Complicated Cable Wall Highlights Nanning Wuxu International Airport
A nearly 65,000-square-foot glass cable wall curves along the entrance to China's Nanning Wuxu International Airport. The wall is curved at the top, and spans 656 feet along the building, sloping outward as it rises, reaching 98 feet at its highest point. The complex cable wall system presented steep challenges to the hardware supplier and design team.
An impressive curved and sloped glass cable wall system fronts the arrivals/departures hall of China's new 2 million-square foot Nanning Wuxu International Airport Terminal 2, designed by Kohn Pedersen Fox Associates. The dome-shaped hall serves as the central point of the expansive terminal and is designed to echo the shape of mechanical airplane wings, according to KPF officials. This aerodynamic aesthetic, highlighted in the building’s sweeping egg-shaped roof and canopy, continues throughout the glass façade.
Just as the roof and entrance canopy bend and bow, the glass wall follows suit. The nearly 65,000-square-foot glass cable wall curves along the length of the building, spanning 656 feet. Additionally, the wall slopes outward as it rises, and is rounded, or cambered, at the top, reaching 98 feet at its highest point, according to Shang Lingyan, engineer from Guangdong Kin Long Hardware Products Co., the curtain wall hardware manufacturer and supplier. The glass panels are insulating glass units that measure 118 by 59 inches.
The complex nature of the wall system presented notable engineering challenges for the façade team, according to Lingyan. “This design combines three technical difficulties: the curved glass wall, the [outwardlyfacing] design and the vertical cables,” she says. “The complication at this level requires an extraordinary design and perfect construction.”
In order to achieve this precision in the design and construction, the project team conducted extensive mechanical calculations and testing. This resulted in several improvements to the cable wall design, according to Kin Long officials.
The original design for the façade included a single vertical cable design with a custom hardware clamp that holds the glass, rather than drilling holes into the glass. However, the team discovered stress and load issues on the glass due to the various curves in the wall and the façade’s slope, Lingyan says.
“The single cable supporting glass façade had a large [deflection] when bearing the wind load,” she says. “The deflection of the glass wall was parabolic. The top of the façade is cambered, and the span for the cable system tapers from the middle to the sides. Because of this design, the deflection of the wall created high stress concentrations at the connection points, where the glass was clamped in the hardware.”
The project team modified the façade design to address the deflection and stress concerns, first by developing a double vertical cable support instead of the original single vertical cable design. “Compared with the original design of single vertical cable design, an extra number of cables were introduced to make a double vertical cable support to reduce and maintain uniformities of the stresses and balance the forces,” according to Lingyan.
The project features 64 sets of vertical stainless steel cables with diameters of 35 millimeters, 40mm or 45mm, depending on the position on the wall. The cables hang from a steel truss on the eaves of the main roof.
Kin Long officials note that a larger diameter single cable could have also provided a solution to the stress concerns. However, the team chose the double system with thinner cables to provide more transparency.
Adjustments were also made to the custom hardware clamps to further alleviate stress on the glass at the connection points. Kin Long designed a ball-joint connector that allows the system to better handle the deflection of the façade, according to officials.
Because the hardware clamps the glass, rather than attaching securing the glass with holes, the system is able to carry the deflection of both cables simultaneously, further reducing stress on the glass and providing additional safety for occupants, according to Kin Long officials.
The architect of record on the project was Beijing Institute of Architectural Design, and the general contractors was China Construction Eighth Construction Department Co., Guangxi branch. Dongguan Xinyi Glass Project Co. supplied the glass, and Wenzhou Yafei Aluminium Window Co., Nanning branch was the curtain wall subcontractor.