Form Finding Flashback: Basento Viaduct

It is unclear where the unusual shape of the Basento Viaduct (Potenza, Italy) was derived.  Some even say the thin shell concrete pedestrian bridge is shaped like the headdresses of nuns in Federico Fellini’s Italian films [1].  Regardless, the Basento Viaduct is an example of a structure designed using early form finding techniques.

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Similarity in shape between the Basento Viaduct (left) and nun’s headdress (right)      [Photo Credit [1], [2]]
Today, we rely heavily on the use of computational methods for the form finding of thin shell structures. Yet, we see existing shell structures around the world that were designed and realized before engineers had numerical technology.  Who were these extraordinary engineers and how did they generate these unique forms?

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Ash wood – catastrophe or opportunity for creativity?

Since 2002, the emerald ash bore beetle, Agrilus planipennis, has destroyed more than 20 million ash trees in the US, with only 30% of the waste timber recycled into low-end products such as mulch and firewood. High value uses could turn this “waste” material into a valuable resource and an economic opportunity, especially considering that, before the widespread development of plastics, aluminum, and carbon fiber, the high tensile strength of ash wood was optimal for fabrication and use in the form of vehicle undercarriages, industrial infrastructure, and sporting goods. The ash bore beetle only established itself in New Jersey, a state with 24.7 million imperiled ash trees, in Spring 2014. The movement of ash wood is currently under federal and state quarantine.

In Fall 2015, Joe Scanlan (Director of the Visual Arts Program, Lewis Center of the Arts) and Sigrid Adriaenssens ran the course CEE418/VIS418 Extraordinary Processes to adopt new ways of thinking about and finding novel uses for local infested ash wood as a catastrophically available material.

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The MEDIA STUDIES exhibit, Lucas Gallery, Lewis Center for the Arts, Princeton Universy, features  sculptures crafted from ash wood by our students (from January 12 through February 5, 2016). These artworks exploit ash’s exceptional strength and flexibility and are at the same time unusual and beautifully crafted.  

Author: Sigrid Adriaenssens
Images: Sigrid Adriaenssens, Tim Michiels, Victor Charpentier

Sagrada Familia: the structure sometimes misunderstood

Incomplete but already a UNESCO World Heritage Site, Gaudí’s Sagrada Família towers over the city of Barcelona. Over a century in the making, the cathedral is expected to finish in the next 10-20 years.

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The cathedral’s nave has a unique and breathtaking roof geometry accompanied by rows of treelike columns.
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A spectacular amount of light filters into the nave from above.

In the form finding world, we’re often familiar with Frei Otto and Heinz Isler’s hanging methods, in which inverting a hanging model in pure tension informed the designer of the structure’s final form, which takes pure compression. While Gaudí is also known for making hanging models, a common misconception is that he embraced his hanging models as a way of determining the shape of his structures.

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Form exploration of shells in seismic areas

News broadcasts showing images of collapsed buildings, ravaged roads and torn-apart cities regularly remind us about the destructive power of earthquakes. While decades of research have greatly improved the understanding of these cataclysmic events, building professionals and researchers continuously try to adapt and employ the most sophisticated numerical methods to improve the behavior of buildings during a seismic event in order to safeguard their occupants.

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Las Manantiales Restaurant in Mexico City, a concrete shell designed by Félix Candela that behaved excellently during the 1985 Mexico City earthquake. (Image courtesy Félix and Dorothy Candela Archive, Princeton University)

Researchers at the Form-Finding Lab of Princeton University ( are exploring the design of elegant and expressive structures that can safely be employed in seismic areas. They focus on shell structures, which are very thin, curved and typically large span structures made out of wide range of materials going from steel and glass, to concrete and even bricks or mud.

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Welcome to the Form Finding Lab’s blog!

Under the direction of Prof. Sigrid Adriaenssens, we are a group based at Princeton University dedicated to studying the relationship between form and efficiency for the sustainability of future structures.

This blog serves to share ideas and news from members of the group. Feel free to take a look around!

About the Form Finding Lab

By 2050, 70% of the world’s population will live in cities. Structural engineers envision, design and construct the bridges and long-span buildings those city dwellers daily depend upon daily. The construction industry is one of most resource-intensive sectors, and yet our urban infrastructure continues to be built in the massive tradition in which strength is pursued through material mass. In contrast, the research at the Form Finding Lab focuses on structural systems that derive their strength from their curved shape, dictated by the flow of forces. As a result, these structures can be extremely thin, cost-effective, and less and CO2 intensive, all while reducing and, arguably conveying an esthetic quality.

Master builders throughout history have made significant strides in exploiting forms to enclose three-dimensional (3D) spaces, to provide shelter and protection (e.g. the Pantheon dome, Rome, Italy, 126 AD), or to bridge two-dimensional (2D) voids, such as water and roadways (e.g. the footbridges by Robert Maillart, Toss, Switzerland, 1932). In absence of numerical prediction methods, they resorted to trial and error construction practices or structural theory to establish a good enough structural form (see figure 1).



Evolution of structural form – weight versus year

Today, structural engineers are often excluded from the initial building or bridge design process and only appear in the picture only once when the form has been fixed. Pier Luigi Nervi, structural engineer and designer of the exquisite Little Sports Palace (Rome, Italy, 1958), stated: “Resistance due to form, although the most efficient and the most common type of resistance to be found in nature, has not yet built in our minds those subconscious intuitions which are the basis for our structural schemes and realizations” [1]. I place our scholarship at the Form Finding Lab in this force-modeled form tradition by pioneering novel numerical form finding approaches and unique structural forms. The forms we develop at the Form Finding Lab (eg.15, 16 and 17) are substantially lighter than their predecessors and contemporaries.

[1]            P. Nervi, Costruire Correttamente, Milan: Ulrico Hoepli, 1955.

Author: Sigrid Adriaenssens