What I am Thinking: Thorsten Helbig on Curiosity and Collaboration in Engineering

Despite my arriving twenty minutes early to Knippers Helbig’s office in New York’s financial district on a brisk Friday afternoon, I am warmly welcomed at the door by an engineer whose work I probably just interrupted. As he goes to summon a man around the corner, I peek at the office space: not enormous, but still spacious and pleasant, giving no sign of being too small for the number of engineers at work. Thorsten Helbig, principal of the Germany-based engineering firm Knippers Helbig (KH), emerges immediately, equally warm and welcoming as he ushers me into the office’s conference room. The room opens up on two sides to the office space, and Helbig goes to shut both doors; despite the auditory privacy, the work carried out in this room is always transparent: one wall of the conference is a glass window, allowing any passersby to glimpse at our meeting through the satisfyingly enormous letters “KH” staining the glass orange.

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The Knippers Helbig office space at 75 Broad St, New York. © Knippers Helbig

It is perhaps no coincidence that the office space articulates such clear architectural considerations. Helbig’s approach towards meshing engineering expertise with architects immediately becomes our first and most fruitful point of discussion. “In a relationship between engineer and architect, I think what is most important is that there is mutual respect and a communication,” Helbig asserts. “Ideally, the communication starts very early in the design process.” In many projects, he explains, Knippers Helbig is involved from the very beginning—ideally, at the competition stage—to the final completion and execution of the project. From the start, every decision made by the architects in organizing the program leads to consequences that require the engineers’ input regarding limitations such as soil conditions, column spacing, and slab systems. Inevitably, the engineers put forth decisions and recommendations that influence the project’s appearance, but Helbig underlines that “we as engineers should not try to be architects, but rather maintain an engineering perspective.” Projects can benefit so much more from an engineer’s engineering contribution, Helbig points out. “At the same time,” Helbig qualifies, “I expect that everybody at the table has a qualified opinion. As an engineer, we can question some of the architect’s decisions, which can—in the best case—make the architecture even better.” Helbig says that while there exists the notion of signature architects, he doesn’t believe in “signature engineering.” We can look at some buildings and often guess at the architect, but Helbig doesn’t find it “right” to be able to do the same with the engineers of building structures, even if the engineers’ contribution can be clearly read in many building types. “As an engineer, I want to be able to support architecture. We start with the same open-minded approach in every collaboration, but it consequently leads to different results when we work with Massimiliano Fuksas, Renzo Piano or Liz Diller because their individual architectural approaches require individual engineering solutions. I see us as collaborators in exploring the inherent potential of the architectural intention – and sometimes innovatively engineered parts act as catalysts for specific architectural expressions.”

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World Water Day: how prestressed membranes matter when every drop counts.

World Water Day happens on the 22nd of March every year to bring awareness to the global water crisis. In my class CEE546 “Form Finding of Structural Surfaces” architecture and civil engineering students were collaborating today on the design of a water harvester that doubles up as a community center canopy for disaster struck areas. The idea is that an anticlastic membrane roof structure can be shaped to collect water in shipping containers while also shade and shelter the community it serves. The students learned together how to make physical small-scale models of prestressed textiles and refined their design in commercial form finding software that employs the force density method. The resulting designs were reviewed by Prof. Ruy Pauletti from Sao Paulo University, Brazil and myself. I will write more about him in later post. The resulting designs show novel water harvester/canopy systems that draw on the excellent structural behavior of pre-stressed membranes.

Project 1: Cone design – Iwanicholas Cisneros and Hannah Guo


Project 2: Asymmetric cone design – Isabel Morris and Kaicong Wu

Project 3: Arch and membrane design – Pelin Asa and Rebecca Napolitano


Project 4: Saddle design – Lu Lu and Sharon Xu

Project 5: Arch and membrane – Mauricio Loyola and Olek Niewiarowski

Author: Sigrid Adriaenssens

How do we experience Candela’s shells today?

Last January Dennis Smith (’16) had the opportunity to travel to Mexico City where he visited five of Felix Candela’s best-known structures: the Chapel of Lomas de Cuernavaca; the Church of San Antonio de las Huertas; the Church of the Medalla Milagrosa; the Cosmic Rays Pavilion; and Los Manantiales restaurant. Here he talks about his experience:

“One of the most striking things I noted on the trip was how Candela’s structures were very much integrated into their surroundings and were no longer the standalone structures they used to be when built. At Cuernavaca, trees have been planted all around the front of the chapel, obscuring most views from that side. The other two churches are on busy city blocks, while the Cosmic Rays Pavilion is in the middle of one of the university’s recreational areas. At the Manantiales restaurant, posters cover all the windows and light bulbs pepper the underside of the shell, while the outside is largely obscured by fencing and trees. At the same time, people who use these structures seem unimpressed. For example, the restaurant worker who allowed me to enter Las Manantiales was surprised that I could spend over an hour looking around. Overall, I greatly appreciated the opportunity to personally experience these structures close up.”

Approaching Los Manatiales through the parking lot, January 2016 (photo credit: Dennis Smith)
Los Manantiales restaurant interior; the windows are covered by posters (photo credit: Dennis Smith)
Exterior Church of the Medalla Milagrosa, the power lines seem to form a ruled surface (photo credit Dennis Smith)

Continue reading “How do we experience Candela’s shells today?”

What I am Thinking: Structural Designer Of The Millennium Wheel And Role Model Jane Wernick

In the coming decade, the United States will have to add 250 000 civil engineers to its workforce in addition to replacing those who will retire. However, only 12.2% of the current American civil engineers are female. These statistics indicate the need to encourage young people, especially from underrepresented groups in civil engineering, to pursue engineering opportunities in their education.  As a PhD student in the 90’s I met the structural designer Jane Wernick at the IASS conference in Denmark. She offered a positive influence on my educational and career plans. A few years later I ended up working with her at her own engineering consulting office Jane Wernick Associates (London, UK). Jane believes that structural engineers can have a great impact on the built environment and hence the quality of life of people, yet they have to remember that they have a huge responsibility to the planet and its sustainability. She states that her biggest achievements are “.. my involvement in the Millenium Wheel and starting my own practice”[1].

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What to wear to the Oscars?

Do engineered systems play a role in Hollywood style?

Engineering is all around us, whether we recognize it or not, from the homes we sleep in, water we drink from, and roads we drive on.  Have you ever thought engineering could play a role on the Silver Screen?  Perhaps you think engineering systems don’t impact Hollywood, but here is an example of the impact of form in a romantic drama…

In the book Atonement, by Ian McEwan, as well as the movie, a love story is told between Cecilia Tallis and Robbie Turner.  The two young cross paths at an eventful dinner, but are torn apart by lies.  The author, Ian McEwan, spends pages of the book focused on Cecilia’s choice in dress for the occasion.  She finally chooses a “bias-cut”, emerald dress which accentuates Cecilia’s figure, causing heads to turn and hearts to ache.  In fact, the actual dress Kiera Knightley wore in the movie was recently voted “Best Costume of All Time” by Sky Movies and readers of In Style [1].  So what does this have to do with engineering?

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Screenshot of Keira Knightley wearing a bias-cut emerald dress in the movie Atonement [1]
The key word is: “Bias-Cut”.  This refers to the orientation of the fabric threads.  A fabric’s grain is determined by the direction of the warp and weft threads of the fabric which changes depending on the direction in which the material is cut.  This direction affects the response of the material in tension.  Does your shirt stretch more in one direction than the other?  How does this compare to the direction of the threads?

On the left is a diagram of the thread directions in fabric.  On the right is the direction in which the fabric can be cut.

During the 1930s and 40s, when this love story takes place, most garments were cut straight across, so that the grain ran parallel to the main, or warp, threads.  All material has some self-weight, and in garments this causes vertical tension in the weave.  When cut cross-grain, the cloth deforms very little when draped, especially if the weave is tight.  For example, the pink dress (on the left) has a stiff thread structure.  The form of the dress is largely determined by the orientation of the threads that make up the material, little deformation of the material occurs when it hangs under its own weight.


Cross-grain cut dress (left) and bias cut dress (right)

On the contrary, material that is bias-cut has been cut at a 45 degree angle to the warp and weft threads.  The initial square mesh becomes a diamond shaped thread pattern when the material hangs.  Under increased downward tensile loads, these diamonds have greater deformation and produce high lateral contraction.  You can see in the gold dress (on the right), that bias cut and lateral contraction creates a closer, more form-fitting shape of the dress.

The grid on the left under vertical tensile loading deforms to the grid on the right.

However, not every material will have this dramatic draping effect. For example, a paper dress would not have hang the way Cecilia’s does in Atonement.  The amount of lateral contraction under tension is dependent on the shear modulus, a measure of the elasticity or rigidity of a material under shearing force, of the material.  A higher shear modulus means the material is more rigid and deforms less under shearing.  Materials with low shear moduli, like silk and cotton, deform easily making them desirable in dress making.  So perhaps the shear modulus of silk can partly be to blame for Keira Knightley’s glamorous Hollywood look.

We would like to thank  Keating Helfrich, Lewis Center of the Arts, Princeton University  for lending the pink and golden dresses to us, and Aatish Bhatia for creating the mesh animations.

Author: Kendall Schmidt