stp labs

stp labs

Friday, September 19, 2014

Saarinen's Shells and the Emerging Influence of Engineering

Saarinen's Shells

“(The) structural and rational cannot always take precedent when another form proves more beautiful. This is dangerous but I believe true.” Eero Saarinen, dictated reflections, “General Statement about the sculptural, curved shapes…”, between 1958-60.

Much of my research over the last few months has been centered on the confluence of two of my favorite topics: Eero Saarinen and structural shell design. Luckily, I was able to present this research this week at the International Association for Structural Shells (IASS-SLTE) in Brasilia—I couldn’t have picked a better venue or audience (more on the intriguing content of the conference in a follow-up post).

I’ve spent a great deal of time studying and writing about Saarinen over the years because I feel that the range of his work, and the way he approached his work, is incredibly instructive. He wasn’t always good, but frequently he was GREAT. And most importantly, when he was bad, he was bad in a way that is actually quite instructive.

He was a prolific designer with a prodigious mind who intentionally ran toward the untested realm of architectural creation—frequently experimenting with structural technologies, new materials, and/or new construction methodologies to inform his designs. 

Like all experiments, there were some incredible results, including some very instructive failures that I’ve written about previously

Saarinen was a brilliant man, surrounded by the brightest young designers (Roche, Dinkaloo, Pelli, etc.), but architects aren’t solely responsible for all their innovations (or the failures). The large percentage of projects Saarinen’s office designed required experimental structural engineering work and they primarily worked with two different firms: Ammann & Whitney and Fred Severud.  

Because of their expertise in concrete shell design and analysis, Ammann & Whitney worked on the shells projects (Kresge, TWA, Dulles, etc.) while Severud (one of the leading experts in tensile structures) worked on the Gateway Arch, Ingalls Hockey Rink, and the majority of Eero’s other work.

Engineering Influence:

“In many cases (Saarinen) has relied upon the sheer ingenuity of modern technology to get him out of difficulties that would have presented insurmountable obstacles a quarter of a century ago” – N. Keith Scott, Architectural Forum, Feb. 1955.

The research started when I wondered, what effect did Eero’s relationship with his engineers have on the development of his work on structural shells of Kresge Auditorium, TWA Terminal, and Dulles Airport? 

In only ten years the work went from very bad structurally (Kresge), to a more coherent and stable (albeit very unconventional) structural form for TWA Terminal, to the highly efficient and optimized structural form and architectural expression at Dulles. Saarinen went from Shape-Finding to Form-Finding (more on this in a future post as well). 

But HOW did this happen? Saarinen was very busy (working simultaneously on his other master buildings: GM Tech Center, Jefferson Memorial, Ingalls Hockey, John Deere headquarters  etc.), so he certainly relied on others for help in developing the projects. More specifically who, or what, caused this evolution in technical competency and structural form optimization? 

I set out to try and determine the nature his collaborative relationship with the engineers; specifically trying to determine the extent of influence that was exerted by engineers during the design process. These simple questions have profound implications on the historical reading of Saarinen’s work.

Interestingly, this topic is largely un-documented in any previous scholarship and I found it frustratingly difficult to reassemble as most original records of direct correspondence between the firms have been destroyed or misplaced at both the Saarinen Archives and at the firms.

In sorting through the remaining drawings, letters, and records of many projects at the wonderful Yale Manuscripts and Archives library, I’ve been able to piece together a few conclusions (I will link to the final paper once it is available at the ISU Digital Repository).

There was a great deal of interesting work done by the professional publications at the time (Progressive Architecture, Architectural Forum, etc.) but the really insightful information often came from construction and engineering publications (Engineering Record, etc.) as they tended to focus on how it was designed and built instead of simply the architectural implications of the unique forms.

I had my research assistant Barrett Peterson help me put together a series of drawings that showed the construction process of Kresge and Dulles using parametric modeling. We were trying to understand how a particular economy of construction could also be evidence of an efficiency in the design process and structural form. The drawings were great and very informative but they weren't definitive about the source of the improvements; they simply indicated what we already knew....the projects got better. 

The breakthrough in the research, and frankly one of the highlights of my academic and professional career occurred when Eero's former partner, Kevin Roche (obviously now of the legendary firm, Kevin Roche + John Dinkaloo Associates) agreed to talk with me about the projects.  

Even though Mr. Roche is 92 years old, he was able to remember detailed circumstances and stories about the design development of all of the projects (he was frequently pictured next to Eero during the legendary model making process). His stories confirmed many of my suspicious about the changing design process (yes the engineers were collaborators) but he also clearly gave the primary credit to Saarinen's evolving clarity of vision for the designs. 

Shape Finding and Form Finding

“…the reason why these (plastic forms) are being built now…is really aesthetic and not economic; and we should face that.” Eero Saarinen, Speech to Architectural Association, August 1957

Things started badly with Kresge. Because its shape wasn't a viable structural shell form for a thin shell (1/8th of a sphere supported on only 3 points is NOT a funicular shape) it performed terribly.  It was a nightmare to construct and it had terrible structural performance. After the scaffolding was removed, it went through 6 weeks of unabated creep, eventually sagging 5" total at the arches. The scaffolding was put under the building again until the window system under the arches could be changed to a structural system that would support the arches....basically is wasn't transferring loads like a shell should at all.  Ed Salikis at Cal Poly called Kresge the "Angel of Death" for structural shells because these truly fundamental problems greatly affected the perceived viability of these types of structures.

A Common Cause
Things got better with TWA because Saarinen involved the engineers earlier in the process and listened to their feedback throughout the design development. Saarinen was unsatisfied with Kresge (primarily for aesthetic reasons) and he really wanted TWA to not feel as "earth-bound" so he asked Anderson to help develop an elliptical paraboloid upwardly curving roof.  Eero didn't need help in finding the form (he sketched in on a menu at dinner before talking with anyone else about it) and he had drew a legitimately viable structural form. The issue came when Saarinen didn't feel that the building was formally expressive enough about the system of movement going on inside the building.

The simple structure shape was changed to look more like a series of four shells combined in one  big roof. Roche tells me that Saarinen was clearly influenced by Utzon's design for the Sydney Opera House---after all, it was Saarinen that picked the project out from the discard pile and convinced the jury of the design's merits.  But the Anderson, and the other project engineer, Abba Tor, told Saarinen that the shape simply wouldn't work as a shell (the folds would take bending, it couldn't be poured without control and expansion joints, etc.).

“It took a considerable amount of interaction with the architect to impose some structural logic or discipline on it…it was a creature which started out wild and needed to be tamed and domesticated.” – Abba Tor, Ammann & Whitney

Mr. Tor takes credit for pushing the design from this stage to it's final iconic form of four separate cantilevered barrel vaults joined in the middle. Roche disputed this and claimed that it was Saarinen who insisted on the four shells in order to create the roof skylights that would better light the way for travelers below. I call it a tie. In fact, it doesn't really matter who's idea it was---it was the right idea for the architectural design and the structural performance.

Expressing Time and Convenience: Dulles

“We tried to give a completely logical, imaginative, and responsible answer.” – Eero Saarinen, 1960

Interestingly I found that Ammann & Whitney was the contract holder for Dulles (Saarinen worked for them). The firms immediately set out to study all the major implications for jet travel around the U.S. (as it was an untested phenomenon). Famously, representatives of both firms completed a detailed analysis of existing airports in an effort to understand how the movements of passengers and jets could be optimized to provide a more convenient, flexible, and effective set of operations. Ultimately Saarinen proposed the use of “mobile lounge” vehicles to transport passengers from the terminal to the jets allowing the terminal building to be smaller, more efficient, and more precisely illustrative of its purpose—the building form was intended to express this. Saarinen asked his friend Charles Eames to make a film about it to convince everyone about the merits of the idea. 
 
The rest of the design was all about emphasizing and enhancing this system of movement and efficiency. The design need to accommodate expansion, so instead of creating the difficult double-curving shells like Kresge and TWA, Saarinen focused on easily repeatable and developable (or extendable) building sections to create a large open room under a sweeping roof flanked by colonnades. Saarinen clearly sketched out the idea, including a proper catenary shape for the roof and columns that intuitively lean outward to resist the forces. Because the form expressed an inherent structural logic, very little about the building’s concise and elemental form was required to change for either architectural or structural reasons; the main collaboration efforts were in the translation of this simple design idea into an efficient but expressive structure. Also interestingly, they developed very efficient and effective means of construction. 

Remarkably, the main roof was constructed without any scaffolding because the catenary curve of the roof wasn't cast in place as many people believe, but was instead made up of lightweight concrete precast panels that were slid down along a series of cables. They were eventually poured together to get the lateral stability and resistance to uplight that they required structurally. Because the structural elements were regular and repeating, multiple trades could be working simultaneously as construction progressed from one end to another. I will talk more about this during a presentation at the upcoming International Construction History Conference in Chicago, but this process of construction was so much more effective and efficient than Kresge that it is quite notable.

Imparting Influence
“I think this terminal building (Dulles) is the best thing I have done…Maybe it will even explain what I believe about architecture.-Eero Saarinen (as quoted by Aline Saarinen), 1962

It is clear that the incremental evolution in the structural responsiveness and constructability of these shell projects can be largely attributed to Saarinen’s willingness to accept and embrace a greater level of influence and expertise from the structural engineers during the early stages of design formation, and the correspondingly increased level of expertise in shell design by the project teams in both offices born from this collaboration. In other words, the more these talented firms worked on shells together, the better they got in designing, documenting, and constructing them.

Sorry for my absence in blogging regularity, but as I always, I appreciate you reading and sharing the work.