Revisiting a senior thesis: smart structures

Imagine having a lazy Sunday and laying out in the sun, but never having to get up and move your shade umbrella to a more optimal place throughout the day. This kind of technology is possible when structures and technology combine to make “smart” structures. Your umbrella could be a structure that senses the location of the sun through the solar panels on its covering, and depending on the amount of sunlight available, create optimal umbrella structure shapes for you.

How can this be done?

“Smart structures” are in fact highly possible. For my senior thesis at Princeton, I studied these adaptive sun shading structures, and my built model was composed of a pre-stretched dielectric elastomer adhered to an inextensible compliant frame. At a small scale, these built flexible models could furl and unfurl predictably. However, these built models were very small and labor intensive. What if there was a way to numerically compute possible “smart” structure shapes to more quickly iterate through different designs? In addition to verifying the built flexible models, I strove to understand if a computational method called dynamic relaxation could be employed for the analysis of dielectric elastomer minimum energy structures (DEMES).

siu1 — Photos of the DEMES structure studied

So can dynamic relaxation be employed for the analysis of DEMES?

The short answer is yes, it seems like it can.

Dynamic relaxation, a common structural form finding method, was chosen as a numerical simulation technique to simulate the curling action the DEMES. Dynamic Relaxation introduces a fictitious inertia and damping terms into the equations of motion, formulating a static system as the equilibrium state for a group of damped vibrations.

DEMES equilibrium shape obtained with the dynamic relaxation model

Comparing computed shapes to the physically modeled stretched elastomer structures, there was a noted correlation between equilibrium angle and applied voltage for a biaxial stretch when using a modified Dynamic Relaxation algorithm with bending and clustered elements. Overall, while I found that a numerically modified structure is influenced by material uncertainties approximated input values, the Dynamic Relaxation technique was found capable of predicting the shapes and elastic energy of DEMES.

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Interviews

What I am thinking: Structural designer Jane Wernick

Jane Wernick is a British Engineer who has distinguished herself in the field of structural engineering. She has taught at Harvard University and has been the Chair of the Diversity Task Force of the Construction Industry Council, in addition to managing Ove Arup and Partner’s Los Angeles office from 1986 to 1988. In 1998 she founded Jane Werwick Associates Ltd., a superb engineering design consultancy which has worked on countless projects across the United States and Europe. I talked to Jane at the occasion of the Structured Lineages: Learning from Japanese Structural Design event, held earlier this year at MOMA.

Sigrid Adriaenssens: You have worked with world-renowned architects, what is the value for you of working in a design team versus solo engineering?

Jane Wernick: I have only ever worked as part of a team. I very much enjoy the process of trying to work out and understand the aspirations of the client, architect and other consultants, and then trying to find structural solutions that support or even enhance those aspirations.

What objectives do you set for yourself when designing a structure? How would a trained audience recognize a structure designed by you?

I am keen to propose solutions that give delight, that are buildable and that give good value. As well as designing structures that are strong enough, stiff enough, durable etc. it is also important that, as engineers we appreciate what the structural elements will look like. For example, I think that a circular hollow section is likely to look much larger and heavier than a fabricated section with sharp corners. The triangular cross section is one of my favourites. This is what we used for the pylons of the Xstrata Treetop Walkway at Kew Gardens. Because we used weathering steel (because it didn’t need to be painted with an ‘un-natural’ colour) we couldn’t use rolled sections. And a tapered triangular cross-section was the most efficient we could use. It also looked more slender than the equivalent circular section would have appeared.

southwalkway — South Elevation Xstrata Treetop Walkway showing the pylons

londontown — Close-up Xstrata Treetop Walkway (Image credit LondonTown.com)

You once said “structural analysis is not a precise science, but difficult statistically; it is chaotic, and it is part craft” in the context of your work with the Fiat Team. This statement might seem upsetting to engineering students. Could you elaborate on this?

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Engagement

IASS 2016: Out and about in Tokyo

Last week I had the opportunity to travel to Tokyo for the 2016 IASS Symposium, as one of the award recipients for the IASS design competition for an alternative New National Stadium. While I spent most of my time at the conference sessions, I still got to see many incredible structures while on a tour organized by IASS. Here are some highlights:

The Prada store by Herzog & de Meuron and Yakenaka Corporation features a lattice of H-sections that serves as both the lateral structural system and as the façade.

While on the tour, we got to see the Yoyogi Indoor Stadiums built for the 1964 Olympic Games. This was a very special visit, not because the 2020 Tokyo Olympic facilities were a major talking point at the conference, but because chief engineer Mamoru Kawaguchi was there to explain the project to us. At the time, Dr. Kawaguchi worked at Yoshikatsu Tsuboi’s firm, which designed the stadiums together with architect Kenzo Tange.

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Miscellaneous

Adaptive Reuse: How can we make old buildings more sustainable?

One of the most important tasks engineers face today is the design of sustainable structures. Through form finding, use of efficient and/or local materials, and external systems, a plethora of new environmentally responsible buildings exist today. These advanced structures seem to be the answer to reducing the building sector’s staggering carbon emissions, but what about old, historic architecture? What role do these buildings play in our sustainable future?

Tearing down all structures that aren’t explicitly sustainable isn’t necessarily best for the environment, as additional energy is required for demolition as well as construction of a replacement structure. Furthermore, these buildings also hold cultural and historical relevance, acting as roots that tie us to the people and virtues who came before. Old post offices, banks, schools, office buildings, and retail locations may never find their place in history textbooks, but their vernacular styles, as well as the people and events that populated their interiors, make them worthy of preservation. Sustainable design isn’t restricted to the environment; social and cultural sustainability should also be of our concern.

In order to understand how to best include these buildings within our sustainable agenda, it is important to look at their current environmental impact compared to most infrastructure found today. According to the National Institute of Building Sciences’ Whole Building Design Guide, “historic buildings are inherently sustainable.” Adaptive reuse of old structures not only ensures the maximum use of material lifespans but also reduces waste. These claims are corroborated by life cycle analysis (LCA) tests, demonstrating that “reusing older buildings result in immediate and lasting environmental benefits.”

Though these structures may not be as energy efficient as new high-tech ones, LCAs found that performance is not overwhelmingly compromised, as many existing buildings already have sustainable features. With the lack of significant climate control technology at the time of their construction, the form and materials of many old buildings were inherently efficient, trapping heat in the winter and releasing heat in the summer. Features include thick walls, shutters, overhangs, awnings, and high ceilings for air circulation and light admittance. Therefore, these sustainable features will be retained when rehabilitating and renovating them for contemporary use. Thus, with their waste reducing benefits, as well as their current level of performance, the best way to make old buildings sustainable is to use them.