Glass curtain wall is one type of modern facade system and also a significant feature of modern buildings. The biggest feature it gives to buildings is the organic unity of architectural aesthetics, architectural functions, building energy conservation and architectural structure. Building facades present different tones at different angles, showing dynamic beauty with the changes of sunlight, moonlight and lights.
The stick-built (component-based) glass curtain wall is the most traditional structural form, the most widely used, and with reliable working performance. the issue of torsion and inclination in horizontal beams remains prevalent and recurring. The discovery of the torsion and inclination of beams is often after the project is put into use, and its rectification and repair is difficult, costly and inefficient. In this article, we will analyze the root causes of torsion and inclination in aluminum horizontal beams used in stick-built curtain walls under self-weight loads, based on current national codes and technical standards. Hopefully, it can provide a certain reference on how to avoid the occurrence of torsion and tilt of beams.
The division of panel sizes on the curtain wall façade is the most fundamental factor influencing the system’s self-weight. The larger the glass panels, the larger and heavier the supporting mullions and transoms must be. As the overall weight increases, the eccentric load imposed on the horizontal beams grows, raising the likelihood of torsion and inclination. Improper or overly large panel divisions not only increase design and construction complexity but also place greater demands on the beam’s torsional resistance capacity, making the system more prone to deformation.
According to Clause 6.2.6 of JGJ 102-2003 Technical Code for Glass Curtain Wall Engineering, when glass panels are installed eccentrically on a beam and generate significant torque, the torsional load-bearing capacity of the beam must be calculated. However, some designers fail to perform this verification in accordance with the code. As a result, once the curtain wall is installed, the combined effects of glass self-weight and wind loads can exacerbate beam torsion and inclination.
The establishment of construction sample sections serve not only as a visual preview of the curtain wall’s panel layout, color scheme, material specifications, and construction techniques, but also as a practical demonstration of the structural feasibility and installation workflow. Analyzing the sample sections helps validate theoretical data with on-site realities, so that we can ensure large-scale installation meets both structural safety and aesthetic expectations. However, in some projects, the establishment of sample sections are often neglected. As a result, beam torsion and inclination are only discovered after mass installation, but it is too late.
For the large glass panels , it is better to choose closed profiles or consider opening molds for customization so that the beams meet the structural requirements. In most cases, designers often choose from the existing models provided by aluminum manufacturers. The uniqueness of the project will cause the selected profiles to be unsuitable for the project under construction, increasing the risk of beam torsion and inclination.
According to Clause 5.5.2 of JGJ 102-2003 “Technical Code for Glass Curtain Wall Engineering”: The design of connectors of glass curtain wall including welds, bolts and rivets shall comply with the relevant provisions of the current national standards “Steel Structure Design Code GB50017” and “Technical Code for Steel Structure of High-rise Civil Buildings” JGJ99. There should be no less than 2 force-bearing bolts and rivets at the connection. When designers consider the connection between beams and columns, they often configure it according to this requirement. When the span of the beam is large and the glass panel is offset on the beam, using just two bolts can increase the risk of beam torsion and inclination.
During fabrication of curtain wall components, the precision requirements of component drawings are sometimes unclear, and quality inspection is not rigorous. For example, the accuracy of the opening diameter and the geometric scale deviation do not meet the requirements, which seriously affects the installation quality.
There are a certain number of outdated processing equipment in curtain wall construction. They have not been calibrated, repaired or updated for a long time, and their accuracy and efficiency have declined, which directly affects the processing quality.
In summary, the torsion and inclination of aluminum alloy beams in stick-built glass curtain walls is not an isolated incident, but the result of the combined action of multiple factors, covering multiple links such as design, material selection, construction, processing and inspection.
In order to effectively avoid the occurrence of such problems, it is necessary to strengthen the rationality of the grid design, strictly review the structural force calculation, strengthen the verification function of the construction sample section, and improve the processing accuracy and equipment guarantee capability at the beginning of the project.
Only by implementing each link in place can the safety, reliability and aesthetics of the curtain wall system be truly realized, and its due value can be played in modern buildings. It is hoped that the analysis in this article can provide useful reference for relevant engineering design and construction personnel.
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