) were compared with the test results in terms of failure modes, strengths and load–deformation curves. After successful verification, a comprehensive numerical investigation was undertaken to provide benchmark data for the assessment the nominal strengths predicted by using the current specifications (based on standards from AISI and AS/NZS) and the design equations proposed by Lecce and Rasmussen. The distortional buckling equation in the AISI code leads to overestimation of predicted resistances, while Lecce and Rasmussen’s formula provides conservative predicted resistances for stainless steel lipped channel columns. The AS/NZS code provides a relatively accurate prediction of the strengths. Finally, a design method for stainless steel lipped channel columns is proposed, which provides considerably more accurate predictions. The proposed Direct strength method (DSM) equation has been proven to accurately predict the ultimate capacities of stainless steel lipped channel columns in compression.