Commissioned for TIAA’s new headquarters in Frisco, Texas, Bluebonnet is a large-scale public artwork by SOFTlab inspired by the Texas state flower. The piece consists of 570 custom laser-cut aluminum tubes, each bent at varying angles and lengths to create a sense of movement within a radial array. Integrated LED lighting reflects off cut “petal” surfaces inside each tube, generating a layered lighting effect that evokes wind moving through a field of flowers. The result is a dynamic landmark that shifts between structural object and atmospheric presence.
While each of the 570 tubes creating the visible art is unique, the primary structural system consists of a doubly-symmetric and vertically tapering steel plate tower core with an identical connection detail for every unique tube. The steel tower core was designed to be fully erected in the field without the use of field welding or heavy equipment. The tower vertical plates are comprised of multiple discrete plates stitch bolted together to create a thicker, stiffer section.
Horizontal ring plates bolt to the verticals via angle brackets to complete the ring tower. Finally, a toothed plate bolts to the horizontal plate elements to provide the attachment points for the tubes.
The symmetry and linear taper of the tower core allow for repetition in the plate elements that proportionally reduce in scale up the height resulting in a tower core with more mass and stiffness at the base where it is most effective.
Code-derived wind loads determine an average pressure value distributed over the full structure which was used to design of the global system including the steel plate tower core, reinforced pedestal foundation, and anchorage. However, code-derived wind loads fail to capture the effects of wind shielding, vortex shedding, and localized pressure spikes that have significant impacts on components that comprise the full structure.
Virtual wind tunnel studies were used to evaluate the unique behavior of wind flow on the delicate aluminum tubes to ensure sufficient stiffness and strength for pressures above the code requirements. Positive pressure spikes at tubes high in the system and tubes lacking shielding as well as negative pressure spikes (suction) at the leeward and sides of the sculpture were evaluated directly on the structural analysis model. This allowed each unique member to be designed for the precisely anticipated localized effects not possible with traditional engineering approaches.
Once the member behavior and wind loading were thoroughly investigated, a solid element FE analysis was performed on the component connection assembly between the tubes and supporting steel tower. Specific attention was made to local stresses and deformations in the thin-walled, delicate aluminum tubes. The top level assembly was evaluated to capture the longest cantilevered tube subjected to the highest wind-tunnel derived pressure.
Bluebonnet showcases the power of digital design tools to create and rapidly evaluate seemingly complex forms from relatively straightforward components. CRAFT is dedicated to furthering our technical capacities to better support collaborators like SOFTlab who are striving to push the boundaries of what they are capable of creating.
Project Team
Artist, Fabricator: SOFTlab
