# Gateway Arch: Difference between revisions

Location Gateway arch U.S. National Register of Historic Places U.S. National Historic Landmark The Gateway Arch in April 2010. Missouri 62.165 acres (251,570 m2)[1] constructed 1963-1965 design created 1947 Eero Saarinen 87001423 May 28, 1987[2] May 28, 1987[3]

The Gateway Arch, also known as the Gateway to the West, is part of the Jefferson National Expansion Memorial in St. Louis, Missouri. It is 630 feet (192 metres) wide at its base and stands 630 feet (192 metres) tall, making it the tallest man-made monument in the United States,[3] and the tallest accessible structure in the state.

It was designed by architect Eero Saarinen and structural engineer Hannskarl Bandel in 1947. Construction started on February 12, 1963, and ended on October 28, 1965,[4] costing $13 million ($98,797,254 today[5]).[6] The monument opened to the public on July 10, 1967.[7] The Gateway Arch is an architectural marvel because it is designed as a weighted or flattened Catenary arch, which has never been attempted on such a large scale before this project.[3]

Built as a monument to the westward expansion of the United States, the Arch has become the iconic image of St. Louis.

## Physical description

Welds on the Arch's skin seal gaps between 4-by-8-foot sheets of stainless steel. Graffiti is scratched on the lower five to seven feet of the monument.

The design of the Arch was chosen in a national architectural competition in 1947 from among 147 entries. The competition was coordinated by architect George Howe, and the seven jury members included Fiske Kimball, Richard Neutra, Roland Wank, and William Wurster. After narrowing the field, the jury picked Saarinen's design unanimously.[8]

The cross-sections of its legs are isoceles triangles, narrowing from 54 by 52 feet (16 by 16 metres) per side at the base to 17 feet (5.2 metres) at the top. Each wall consists of a stainless steel skin covering a sandwich of two carbon steel walls with reinforced concrete in the middle from ground level to 300 feet (91 metres), with carbon steel and rebar from 300 feet (91 metres) to the peak.[9] The Arch is hollow to accommodate a unique tram system that brings visitors to an observation deck at the top. The interior also contains two sets of emergency stairs (one in each leg), each comprising over 1,076 steps for use in emergencies.[10]

The arch has 60 foot deep foundations below each leg, making it earthquake proof as well as resistant to high speed winds. The arch was designed sway up to 18" in either direction in winds up to 150 mph. The arch weighs 43,000 tons of which 900 tons are the stainless steel panels that cover the entire exterior facade of the arch. [11]

The base of each leg at ground level has an engineering tolerance of one-64th of an inch (0.40 mm) or the two legs would not meet at the top.[4] The legs were built simultaneously. When the time came to connect the legs at the apex, thermal expansion of the sunward-facing south leg prevented it from aligning with the north leg. The St. Louis Fire Department sprayed the south leg with water from firehoses, cooling it until it lined up with the north leg.

A time capsule containing the signatures of 762,000 St. Louis area students was welded into the keystone before the final piece was set in place.[12]

### Tram

The tram is an egg-shaped "elevator". It is operated by the quasi-governmental Bi-State Development Agency under an agreement with the NPS (National Park Service).

From the visitor center, one may move to either base (one on the north end and the other on the south end) of the Arch and enter the tramway. This is very similar to entering an ordinary elevator, through narrow double doors. The north queue area includes displays that interpret the design and construction of the Gateway Arch; the south queue area includes displays about the St. Louis riverfront during the mid-19th century.

Passing through the doors, passengers in groups of five enter an egg-shaped compartment containing five seats and a flat floor. Because of the car shape, the compartments have sloped ceilings low enough to force taller riders to lean forward while seated (for this reason it's recommended that the tallest of the five passengers in the car sit in the center seat facing the door). Eight compartments are linked to form a train, meaning that both trains have a capacity of 40, and that 80 people can be transported at one time. These compartments rotate 5 degrees as they travel, keeping them upright while the entire train follows curved tracks up one leg of the arch. The trip to the top takes four minutes, and the trip down takes three minutes. The car doors have narrow windows, allowing passengers to see the interior stairways and structure of the Arch during the trip.

### Observation area

Near the top of the arch, the rider exits the tram compartment and climbs a slight grade to enter the arched observation area. Thirty-two windows (16 per side) measuring 7 by 27 inches (180 by 690 millimetres) allow views across the Mississippi River and southern Illinois with its prominent Mississippian culture mounds to the east at Cahokia Mounds, and the City of St. Louis and St. Louis County to the west beyond the city.[13] On a clear day, one can see up to 30 miles (48 km).[14]

## Tourism

The Gateway Arch is one of the most visited tourist attractions in the world as well as being on the register of National Monuments for the United States. [3] The Arch attracts more than 4 million visitors every year. [15]

## Mathematics of the Arch

Curvature detail with the windows of the observation deck located around the apex of the arch.

The geometric form of the Arch was set by mathematical equations provided to Saarinen by Dr. Hannskarl Bandel. Bruce Detmers and other architects expressed the geometric form in blueprints with this equation:[16]

${\displaystyle y=A\left(\cosh {\frac {Cx}{L}}-1\right)\quad \Leftrightarrow \quad x={\frac {L}{C}}\cosh ^{-1}\left(1+{\frac {y}{A}}\right)}$,

with the constants

${\displaystyle A={\frac {f_{c}}{Q_{b}/Q_{t}-1}}=68.7672}$

${\displaystyle C=\cosh ^{-1}{\frac {Q_{b}}{Q_{t}}}=3.0022}$

where fc = 625.0925 ft (191 m) is the maximum height of centroid, Qb = 1,262.6651 sq ft (117 m2) is the maximum cross sectional area of arch at base, Qt= 125.1406 sq ft (12 m2) is the minimum cross sectional area of arch at top, and L = 299.2239 ft (91 m) is the half width of centroid at the base.

This hyperbolic cosine function describes the shape of a catenary. A chain that supports only its own weight forms a catenary; in this configuration, the chain is strictly in tension.[17][18] An inverted catenary arch that supports only its own weight is strictly in compression, with no shear. The gateway arch itself is not a catenary, but a more general curve called a flattened catenary of the form y=Acosh(Bx);[19] a catenary is the special case when AB=1. While a catenary is the ideal shape for an arch of constant thickness, the gateway arch does not have constant thickness as it is narrower near the top.

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## References

1. ^ Laura Soullière Harrison (1985). "National Register of Historic Places Inventory-Nomination: Jefferson National Expansion Memorial Gateway Arch / Gateway Arch; or "The Arch"" (PDF). National Park Service. Retrieved 2009-06-21. and Template:PDFlink
2. ^ "National Register Information System". National Register of Historic Places. National Park Service. 2008-04-15.
3. ^ a b c d "Gateway Arch". National Historic Landmark summary listing. National Park Service. Retrieved 2008-07-22. Cite error: Invalid <ref> tag; name "nhlsum" defined multiple times with different content (see the help page). Cite error: Invalid <ref> tag; name "nhlsum" defined multiple times with different content (see the help page).
4. ^ a b Gateway Arch Facts
5. ^ Federal Reserve Bank of Minneapolis Community Development Project. "Consumer Price Index (estimate) 1800–". Federal Reserve Bank of Minneapolis. Retrieved January 2, 2017.
6. ^ http://www.nps.gov/jeff/planyourvisit/arch-faq.htm
7. ^ Arch Timeline