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Feature article

Tensile installation meshes grace + strength

A project to provide an aesthetically pleasing safety solution for the atrium at Melbourne University’s new School of Design presented a number of challenges for tensile architectural solutions supplier Tensile Design & Construct.

Designed by John Wardle Architects, in collaboration with Boston based firm NADAAA, Melbourne University’s new School of Design houses the faculty of architecture, building and planning.  As well as a place of learning, the structure was conceived as a teaching tool in itself, featuring raw, exposed detailing that reveals the methodology behind the building’s construction.

A key element of the building is an open five-storey atrium, and, as Tensile Design & Construct Business Development Manager Peter Bottero explains, a solution was required to provide a safety barrier between all levels of the opening, while respecting its sight lines and air flow.

“A material was needed that had a large open area, was structurally strong enough to handle crowd loads but was flexible enough to work with the architectural language proposed by the architects. It needed to act as the infill between the buildings.”

Tensile Design & Construct was engaged to design, engineer, fabricate and install a stainless steel mesh screen and supporting stainless steel tubing. The product selected was a highly specialised mesh known as ‘Webnet’, made by Jakob Rope Systems of Switzerland, a 111 year old family business “that makes impeccable quality products.”

“The Webnet features remarkable wire fineness and 95% openness, both of which were key to creating a veil like structure capable of withstanding considerable force”, Bottero says.

“Each wire of the mesh is only 1.5mm in diameter and the aperture opening is 80mm. The mesh and tubes were designed and engineered by Tensile to take all pre-tension forces of the mesh and cables plus a 0.75kN crowd load as per AS 1170. Tensile has designed mesh barriers to also take the higher load case of 3kN under the code and even fall protection loads.”

Describing it as one of the most complex installations Tensile has attempted, Bottero says the project entailed over 1200 square metres of mesh, with key challenges primarily relating to the geometry of the structure.

“There are very few straight edges in the building; everything is on an angle. Also the tubular balustrade had over 750 unique components, with each needing to be created in 3D and bent in complex geometric patterns.”

“We also had to work through a multitude of connection details, many of which were one-offs due to the geometry. These all needed to be documented in 3D to ensure we had cables and mesh moving in the right direction.”

“With the installation taking place within an extremely confined space, and over 100 tradesmen needing to use the same area, it was certainly a tight program.”

The Webnet mesh was brought to site in several pieces and stitched together to achieve a single continuous piece of mesh for each side of the atrium. This enabled the large and complex shapes to be made and also made for a fast and easy installation. The final construction took four months to design, with installation occurring over two months, and was in fact completed more than three months ahead of schedule.

The final result appears to attest to the unique properties of the mesh.

“Webnet mesh behaves like a tensioned membrane, which is what made it ideal for the School of Design and the role it plays of stretching across the atrium walkways and balconies,” says Bottero. “The mesh laces to a series of 5 and 6 mm stainless steel cables that then anchor back to the slabs and other structural members of the building. The result is that any impact load is radiated across the whole mesh façade; each wire supports its mate, thereby reducing the cross-sectional area required by each wire.”

“The triangular shapes in the tube balustrade and the large timber seating and tables also act as part of the structural solution. In fact we dubbed it the ‘structural furniture’ during the project as it was the first time I have ever come across the need to understand how a table or chair would behave in a crowd load situation. The tubes, through their triangular shape, provide a larger fixing or surface area to resist force and the timber forms a kind of bracing in much the same way ply wood sheets do for a timber wall. All of this enabled a highly sophisticated and efficient structural solution.”

“Mesh performs beautifully, there is no other material that could provide for all of the architects’ needs and fit the complex geometry so easily. The mesh stretches, twists and folds between the various shapes and forms surrounding the atrium. It is a bit like a veil, but a veil that can take a football team running at it. Like most of our cable structures, the end result appears effortless. However this simplicity hides a multitude of details and complexities that are lost on most people who look at it. That is why we love what we do.”

“The lightweight but extremely strong construction created for the School of Design is only available through tensile objects. We are seeing this embraced more in the building industry but there is still room to grow. We certainly have not mined the full potential of Webnet mesh as yet.”