St Louis Gateway Arch

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St Louis Gateway Arch

Gateway Arch reflects St. Louis’ role in the Westward Expansion of the United States during the nineteenth century. It was Thomas Jefferson who bought the Louisiana Territory in the Louisiana Purchase and made Westward Expansion possible.

Jefferson National Expansion Memorial consists of the Gateway Arch, the Museum of Westward Expansion, and St. Louis’ Old Courthouse. The park is a memorial to Thomas Jefferson’s role in opening the West, to the pioneers who helped shape its history, and to Dred Scott who sued for his freedom in the Old Courthouse.

The Arch is a catenary curve. Catenary means it is the shape a free-hanging chain takes when held at both ends. More specifically, a catenary curve is the shape assumed by a rope or chain of uniform density suspended from two points and acted upon solely by the forces of gravity.

Gateway Arch (podcast 2:00) – stainless steel – a material that would represent the modern age. This metal was first created in the 19th century, but perfected in the 20th. It is composed of steel (a combination of iron and carbon) with a dash of chromium. The mix of iron and carbon gives the metal strength, but chromium provides longevity by overcoming iron’s weakness of rusting.

An impressive structure that is graceful and strong

The Gateway Arch made out of steel and concrete. Double wall construction with 1/4” stainless steel on the outside and 3/8” structural steel inside. The distance between the wall or “skins” at the surface is 3 feet, narrowing to less than 1 foot at the top. There is a layer of concrete between the skins approximately half way up the legs of the Gateway Arch.

The architect, Eero Saarinen won a national competition and the prize of designing the memorial in 1947. Designing and constructing the Gateway Arch followed the steps in the [/Engineering%20Design%20Process Engineering Design Process]. The Gateway Arch project started in February 1963 and the last piece put into place October 28, 1965. The north leg was completed first and opened in July 1967 and the south leg opened in May 1968.

  • Ask – A competition was held in 1947 for the design of the Jefferson National Expansion Memorial that was to include “a large, central feature.” What were the requirements for the monument design? What was special about the site to be developed?
  • Imagine – The designers wanted to make a structure that symbolized the gateway to the West and the expansion of the pioneers in America. Stainless steel can support a tall structure that would be impressive and graceful for a reasonable cost. Architect, Eero Saarinen used a mathematical equation to create the catenary curve shape of the Arch. What are the special properties of a cantenary? What makes this structural form suitable for the St. Louis Arch? What materials were available?
  • Plan – The Gateway Arch is 630 feet tall, and the span is 630 feet wide at ground level between the outer sides of the legs. The legs are 54 feet wide at the base. The foundation is 60 feet deep. The first of the 142 stainless steel sections of the Gateway Arch was placed on October 28, 1965. What is special about the shape of the St. Louis Arch? How was it built?
  • Create – The windows at the top are 7” x 27” – 16 windows on each side of the observation deck. Over 500 tons of pressure was used to jack the north and south legs of the Arch apart for the last four-foot piece to be placed at the top. A larger window would not withstand that pressure. During the arch construction, how were the windows installed?
  • Improve – The tram / elevator system was added once the arch design was decided. In designing a conveyance system for the Arch, there were very few criteria to meet except that the National Park Service had established a passenger volume of 3,500 people in an 8-hour day, or up to 11,000 people in a 14-hour day, as visitors to the Arch. It was also required that in no way could the conveyance system distort the exterior of the Arch. Since the St. Louis arch was built, what changes have been made?

That’s engineering

  • stainless steel – a steel alloy with a minimum of 10.5 or 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel. There are over 150 grades of stainless steel, of which fifteen are the most used.

Engineering ideas

  • forces, cantenary, stainless steel, alloy, corrosion, chromium, trapezoid

Do it
Here are some challenges for you to work on…

  • Max Axiom Arch – make this arch with foam trapezoid shapes
  • Find other examples of arch bridges and structures – catenary, corbel, aquaduct, tied arch

Learn more…

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