Tensegrity Tower Rises Behind Hudson Hall

May 8, 2017

Engineering recreates art to offer a hands-on opportunity for learning about engineering analysis, synergy and integrity

A tower made of tubes that don’t touch one another may not seem like it should be able stand…but it can. The principles that make such a structure possible involve certain geometries and pre-tensioned cords connecting the tubes. Last Friday, April 28, a group of Duke Engineering freshmen and sophomores demonstrated this principle to be true.

As the apex of a new first-year design course in Civil Engineering, EGR190: Engineering the Planet, students created a Tensegrity Tower. Discovered by the artist Kenneth Snelson in 1948, tensegrities are defined by islands of compression (the tubes) within a sea of tension (the cords). By balancing the push and pull of these elemental components, the system achieves a stable form in which integrity is derived from internal tension. The system relies on every component and is more efficient than any system made of tubes alone or cords alone.

Emboldened from studying tensegrity in small scale models in the classroom, students gathered on the lawn between the Hudson Annex and the Levine Science Research Center to attempt a replica of Kenneth Snelson’s sculpture Needle Tower.  The class persevered through setbacks that only hardened their resolve, and triumphed in creating a 30 foot tower that was allowed to stand through the evening. The experience provided an first-hand experience in resilience engineering—the adaptability of systems to respond to extreme and unforeseen circumstances.

The project was hatched by Henri Gavin, professor of civil and environmental engineering, in collaboration with the class’s instructor David Schaad, professor of the practice of civil and environmental engineering.

Professor Gavin provided many insights into his choice of a final project:

 

“There is a lot to learn from building replicas of Kenneth Snelson's sculptures. They were discovered through art, not as a result of mathematical analysis. But they do offer interesting and hands-on opportunities to study math. Tensegrity concepts have been used to explain muscular-skeletal systems and the molecular dynamics of DNA and cell membranes.

Tensegrity requires 3D thinking. It does not exist in 2D (on flat pieces of paper) and even 3D computer graphics are not a substitute for building and holding these systems. The simple existence of the unique stable geometry that we see here today contradicts some concepts of system equilibrium as they are commonly taught in undergraduate engineering curricula.

As in many design enterprises, the difference between success and failure comes down to the details. In the case of tensegrity systems, experiencing how they are built by securing cables and tensioning cords by hand, every student truly feels how the system finds its equilibrium. The details of how it is assembled reveals the mechanics of how it works.

This project provides opportunities for learning about art history, the ethics of attribution, synergetics, assertiveness, teamwork, 3D thinking, mathematics, engineering analysis, and the simple pleasure of using tools to create something aesthetic with your own hands and sharing it with others. In the spirit of full disclosure, since we had never done this before, we didn't want to over-reach. This year our tensegrity is only 30 feet tall.  We are thrilled that it worked, we all learned a lot, and we are confident we can beat this height next year!”