“Postcards From …” Series: Summer 2016

Throughout the summer, friends of the Form Finding Lab have been sending postcards from the places they have visited. The postcards are also featured on our Facebook page. For this special summer post, we’ve compiled the postcards for all to enjoy!

For the next 2 weeks we are on vacation. Stay tuned for more of our exciting posts in September!

May 2016
May 2016
May 2016
June 2016
June 2016
July 2016
July 2016
July 2016
July 2016
July 2016
July 2016
July 2016
July 2016
July 2016
August 2016
August 2016

August 2016

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August 2016

Author: Victor Charpentier


In the spirit of the Olympic Games: the “Carioca Wave” Freeform of Rio de Janeiro


The Carioca Wave was completed in 2013 in Rio de Janeiro, not far from the 2016 Olympic Village site. We first discussed this structure in our interview with Knippers Helbig. In this post we observe architect Nir Sivan‘s design process for designing this elegant structure.

Creating the “Carioca Wave” project in Rio

When Nir Sivan got the opportunity to build a freeform steel/glass canopy roof as a welcoming entrance area to “CasaShopping,” South America’s biggest design center, he was thrilled and knew that whatever he designed, it had to be and behave as a part of the “marvelous city,” as Rio is often nicknamed.

Nir Sivan started working on the master plan in his office in Rome, but the actual shape of the project was only designed when he came to Rio. The inspiration came while he was sitting on one of the many famous beaches with a local cold drink. He remembers drawing in his sketchbook – 5 or 6 simple lines, but they captured it all:
 the calm; the movement; the sound, the “Carioca,” as locals from Rio area are called.

He created a shape of a single yet geometrically complex surface of the double curvature. The surface starts at the upper floor above a blue colored water pool, then rises up curving, growing forward, twisting to the other side, and finally dropping down to a lower floor, splashing into a white colored pool. Around it you will find water, sand, Portuguese paving, and other elements to merges the project with the local language.

Inspired by its context, the project was driven artistically and emotionally, and developed architecturally, adding both value and function to its surroundings.

“Sculpting architecture”

The design approach included sculpture and design methods that were further developed using automotive industry tools and advanced parametric instruments to ensure tight control of the very particular geometry. Nir Sivan developed this unique process involving automotive industry, believing it gave him complete freedom to create while maintaining coherence with concept, structure, and form.

Putting things together

Nir Sivan’s projects often require cutting-edge technologies as well as advanced fabrication and installation techniques. The Carioca Wave gridshell uses over 110 tons of carbon steel (fabricated in Czech republic), including 36mm-thick double-curved tubes, 765 different beams, and almost 300 different laser-cut shaped nodes, creating 503 varied triangles accommodated by glass panels that weigh 45 tons (fabricated in Japan) – all shipped to be installed in Brazil.

The partially-clad Carioca Wave gridshell is temporarily supported during construction.

As he often does in similar projects, Nir Sivan created a design-build group: he teamed up with engineers Knippers Helbig (Germany) as right-hand partners and construction company Seele (Austria HQ) for fabrication and installation. By doing so, he was involved in all aspects and processes of the development, assuring that his design intentions were maintained and that the final results corresponded to his expectations. The client was free from any responsibility of coordinating this international team.

Architecture precedent

The structural frame of the Carioca Wave canopy is a self-supporting gridshell, requiring neither columns nor lateral supports. Nir Sivan sought to combine this self-supporting system with wide cantilevers to push technology to its limits. As Nir Sivan was informed during its design, the Carioca Wave is the first freeform architecture in South American history.

Nir Sivan believes that people appreciate design and recognize the “added value” of implementing new techniques and technologies. He looks forward to sculpting more architecture worldwide.

Close-up of the gridshell support, lit at night

Image Courtesy Nir Sivan Architects

You can read more about Knippers Helbig Advanced Engineering in our previous post

What I am thinking: from Stuttgart to Rio 2016 SBP’s stadium designer Knut Stockhusen


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Rio de Janeiro, with Stadium Maracanã in the distance. © Marcus Bredt.

The world has tuned in to the Olympic Games in Rio de Janeiro to witness the highest caliber of athletics. However, unbeknownst to most spectators, this is also an occasion to see first-rate structural engineering: A lot of the action will be taking place against a backdrop of stadia and venues made possible by the work of schlaich bergermann partner (sbp).

Engineer Knut Stockhusen is a partner and managing director at sbp, and was paramount in establishing sbp’s presence in Brazil. In April, he came to visit Princeton to give a lecture and workshop on deployable roof structures, and I was lucky enough to sit down with him for a conversation.

Before talking about Brazil, I first wanted to hear more about schlaich bergermann partner.

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Rio de Janeiro Olympic Live Site (2016).© Dhani Borges

Olek Niewiarowski: You’re always traveling and working around the world, but you’re based in Stuttgart, Germany. How is that like?

Knut Stockhusen: Our HQ is in Stuttgart, that’s where a lot of our activities are coordinated. But we have five other offices: Berlin, where Mike Schlaich is professor, New York, Sao Paulo, Shanghai, and we opened an office in Paris just this year. We noticed over the last few years that while it’s good to have one “base camp”, we still need several locations where we can work and live. We can’t travel all the time, and it is paramount to adjust to the local culture and the way of doing things.

What is special about Stuttgart?

There are many things special about Stuttgart. Stuttgart is the place where a lot of technology and engineering got established. In our field, Fritz Leonhardt started his incredible career in Stuttgart. He had a very progressive approach and revolutionized the whole engineering world with principles that are still commonly used all around the world. For example, look at the Stuttgart Television Tower: It was the first of its kind in the world and it got “exported” everywhere. This environment was a very powerful base for new stars to rise, such as Jörg Schlaich. He started to develop new approaches to cable structure design for bridges and for other tensile structures. With the solution for the Olympic stadium in Munich, he not only developed, but also revolutionized that field. The influence of Jörg Schlaich on engineers in Stuttgart is quite visible. Of course, everyone develops their own approach, but it is very interesting to have several important players in such proximity. Sometimes it leads to competition, but in most cases it is just nice to be enveloped by such excellence.

It sounds like the “DNA” of the firm crystallized early with all these lightweight structures. On a day to day basis, how do you keep the SBP style alive?

In a way, it’s a certain engineering philosophy that we pursue. Its seeds came from Jörg Schlaich and Rudolf Bergermann, in the constant pursuit of an incredible variety of international projects and technologies, where the limits of feasibility were pushed constantly.

Those values were successfully inherited, enhanced and carried into a new era by the next generation of partners and the whole team. The will to explore the unexplored, to venture into new fields, to never hesitate, and to keep on developing, evolving and sometimes revolutionizing in a structural sense. That is something we live by on a day to day basis.

Can you give an example of how you live by this philosophy?

We are active in most of the fields of structural engineering. If you look at one of these, the field of stadium and large-span roof design, we have designed something like 50 stadiums around the world. Now if you compare the solutions, you will recognize that none looks like the other. Of course, every time we start a new project, we base our approach on what we learned before, but we yearn to develop something new. We try to find solutions that suit to the architectural layout, the environment of the city, and to the capabilities of the region. We try to form new creative teams, develop something that was never done before.

So maybe we can talk more about stadiums: What was your most challenging stadium project?

In terms of the combination of environment, cultural surroundings, and the technical capabilities of the region, the projects that we did in New Delhi were probably the most demanding. We designed stadiums for the 2010 Commonwealth Games and started our operations there in 2006. For the main stadium, the job was to develop a new spectator approach and roof structure. Since the existing tiers were in a state of conservation that was not so, let’s say, promising, we decided to do an independently-supported roof. Due to the setup there and the decisions taken by the authorities, that project really demanded a lot from our team, from myself, and the office. For example, they allowed the contractors to fabricate on site. So they first started to build fabrication plants on site, and the steel suppliers would just drop off the steel plates on site and the contractor would start to weld everything there.

We had to involve our fabrication experts to, for example, guide the contractor to build covered work areas to get out of the sunlight, because you have extreme heat and your steel distorts and all your lengths get messed up. It turned out well at the end of the day, but it was really challenging.


JNS Jawaharlal Nehrun Stadium (Delhi, India, 2010). The stadium features a classic SBP ring-cable system based on a spoke wheel. © Knut Stockhusen.

It sounds like you must be really aware of how things get done on the ground before you can even start designing?

Our approach is to design with excellence, perfection and uniqueness, but always considering the fact that someone is going to build what we’re designing.

We analyze the possible setup of the contractors, we consider their capabilities and who will actually do the work at the end of the day. We try to be involved in these projects from the first sketch to completion, in order to guide the client, who maybe has never done this before.  To achieve the best setup for fabrication and construction, we have experts in all fabrication issues who survey and guide fabrication. And in this particular case in India, we had to establish a full-time supervision team on site, which was not planned for in the beginning. They actually taught unskilled workers on site how to weld and then test the welds, in order to guarantee that the whole structure is capable of 50-year lifetime.

So when you talk about supervision, how does a contractor in India respond to that? Is that something they are used to, or was it a new thing for them?

The detailed involvement of a structural designer was an extremely new experience for them. And it is actually new at many projects. Our philosophy of not “letting go” of a project once the design is finished may create a certain friction in the beginning. However, in all the cases that we’ve been involved, it turned out to be a truly successful collaboration in which the site teams appreciated our input. You need time to get used to each other, and that demands a lot from both sides.

We are engineers who roam the world looking for beautiful projects. We cannot expect and we don’t want to expect that people get used to our culture. Maybe to our culture of building, the culture of construction, and certain safety standards, yes, but it is our duty to get used to the circumstances of a particular region and to rules of engagement.

This can be very exciting and at the same time very demanding, but it’s also rewarding because you get to know the culture, you get to know the people. Everyone in the company who gets to travel to sites establishes strong friendships that add to the success of schlaich bergermann partner.

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Stadium Maracanã (Rio de Janeiro, Brazil, 2013) © Marcus Bredt.

SBP’s Sao Paulo office opened before the 2014 World Cup. What was your role in that again?

We opened the office in 2007 and I almost moved there because I traveled every third week or so. Together with our Brazilian director Miriam Sayeg, who is crucial to the success of the establishment, I manage the South American activities. You need someone who is engaged in the local community and environment, especially in a country like Brazil, someone from Brazil who knows their way around in terms of communication and culture and networking.

Do you have a favorite stadium in Brazil? Is there one we should look out for during the Games?

Normally, the Olympics are held in one city – it’s called “Rio 2016” for a reason – so it becomes its own brand. The interesting thing about Rio 2016 is that some events will take place in other cities in some of the stadiums built for the World Cup, because they are there! For example, the Arena da Amazônia in Manaus will host soccer.

Which stadium do I find most interesting? From an emotional and personal point of view, I would say Maracanã Stadium. It’s the one that you dream of as a stadium designer (and a soccer fan) and it’s a spectacular project in a very spectacular environment.

Stadium Maracanã © Marcus Bredt.

But the Arena da Amazônia is also a very special project for me. It took a great deal of personal effort to engage in the environment and to realize that project in such a special and remote city. I believe the design is really incredible: it’s a very beautiful project – in a wonderful part of our planet.

Arena da Amazônia (Manaus, Brazil, 2014) © Marcus Bredt.

Everyone is worried about the rainforest and that is also very important for us, so it’s also interesting to mention that no tree had to be cut down to build the stadium. But in particular, no one would have taken notice of this region during these mega events if there wasn’t a venue there for certain games. So now, like in the World Cup, billions of people will look at that region and maybe start thinking.

For the people living there it is very important to be part of the whole show. That’s already a good reason for having the Arena da Amazonia in Manaus.

So does that tie into the social responsibility that sbp advertises? It sounds like you can make stadium building a sustainable venture.

Yes, in a way it is part of our philosophy that we try to reflect in the way we design. We design structures that can engage the local capabilities and work force to create jobs. On the other hand, the main motivation to work in the field of lightweight structures and intelligent structural systems is to try to avoid wasting resources. Sustainability is a very big term that everyone is talking about. What is really sustainable?

The material that is not used is the most sustainable material, hence we try to limit the use of natural resources as much as possible. By doing that, the beautiful lightness of our design becomes visible.

Not everyone has to love it, but in our eyes, the lightness and elegance of slenderness motivates us to come back day after day.

We were running out of time, but I still had two very important questions for Knut.

What question do you never get asked, but would like to be asked?

Ah yes, that is the most important question. The question would be, “Are you happy with what you do?” Yes, I’m very happy. We are happy with the work that we do; it’s a very profound work. There is also this sense of evolution and development that is the foundation of our great team. It inspires and keeps people in the office. They see that they can contribute and have a significant impact.

What is your advice to students interested in lightweight structures?

Call me.


Author: Olek Niewiarowski

All images courtesy of Schlaich Bergermann Partner.


A New Design for the Tokyo 2020 Olympic Stadium

Looking ahead, the next Olympic Games will be hosted by Tokyo in 2020. The initial Zaha Hadid design for the Tokyo National Stadium helped secure the city’s bid, but was quickly ditched due to its exorbitant cost.  After two international design competitions, Japan settled on the latticed green clad stadium by the Japanese architect Kengo Kuma.

This new stadium is far more subdued than Zaha Hadid’s and does not evoke the same awe as the National Gymnasium by Tange and Tsuboi Yoyogi.

To reflect upon and honor the structural prowess visualized in the sweeping roof lines of the Yoyogi Stadium, as well as to keep an open mind toward the future, the International Association for Shell and Spatial Structures (IASS) organized a conceptual design competition for a new national stadium in Tokyo, open to young designers under the age of 40.

The competition called for a “21st century spatial structure” on the site of the former National Olympic Stadium by Mitsuo Katayama. The competition jury, consisting of professor emeritus Hiroshi Ohmori (Nagoya University), architect Hiroshi Naito, engineer Knut Stockhusen (sbp), professor Ken’ichi Kawaguchi (University of Tokyo, Chair of the IASS2016), and engineer Bill Baker (SOM), considered the innovativeness of the concept system and the soundness of the structure.

I have the pleasure of presenting three design proposals developed and submitted by our graduate students. They all used form finding techniques in innovative ways to drive the geometries of their stadiums.

The Mountainous Gridshell entry by Mauricio Loyola and Olek Niewiarowski has been selected as one of five finalists by the competition jury, and they have been invited to present their design in September at the IASS Annual Symposium in Tokyo.

NEW LEAF STADIUM by Xiaoran Xu, Lu Lu, and Iwanicholas Cisneros (click to enlarge):


HANA STADIUM by Kaicong Wu, Hongshan Guo, and Isabel Morris (click to enlarge):


MOUNTAINOUS GRIDSHELL by Mauricio Loyola and Olek Niewiarowski (click to enlarge):


Author: Sigrid Adriaenssens


Our Summer Rammed Earth Experiments 2/3: Construction of swirling rammed earth wall

Before the large swirling structure in Forbes garden could be constructed, a set of tests walls were built to master the construction workflow. The tests walls will also be used to test a different set of erosion protection measures, as one of the goals of our research experiment is to assess the erosion resistance of rammed earth in New Jersey. The first test wall was built out of unstabilized earth with no erosion protection implemented for reference. The second wall was also unstabilized, but plants will be grown on top of this wall in the hope that their roots will slow down the erosion process, while their leafs protect the dirt from driving rain. The third test wall was stabilized on the outside with a 10% lime-earth mixture, which was applied only at the outer 3 cm. This technique is a traditional rammed earth construction technique originating in Spain and referred to as “calicascado” which can be freely translated as “lime shell”. The 4th and final test wall was built unstabilized earth once again again, but half of it was coated using a silicone spray, while the other half was coated with a lime wash. All of the test walls were built with a reusable plywood formwork on top of a blue stone slab..

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Scheme of the test walls
Rammed earth test walls. Both left walls are unstabilized, the wall still in the formwork was built using the calicascado technique.

After the successful completion of the test walls, we moved on to the much larger spiraling wall inside Forbes garden. As explained in the previous blogpost, the spiral consists of a lower bench area and a taller wall, separated by an opening. At its lowest point the bench is 40 centimeters high, and at its highest point it is 3 meters tall. Both rest on a blue stone foundation. Again, different erosion-protection measures were implemented. The bottom 15 cm of the entire wall was made out of a 25% lime- earth mixture, and placed on a water impermeable membrane to avoid capillary rise. The outside of the bench and most of the rest of the spiraling wall was stabilized using the calicascado technique after its promising results on the test walls. A great advantage of this technique is that it allows for a minimum volume of soil that needs to be stabilized with lime and thus requires less material transport. To compare the durability of the technique once again a section was left unprotected. Additionally, one section of the wall was entirely lime-stabilized using 6% lime as an extra test.

Lime-stabilized outer layer (“calicastrado”) waiting for infill dirt.

One of the goals of the project was to demonstrate that it is possible to break away from straight rammed earth walls and build elegant curving elements. This required the construction of curving formwork, which was assembled from standard wooden 2″x4″ elements and bendable plywood. To account for the huge outward thrust created by the compaction, horizontal support triangles were built from using the same wood. Additional horizontal pieces were screwed in between the supports to prevent bulging and cracking of the plywood.

(From Left to Right): formwork assembly, manual spreading of the earth, bendable plywood sheets being installed, pneumatic compaction of the soil

The actual ramming of the earth was done by coating the formwork with a 3-4 cm thick layer of lime stabilized earth (mixed on site), which was then filled with local Princeton soil from the Princeton University construction yard. This soiled had been screened through a 1 inch mesh and moisturized to the optimal water content of about 10%. The soil was lifted into the formwork using an excavator, after which it was spread by hand, and then compacted using pneumatic backfill tampers.

 (From Left to Right): Excavator filling the wooden framework with earth, Flattening the earth with tampers, Compressing the earth with pneumatic tampers

Subsequently, the formwork was disassembled and peeled away from the compacted earth. This is a fairly easy process thanks to the thrust exerted by the dirt. The majority of the lumber used for the formwork will be recycled and reused in a next construction project.

View onto the swirling wall

Finally, the top of the wall was covered with a water-resistant membrane and planking of untreated cedar wood.

We would like to thank Shana Weber (Princeton University, Office of Sustainability), Sean Gallagher and Brian Scelza (Princeton University, Facilities)  for their support for our project.

Author: Jacob Essig & Tim Michiels

Project By: Tim Michiels & Sigrid Adriaenssens

Construction team: Tim Michiels (project coordinator), Eric Teitelbaum (coordinator formwork construction), Amber Lin, Jacob Essig, Victor Charpentier, Sigrid Adriaenssens, Olek Niewiarowski, Princeton University Civil Construction: Steve, Paul and Mike.

A Delightfully Sweet Pavilion

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Close-up of the puzzle-key connection in the chocolate pavilion. (Image credit Axel Kilian)

On July 21st every year, we celebrate Belgian National Day and think about all the good things Belgium has to offer: Tintin, cycling, soccer, and– from a more gastronomical perspective– waffles and chocolate. This is an ideal time to reflect upon our chocolate design project from 2013.

A pavilion made out of chocolate must be a cocoa lover’s wildest dream. We teamed up with Prof. Axel Kilian (Princeton University) and the Belgian chocolate manufacturer Barry-Callebaut to discover chocolate’s structural properties and let them inform our methodology for finding the shape of such a pavilion.

The R&D branch at Barry-Callebaut developed a cocoa compound of sugar, cocoa powder, milk permeate, and vegetable oil that would be structurally strong enough to support the pavilion’s own weight at room temperature. We tested the compound mixtures and found that the strength-to-weight ratio of chocolate compounds is quite low — about 24 times lower than standard concrete.

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Testing material properties in the lab

After deliciously physical experiments with chocolate pneumatic shell forms, inverted tree networks, saddle forms and hanging fabric models, we settled for a hanging fabric shell model as a form finding approach for the pavilion. With only the self-weight of the chocolate to carry, this catenary form was the most structurally efficient. As long as creep and global buckling were considered in design, it provided a structural system that could span the farthest using the smallest amount of material. Although it was appealing to exploit the rheological properties of the chocolate and explore flows of forces by pouring material onto formwork or dipping material, the practicality of this application method would break down at a large scale with a limited construction time frame. Considerations such as control over material thickness, adherence to support formwork (whether flow over steep formwork or accumulation on a set of strings), the setting speed of chocolate, and assurance of a monolithic form raised large construction challenges.

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Four different physical form-finding approaches explored for chocolate compound material. Left to right: pneumatic shell forms, inverted tree networks, saddle forms, and hanging fabric models. The last model was selected.

We developed a digital parametric model that integrated form finding, shape optimization, planarity mold, and patterning algorithms. The prototype we built consisted of over 70 individual frames of chocolate that puzzled together into an open-air domed pavilion. This real-life chocolate pavilion seemed to come straight out of Willy Wonka’s chocolate factory.

Digital and physical instances of the parametric design to construction workflow
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Experimenting with mold forms, materials, and connections
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Chocolate Plated Grid Shell Pavilion (Image credit Axel Kilian)

This blog post is based on Alex Jordan *13’s research towards a masters thesis. You can find more about our project here.

Author: Sigrid Adriaenssens

Editors: Jacob Essig, Demi Fang ’17

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Our Summer Rammed Earth Experiments 1/3: The Golden Spiral for Forbes Garden


Dirt—as in clay, gravel, sand, silt, soil, loam, mud—is everywhere. The ground we walk on and grow crops in also happens to be one of the most widely used construction material worldwide. Earth does not generate CO2 emissions in its generation, transport, assembly or recycling and this in contrast to more conventional building materials such as concrete and steel. In rammed earth construction a mixture of  clay, silt, sand and gravel is compressed into a formwork to create a solid low-cost load-bearing wall. Despite the renewed architectural interest in contemporary rammed earth construction in (semi-)arid climates of the USA, little is known about its potential in the erosive humid continental climate of New Jersey. Because of the great potential of rammed earth as a local building material, we decided to design and construct a spiral rammed earth structure in Forbes Garden that will be an enduring representation of Princeton’s effort to create a campus containing sustainable and elegant zero carbon architecture.

The Material:  Dirt

The Form Finding Lab’s team established the suitability of Princeton soil for earth construction though an extensive set of laboratory tests. The team, led by PhD candidate Tim Michiels and supported by undergraduate student Amber Lin ’19 and summer intern Jacob Essig, subjected a series of compacted samples with different water contents to compression tests (the rammed earth samples had an average compressive strength of 1.35 MPa). The team also experimented with lime additives  (3%, 5%, 10%, and 25%)  to test the compacted dirt’s resistance to weathering on a series of prototype walls (See image above title).  All these results informed the design of the structure that was designed for Forbes Garden as part of the Campus as Lab Initiative .

Testing of compacted samples with different dirt compositions to establish unconfined compressive strength. The local soil was composed of 19% gravel, 42% sand, 24% silt and 15% clay.

The Site: Princeton Garden Project

The Princeton Garden Project at Forbes College is a student led initiative that supports and advances sustainability and food awareness  on Campus. Following with its mission of sustainability, the rammed earth spiral is a sustainable experiment made with local and abundantly available materials intended to enhance the existing organic garden and transform it into a space for research and learning.

The Garden Project, the ideal collaborator for a rammed earth project (image credit Garden Project at Forbes College)

The Design:  A Site-Specific Golden Spiral

Spirals occur all throughout nature. For example, we see them in the trajectories of sunflower seeds and pine cone kernels in Forbes garden or in the pictures of Karl Blossfelt (1865-1932).  We adopted this familiar shape and designed the Forbes Garden spiral as a golden spiral, a type of logarithmic spiral whose growth factor is the golden ratio. We positioned the spiral with respect to the sun in high summer so that the structure would cast shade. To further enhance the visual aesthetic experience of visitors, we worked to ensure that there was a straight line of sight from the lower part of the swirling wall, which serves as a bench, towards the Gothic Cleveland tower and carillon which dominates the Graduate College landscape. To invite visitors to spend time in the garden and experience the raw and minimal character of the  structure, we designed the lower part of the spiral as seating. The size of the swirling curve was fixed by anticipating the range of comfortable distances from a fire pit, which will be placed in middle of the semicircular slower section. As the bench slopes gently upward from a minimum of 40 cm, it allows comfortable seating tailored to garden-enthusiasts of different heights. The bench is furthermore separated from a wall that reaches a height of 3 m to allow for different seating heights on the lower end, as well as to ensure sufficient clearance for a sense of openness of space at the higher end, where a shading roof is planned. Additionally, the wall’s varying height needed to be adapted to match the slope of the uneven terrain of the garden. These constraints, together with structural stability considerations, informed the development of the 3D shape of the Spiral. Stay tuned for our next post  to find out how we figured out how to build such a complex geometry in dirt!

Spirals in the plants photographed by Karl Blossfelt
Site plan showing sight lines, seating and the sun’s position at high summer
3D rendering of the golden spiral for Forbes Garden Project

Author: Jacob Essig

Project by: Sigrid Adriaenssens & Tim Michiels

What I am Thinking: Reflective Practitioner and Educator Eric Hines

“The two worlds of practice and teaching are hard on each other. To live between them is kind of hard because you get pulled in both directions and don’t get a lot of sympathy from either side. I’ve learned how to be flexible and strong in certain ways by running between the two,” Prof. Hines says. “Going into it, I had more literal expectations: ‘let’s do some research, let’s advance the state of the art, let’s teach the students about our buildings’. But the good stuff is a level down from that: it’s about the people, how we understand things, how we do our work, how we fail and recover, how we succeed, and how we support each other.”

Tufts University Civil & Environmental Engineering Professor of the Practice Eric Hines takes one of his classes on a tour of the building projects his company was working on in Post Office Square. Photo: Tufts University

I first heard of Prof. Eric Hines as a rising sophomore at Princeton working with Prof. Adriaenssens in building on her existing Mechanics of Solids course. At the time, we drew much inspiration from Prof. Hines’s compelling pieces of writing on education and creativity in engineering, such as his series “Principles in Engineering Education” and his essay “Understanding Creativity.”

It is no coincidence that he wrote for and co-edited the Festschrift Billington 2012, a series of essays written in honor of Princeton Civil & Environmental Engineering Department’s Emeritus Professor David Billington; Prof. Hines was a graduate of the Princeton CEE Department himself. It was thus inspirational to meet Prof. Hines last week at Tufts University, where he has taught since 2003. As Professor of Practice in the school’s CEE department, he divides his time between Tufts and the LeMessurier engineering office in Boston.

Being in practice has forced Prof. Hines to think carefully about what he brings to the classroom. He expressed frustration that while the theoretical examples presented in textbooks are useful in helping students grasp concepts, “when you’re working in the real world on design, the real world doesn’t divide itself neatly up into little ideas.” In real problems he encounters in practice, “the ideas are important for understanding, but all these wild things happen: they intersect and pull over on each other, they become complex and even ironic in their intention… In the classroom, I like to have a real example, but the real examples are messy and difficult, and it can be hard to turn them back into theory.”

Prof. Hines’s internal struggle reflects his desire to stay true to the first principle he outlines in his essays: Theory and practice are indivisible. While he strives to clearly teach theory to his students, as a practitioner he also wants to show students how reality can cleverly disguise theory.

Does he still give students these more complex and realistic problems in the classroom? “Luckily, I can usually pull from the examples I’ve crafted over the years, but it in general takes an enormous amount of effort to take a real problem and to distill it into something the students can use,” he answers. “Unfortunately, we don’t really invest enough effort in academia in creating good learning examples– it’s a pretty profound form of intellectual activity, but the American university system hasn’t quite figured out how to reward faculty for this kind of engagement. Our culture in general, and thus also in our universities, is very concerned about what can be measured. If we could step back and have a deeper conversation about the immeasurable things that give our lives and our work their true value, we might develop a stronger capacity to pursue important things that can be hard to measure.”

When you’re teaching, you’re constantly trying to explain yourself to young people– a good audience, but a tough audience in terms of demanding a level of clarity. I bring that into my practice with me.

While his practice has inspired him to rethink teaching, his teaching has also changed the way he approaches engineering practice. “If you’re only ever practicing, you get used to the real world and the compromises you make, you get used to not being able to rationalize and justify everything because some decisions get made for different reasons. But when you’re teaching, you’re constantly trying to explain yourself to young people– a good audience,” he adds, “but a tough audience in terms of demanding a level of clarity. I bring that into my practice with me, and sometimes it feels like a curse because it’s much easier to go about my work without having to think about how I might teach things. Over the years, though, this idea of always needing to clearly explain every step really affected me in terms of how I did my calculations, developed my drawings, and talked to people. And this really allowed me to communicate between the two worlds of teaching and practice.”

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Prof. Hines shares some of his drawings and calculations of an elliptical roof.

His students have also taught him valuable lessons on the nature of creativity, communication, and risk-taking. “With my students I learned a lot about how people– not just students– can be self-conscious about what they know and what they don’t know. Over the years I’ve become more comfortable with this kind of discomfort. Anytime you’re in a truly creative process, you don’t necessarily know what’s coming next, and that can be frightening. I think I’ve learned a lot about how to be in that process.

“There was a point when I realized that engineering is all about language. The thing about language is that we never get it right the first time around; language is this medium in which we put all this stuff on the table and think about developing the ideas so that the words and the drawings are the same. Language is this place where you can make mistakes. After that realization, I began to consider my calculations as a way to record the thoughts I was having in that space and in that moment, and I stopped worrying about the mistakes and trying to be right all the time.”

Engineering is all about language. The thing about language is that we never get it right the first time around… Language is this place where you can make mistakes.

This encounter with Prof. Hines is not the first time we have spoken about practitioner-professors of structural engineering on this blog: we touched on this idea while speaking with Mr. Helbig of Knippers Helbig and most particularly in our reflections on a recent symposium on Japanese structural engineering. I took the opportunity to ask Prof. Hines on the question that had been on my mind: why is it so common for engineering practitioners to be in academia in countries like Germany and Japan, but not in the US?

“That’s a very good question and worth writing a senior thesis on! I don’t know what you’re writing your thesis on–” (funny, neither do I)– “but you could write your thesis on the history of how the American academic system evolved to be the way it is. I could start to talk about the whole history, but we’d be sitting here for a very long time.” The divergence in cultural conventions originates as far back as the Industrial Revolution, he says, citing moment diagram conventions as one example of the divide: “The American academic approach is to put the diagram on the compression side of the member. The European approach, which is an approach that more designers that I know of have taken, put it on the tension side of the member; this allows the moment diagram to resemble the deformed shape. It’s really interesting how conventions and history and all these things can shape everything we believe in and what we think.

“A lot of how we think about science and math goes back a very long way, to the point that we have developed certain prejudices about how things happen. What I mean by ‘prejudice’ is that we learn certain concepts as dogmas; we think it’s ‘this way’ to the exclusion of thinking any other way.”

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One of Prof. Hines’s principles of engineering is that “drawing is the language of the engineer.” Pictured here is another set of drawings and calculations from the elliptical roof.

Prof. Hines touches on one of his other principles as a final illustration of some engineering aspects that are not so embedded in American culture: Drawing is the language of the engineer. “Every professor I know who writes papers in engineering, we all do the same thing: we start with the figures and write the paper around the figures. We begin with the visual language. But somehow in the US we treat drawing with this strange duality– drawing is either a technical skill, or it’s this artistic and abnormal gift. There was never a place where drawing was just part of the culture.

“Engineering in many ways is a discipline that needs the visual to be right in the middle of the culture and to be normal.” He compares visual language to the language of words: “Sometimes I write a nice essay, sometimes I write a formal document, and sometimes I write a love letter. Sometimes I say something cool, and sometimes I say something stupid, but it’s not like I can only say things that are polished and flawless.” It’s the same with drawings in engineering, he explains. “Sometimes the drawings look nice and beautiful, and sometimes they’re really quick sketches. You can imagine how frustrating it would be to expect every stage in the creative process to be this profound work of art.”

So he doesn’t. Drawing is the language of the engineer, but only after the engineer learns to embrace the visual language as a sometimes imperfect mode of communication.

After graduating from Princeton University with a BSE in Civil Engineering and Architecture in 1995, Prof. Eric Hines went on to do a Fulbright in Stuttgart, working at Schlaich Bergermann & Partner and studying the history of Jörg Schlaich’s structures. He admired Prof. Schlaich’s career which intertwined practice and academia; he is now Professor of Practice at Tufts University and Principal of LeMessurier Consultants in Boston, MA.

Author: Demi Fang ’17

A Physical Costa Surface 3/3: Building the structure

The fabrication of a tensile structure is a complex design process. How can the mathematical shape and the form found geometry derived in the first and second parts of the series be used as the basis for a sculpture? In this final post of the “Physical Costa Surface” series, the Costa Surface sculpture takes shape.

The dimensions of the sculpture are 1.5m of height and 2m of diameter. In order to build the sculptural installation, four steps are necessary: patterning the surface, designing the interaction between compressive and tensile elements, cutting the fabric and assembling the pieces.


Thread direction in fabric – the warp direction is often prestressed during manufacturing

The first task to making this surface a physical reality is patterning. This operation is maybe the single most important in the design process. The success of the patterning will in part determine if the tensioned surface will wrinkle or not. Fabrics used in engineering projects have generally a high level of anisotropy with warp and weft directions of the weave determining the material properties. In loom manufacturing, the warp direction is generally pre-stressed while the weft is weaved. In our case we used a high quality nylon/spandex fabric presenting a four-way stretch (ideally equally stretchable in warp or weft). The fabric can accommodate large strains so the risk of wrinkling is minimized.

We performed the patterning on the initial mesh geometry of the form finding procedure (details can be found here). In this process three distinct patterns are produced. The figure below shows how the patterns are distributed over the surface. The patterns are shrunk to compensate for the pre-stress and large strains in the membrane.

Patterning of the 6-hole Costa surface

Interaction tensile / compressive elements

The visuals of the structure have been so far limited to the surface itself. The constraints of the mathematics are fixed boundary conditions. The constraints of the fabric impose the application of the tensile stresses. These will in turn modify the position of the boundaries.

In order to create rigid circular boundaries, 3/8in. (9.5mm) glass fiber reinforced plastic rods were used. They were bent into 1.5m  (top and bottom) and 2m (center)  diameter circular hoops and connected by aluminum sleeves (ferrules).

The top and bottom rings are equilibrated by bending active GFRP rods. As seen in the figure below, by being bent, the rods push the two rings apart. The actions of the rods are equivalent to the thrust of an arch, providing the necessary force to achieve a height of 1.5m as specified in the computational model.

Building the sculpture


Graduate Student Xi Li with the initial Paper Model

A relatively large scale (1-2 meters) was chosen for ease of fabrication, thus a large quantity of fabric was required to produce the final product. Before handling the fabric however, the final patterns were cut on paper and a smaller scale paper model was created. The paper model served two important purposes. First, assembling the paper model provided insight into the most efficient sewing sequence. Since the model was to be sewn entirely by hand, arranging a way to avoid attaching fabric pieces at awkward angles given the constraints of the sewing machine was crucial. Secondly, the pieces of the fabric model were labelled and served as a “map” during the sewing process to keep track of the pieces of fabric (24 total).

After successfully constructing the paper model, MDF patterns of the three patterns at full scale were lasercut. The final patterns were adjusted to accommodate seam allowances for attaching edges, and allowances for sleeves to hold the rods that would form the three rings. The MDF templates were used to trace the patterns onto the sheets of fabric, and were cut out by hand. The pieces were carefully sewn with a commercial sewing machine in the sequence below.

Sewing Sequence

Once all of the pieces were properly attached, the fiberglass rods were inserted into the pre-sewn sleeves to create the rigid circular boundaries. As they were inserted, they were connected with specially designed, 3D printed connectors in order to insert six additional bending-active rods to push the top and bottom rings apart. Once the buckled rods were inserted, the Costa Surface model sat at the design height of 1.5m, fully tensioned with no wrinkles.

Built structure

Final Model (Whole)
Fully Assembled Costa Surface
Final Model (Buckled Rods)
View of Buckled Rods and Connectors
Final Model (Whole) 2
Finished Sculpture

Author: Victor Charpentier and Tracy Huynh

Designed and Produced by: Xi Li, Victor Charpentier, Max Coar, Tracy Huynh and Olek Niewiarowski, graduate students at Princeton University


Design-and-build bamboo shells

Bamboo is a building material that lends itself excellently to the construction of sustainable gridshells. Two of the Form Finding Lab’s graduating senior students, Lu Lu and Russell Archer (’16), worked under the guidance of PhD candidate Tim Michiels and Professor Adriaenssens on the analysis of a set of hyperbolic paraboloid (hypar) gridshell roofs in Cali, Colombia. The Form Finding Lab’s team collaborated closely with the design team of Colombian-based Spanish architect Greta Tresserra and her team to improve the structural understanding of gridshells made from locally sourced bamboo. Follow Lu Lu and Russell’s adventure in this video:

Senior thesis: Sustainable building with bamboo from Princeton University on Vimeo.

Bamboo Gridshell Hypar in Montebello, Colombia

Colombia is home to the giant American bamboo species Guadua Angustifolia. Guadua, a type of grass, can grow up to 18m tall and obtain its full height in a mere 6 months. Moreover, it can be harvested and treated for construction purposes after 4 years requiring relatively little effort. The speed of growth of bamboo and the ease of its harvesting is in stark contrast to the time and resources that are required to obtain wooden lattices, a typical material used for gridshell construction. Moreover, architect Tresserra only employs traditional, low-tech joint techniques in order to make expressive and elegant guadua construction accessible to less affluent communities.

Guadua bamboo culms are straight hollow tubes with interspersing nodes about every 20 cm along its length which act as diaphragms. The guadua tubes are thicker than typical bamboo poles, which makes them much stiffer, which is why it makes most sense to employ these straight poles as rectilinear elements in construction. Hypar surfaces, revolutionized by Felix Candela in his concrete shells in Mexico, can be made out of just straight elements, allowing for an elegant forms from simple elements.

Russell’s senior thesis focused on the most important joint in these guadua structures, the fish-mouth connection. Lu Lu performed an in-depth parametric study on one of the hypar structures, allowing to improve the structural behavior of the roof. Lu Lu and Russell, traveled together to Colombia to visit the bamboo structures and optimize their analyses in collaboration with the Colombian team. Tim followed up on this visit, by providing further assistance in Cali on the seismic analysis of these grid shells. Overall, the Form-Finding Lab’s efforts will have an impact in Colombia, as the eventual design of the structures will be optimized using the input of the team. Construction is about to start in the upcoming months!

Russell Archer and Lu Lu during their visit in Colombia.

Author: Tim Michiels