Modernist Architecture promised to imbue the realm of design with contemporary advancements through marrying technology and aesthetic form. Although the movement can be criticized as a period more often conveying futuristic ideas in composition than construction, the challenges posed by more forward-thinking designs demanded clever and innovative uses of technology. Completed in 1965, Eero Saarinen’s Mid-Century Modern marvel the Gateway Arch in St. Louis, Missouri exemplifies design’s interrelationship with technology. From conception through construction, and into daily operation, the exceptional nature of this design posed some particularly unique challenges to all involved.

How Does it Stand?

From brazen designs to banal, most buildings require columns and beams as part of their internal assembly. However, this catenary construction has no structural skeleton, and instead relies on its own skin for support. Truly monumental in scale, the Arch’s legs stand 630’ apart from one another, or more than two football fields. Comprised of stainless steel and carbon steel plates, the double-walled structure then rises 630’ into the air through triangular segments gradually decreasing in size from 54’ per side to 17’. In addition to strengthening and post-tensioning rods, concrete was pumped between the double-walled sections for the first 300’, while the sections above integrate steel framing. With no orthogonal internal regularity, conventional construction methods were not an option for this constantly curving structure.

 

Eero Saarinen amongst some of his test models and sketches exploring the Arch’s catenary curve.

So, how was it Built?

The first 72’ were fairly straightforward, ground supported creeper cranes lowered the sections into place. However, with the Arch’s height and lack of internal structure for platforms, building above those initial segments presented a challenge. Although a relatively new technology at this scale, creeper derricks were utilized on either side of the Arch. With adjustable supports, each 100-ton derrick with a platform would pull itself along the Arch’s side, staying level despite the changing curvature. As the curve increased with construction, the derrick’s telescoping legs would shorten, new track would be added and, much like a train on a rail, the derrick would creep up the newly placed segments. Initially, the Arch’s two legs acted as free standing cantilevers, but their increasing weight necessitated a scissor truss for the final 100’, which the derricks lifted into place. The Arch became self-supporting when the final section, containing an observation area for the public, was lifted into place.

Creeper derricks lifting the scissor truss into place.

Wait, how do I get up there? Do Elevators go sideways?

Part elevator and part tram, cylindrical cabins take visitors to the top utilizing mechanical and electrical sensors to self-level, similarly to Ferris Wheel gondolas. Designed by Richard Bowser the trams feature five passenger capsules and opened for operation on the North side in 1967, and the South in 1968. In the base of the Arch, passengers enter cabins hanging from an overhead track which rotate 155 degrees during the ascent, thus when passengers arrive at the observation area the track lies beneath their feet. For all the feats of engineering and technology, some parts of the design process will always be the result of serendipity.

In 1960, Saarinen’s firm was searching for an engineer capable of designing the radical transportation system, and happened to call the Montgomery Elevator Office where one of Bowser’s friends worked. Although Bowser lacked a college degree, he had significant experience with elevator design, having already developed with his father a system capable of moving vertically, horizontally and diagonally. Knowing Bowser’s skill set could met Saarinen’s challenging proposal, the friend immediately placed the two in contact. While great designs demand ingenuity and technological innovation, ultimately all successful projects rely on the ability to understand needs and cultivate relationships.

Hanging from the tram track, cabins emerge in the base of the Arch.