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Curtain wall systems made of an aluminum frame and infilled with glass panes are extensively used in present day high-rise buildings. The vertical members of the aluminum frame, known as mullions, are complex-shaped and are primarily subjected to bending action when the curtain wall panels are exposed to wind pressure or suction loading. This paper investigates the section moment capacity of 6063-T6 aluminum alloy mullion sections subjected to wind actions using a numerical study. An experimental study conducted to determine the section moment capacity of the mullions is summarized in this paper. The results from an experimental study on the mechanical properties of 6063-T6 aluminum alloy mullions are then presented including a suitable stress–strain model. Finite element models were developed to determine the section moment capacities of tested mullion sections, and the details of the finite element modeling procedure and the results are presented in this paper. The developed models included mullions used in the structural and captive glazing systems subjected to both wind pressure and suction loading and were validated using the available test results. Finite element analysis (FEA) results were compared with the predictions from three design methods, the limiting stress method (LSM), the direct strength method (DSM), and the total moment capacity approach (TMCA), based on which the most suitable design method is recommended

Thin-walled aluminium mullions are the vertical framing members of the façade systems used in buildings. This article investigates the buckling behaviour of these complex-shaped aluminium mullions. For this purpose, the aluminium mullion sections were simplified into elements of varying thickness and modelled using CUFSM finite strip analysis programme. Elastic buckling analyses were performed with and without considering the availability of glass panel restraints for both negative and positive wind actions, and the results are presented in this article. The effect of providing return flanges to enable a good connectivity between the male and female mullions was also evaluated. The lateral restraints provided by glass panels were simulated using the spring stiffness option available in CUFSM, and the analyses were performed for spring stiffness values in the range of 0–1 N/mm/mm. The applicability of the buckling analysis results to the design of aluminium mullions was then evaluated using the direct strength method. For this purpose, the section moment capacities of mullions were determined from finite element analyses and compared with the direct strength method predictions using the CUFSM buckling analysis results. This comparison showed that direct strength method–based design can be adopted for the complex-shaped aluminium mullions provided their elastic buckling capacities are available. Overall, this study has provided good understanding of the buckling behaviour of mullion sections under both positive and negative wind actions and has proposed the use of direct strength method for the design of aluminium mullion sections.

Load bearing Light Gauge Steel Frame (LSF) wall system is a cold-formed steel structure made of cold-formed steel studs and lined on both sides by gypsum plasterboards. In recent times its use and demand in the building industry has significantly increased due to their advantages such as light weight, acoustic performance, aesthetic quality of finished wall, ease of fabrication and rapid constructability. Fire Resistant Rating (FRR) of these walls is given more attention due to the increasing number and severity of fire related accidents in residential buildings that have caused significant loss of lives and properties. LSF walls are commonly made of conventional lipped channel section studs lined with fire resistant gypsum plasterboards on both sides. Recently, greater attention has been given to innovative cold-formed steel sections such as hollow flange sections due to their improved structural efficiency. The reliance on expensive and time consuming full scale fire tests, and the complexity involved in predicting the fire performance of LSF wall studs due to their thin-walled nature and their exposure to non-uniform temperature distributions in fire on one side, have been the main barriers in using different cold-formed steel stud sections in LSF wall systems. This research overcomes this and proposes the new hollow flange section studs as vertical load bearing elements in LSF wall systems based on a thorough investigation into their fire (structural and thermal) performance using full scale fire tests and extensive numerical studies. Test wall frames made of hollow flange section studs were lined with fire resistant gypsum plasterboards on both sides, and were subjected to increasing temperatures as given by the standard fire curve in AS 1530.4 (SA, 2005) on one side. Both uninsulated and cavity insulated walls were tested with varying load ratios from 0.2 to 0.6. LiteSteel Beam (LSB), a welded hollow flange section, which was available in the industry was used