Gateway Arch National Park commemorates President Jefferson’s vision of a continental nation, the individuals and cultural groups who helped shape its history, and St. Louis’ role in westward expansion. The original park’s name, “Jefferson National Expansion Memorial,” came on December 21, 1935, honoring President Thomas Jefferson. His acquisition in 1803 of the Louisiana Territory from France, known as the Louisiana Purchase, doubled the size of the United States. (The introductory information in the first 3 paragraphs of this post is from the National Park’s website and its FAQs.) The first part of this post gives us a look at the Arch. The last half details what it took to build the Arch.
St. Louis and the Gateway Arch are both referred to as the “Gateway to the West.” The arch is an inspirational symbol of Thomas Jefferson’s vision of building a unified continental nation and St. Louis’ role as a confluence [of 2 rivers] and gateway to the American West during the 19th century. It was designated a National Historic Landmark in 1987, and the bill to rename the arch and its surrounding park grounds as a national park was signed into law in February 2018.
Construction of the Arch began on February 12, 1963, and was completed on October 28, 1965. The Arch is designed to sway only as much as 18 inches in 150-mile per hour winds, and it can withstand an earthquake; however, under normal weather conditions, the Arch does not sway at all. It takes a 50-mile an hour wind to move the top 1-1/2 inches each side of center.
views from the top
Each tram consists of 8 capsules (or tram cars) that have clear doors on the front and are closed on the back. Each tram car has a 5-foot diameter, and there are 5 seats in each car.
We decided to stay on the ground.
the Arch’s designer and other information
The designer of the Arch, Eero Saarinen, came from Finland and was one of the most renowned architects of his time. When he entered the 1947 architectural competition for the “Jefferson National Expansion Memorial,” he wanted to design a monument not only to honor Thomas Jefferson and the nation, but also to highlight the modern age.
construction of the Arch
The total building cost of the Arch was $13 million; $11 million was made up of 75% Federal funds and 25% City of St. Louis funds. The remaining $2 million for the Arch transportation system was financed by the Bi-State Development Agency. The ingenious tram ride to the top was designed by Dick Bowser.
The old St. Louis riverfront was selected as the site for a National Monument in 1935 to commemorate the nation’s expansion toward the west. We were told by someone we met that this area was selected since it was starting to deteriorate. The river site had been busy when boats were the main source of transportation on the Missouri River to and from the north (the Dakotas and Canada) and the south (Louisiana and the Gulf Coast.). When railroads took over the bulk of moving products all over the U.S., travel on the Missouri River was no longer needed.
Two main engineering problems confronted the Pittsburgh-Des Moines Steel engineers as they began working on the project in 1960:
- How do you build a 630-foot arch, which like all arches depends on a keystone to stand up? [A keystone piece usually refers to the wedge-shaped stone at the apex of an arch or vault. AI] As the final stone is inserted, it locks all the other pieces into position and allows the entire structure to bear weight
- Can you build 2 curving towers (the legs of the Arch) and keep them from falling inward before you place the keystone?
Some engineers suggested long guy wires stretching huge distances to the north and south of each leg, but the final solution was the use of 1-1/4-inch steel post-tensioning rods embedded in the concrete between the inner and outer skins of the steel.
When the Arch reached 530 feet, an additional stabilizing strut was placed between the legs to ensure their stability until the keystone could be placed.
Now to the orthotropic design issues.
If the Arch had been built in 1948, the walls would have been 3 feet thick from the ground all the way to the top. The tram wouldn’t have been able to be placed inside the legs of the Arch. However, advances in engineering by the late 1950s made the Arch structure possible.
The solution was an orthotropic design [This definition is from AI: a material or structure that has distinct, unique properties (such as strength, stiffness, or elasticity) in three mutually perpendicular directions]. The Arch has no real structural skeleton. Its inner and outer steel skins, joined together, form a composite load bearing structure, giving it its strength and permanence.
Aren’t we glad that the Arch was built in the 1960s!
Now to the Old Courthouse across the street and some information on the Dred Scott decision.
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