Scottsdale, AZ, USA

FTL in collaboration with Pei Cobb Freed & Partners (Architect for the Campus Buildings) designed the sculptural tensile structure as a center piece for the overall development of ASU, providing a shaded center courtyard with 4 plazas for cafes, restaurants and social interaction. It serves as a landmark structure in the area to attract visitors. The PTFE glass fabric structure is approximately 50,000 sq ft of area and opened in May 2009.

FORCES & LOAD DISTRIBUTION

MATERIALITYTeflon-coated fiberglass (PTFE)

Its durability and tolerance against extreme weather conditions enhances its mechanical strength and allows maximum flexibility for curvy structures.

steel columns and cables

Galvanized steel A-frame columns acting as masts can withstand the tension forces through the connection with steel cables.

TENSION FORCES

CABLESTension forces from the cables are transferred from the top to the base in a wide spread direction. This ensures a larger base surface area for better stability.

COMPRESSION FORCESSteel A-frames (masts) transfer load from the top to the ground.

DEAD LOADThe weight of the membrane, bale rings and banana trusses are transported onto the ground through the A-frame columns.

environmental LOADThe whole structure can withstand the rain with the integration of drainage in the bale rings, preventing ponding of water in the fabric.

Wind load is also tackled with the strong connections of the fabric, where it can withstand 650 pounds of force per square inch.

MODELLING PROCESS

The initial model shows the exploration of materials and technique of construction. The fabric used is unsuitable as it lacks flexibility while the steel wire ‘banana’ trusses shows imperfection in workmanship.

Stretchable fabric sewn onto banana trusses and steel framing to ensure it is intact and maintain its shape.

Improvised model with A-frame column and base support (cork), banana trusses (steel wire inserted into plastic tubes) and framing of membrane structure.

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fabricStretchable PTFE membrane withstands tension with the support of cables, banana trusses and bale rings, which forms a series of conical shapes.

The overall tension forces acting on the structure is well spread with an equal amount of steel cable anchoring on all four sides of the membrane.

Pre-fabricated steel banana trusses are hung on the A-frame columns and act as connections of 4 pieces of PTFE membranes.

After attaching rings to the fabric, the structure is pulled into a pair of conical shapes with strings. It is then further tied into position.

Fabric stressesMaximum tension forces acting on the fabric are on the top and bottom rings, which shapes the conical structure.

WIND

Thin catenary cables inserted into fabric at the sides to maintain the curvature of the membrane structure.

ASU SKYSONG TENSILE STRUCTURE

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TENSION FORCESCOMPRESSION FORCES

SABD | Building Construction II | BLD 60703 | Project 2 Understanding Forces in Building Construction | Mr Edwin | Cherilyn Chia 0321986 | Lim Woo Leon 0322180 | Shreya Maria Wilson 0322173

Tension Intensity

Low TensionHigh Tension

ASU SKYSONG innovation centre

Concrete posts are built. A-frame columns and pre-fabricated ‘Banana’ trusses are constructed and supported by temporary cables.

After placing the bale rings in place with the support of cables, the customized PTFE membrane is connected to the top supporting cables and pulled upwards, forming its conical shape.

The PTFE membranes are installed in-place piece by piece with the sides joined to the Banana trusses, forming a full symmetrical structure.

STRUCTURAL ANALYSISFLAT TO CURVE

PTFE membrane is cut into quarters of circular shape and pulled into conical shapes with the bale ring and steel cables.

STEEL CABLE ANCHORING

The cables are anchored to the top of the A-frame and pulled to the banana structures and membrane to hang the elements and then pulled to the ground to maintain their positions.

CONSTRUCTION PROCESSBALE RING SUPPORT

Bale rings positioned at the top and bottom of each pair of A-frame columns allows the membrane to be tied into a series of conical shapes.

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