Gateway Arch

Infobox_nrhp2 | name =Gateway Arch
nhl=yes

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caption =
location= Memorial Drive, St. Louis, Missouri, USA
lat_degrees = 38
lat_minutes = 37
lat_seconds = 31
lat_direction = N
long_degrees = 90
long_minutes = 11
long_seconds = 0
long_direction = W
locmapin = Missouri
area =62.165 acres
built = constructed 1963-1965
design created 1947
architect= Eero Saarinen
architecture=
added = May 28, 1987cite web|url=http://www.nr.nps.gov/|title=National Register Information System|date=2008-04-15|work=National Register of Historic Places|publisher=National Park Service]
designated_nhl = May 28, 1987cite web|url=http://tps.cr.nps.gov/nhl/detail.cfm?ResourceId=2017&ResourceType=Structure
title=Gateway Arch |accessdate=2008-07-22|work=National Historic Landmark summary listing|publisher=National Park Service]
governing_body = National Park Service
refnum=87001423

The Gateway Arch, also known as the Gateway to the West, is an integral part of the Jefferson National Expansion Memorial and the iconic image of St. Louis, Missouri. It was designed by Finnish-American architect Eero Saarinen and structural engineer Hannskarl Bandel in 1947. It stands 630 feet (192 m) tall, and is 630 feet (192 m) wide at its base, making it the tallest monument in the United States. Construction of the arch started on February 12, 1963 and was completed on October 28, 1965. The monument opened to the public on July 24, 1967.

Physical Description

The cross-sections of its legs are equilateral triangles, narrowing from 54 feet (16.5 m) per side at the base to 17 feet (5.2 m) at the top. Each wall consists of a stainless steel skin covering reinforced concrete from ground level to 300 feet (91 m), with carbon steel and rebar from 300 feet (91 m) to the peak. The interior of the Arch is hollow and contains a unique transport system leading to an observation deck at the top. The interior of the Arch also contains two emergency stairwells of 1076 steps each, in the event of a need to evacuate the Arch or if a problem develops with the .

The base of each leg at ground level had an engineering tolerance of one sixty-fourth of an inch or the two legs would not meet at the top.

During construction, both legs were built up simultaneously. When the time came to connect both legs together at the apex, thermal expansion of the sunward facing south leg prevented it from aligning precisely with the north leg. This alignment problem was solved when the Saint Louis City Fire Department sprayed the south leg with water from firehoses until it had cooled to the point where it aligned with the north leg.

It is the tallest habitable structure in St. Louis (taller than One Metropolitan Square, the tallest building), and the second tallest in Missouri (behind One Kansas City Place in Kansas City)).

Tram

Eero Saarinen died from a brain tumor four years before the Arch was completed; prior to his death he had decided to incorporate a power lift system to obviate the need to climb the 1000-plus stairs. But the shape of the arch would have made a standard elevator impossible. After approaching several elevator companies who failed to come up with a viable method, Saarinen hired parking-lot elevator designer Richard Bowser to do the job. Skeptical city leaders gave Bowser only two weeks to submit a design, but he succeeded. By 1968 a unique tram system that combined an elevator cable lift system with gimbaled cars functionally similar to ferris wheel gondolas had been installed.

The tram is operated by the quasi-governmental Bi-State Development Agency under an agreement with the NPS.

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 much as one would enter an ordinary elevator, through narrow double doors. The north queue area includes displays which 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 individually retain an appropriate level by periodically rotating every 5 degrees, which allows them to maintain the correct orientation while the entire train follows curved tracks up one leg of the arch. The trip to the top of the Arch 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 compartment and climbs a slight grade to enter the arched observation area. Small windows, almost invisible from the ground, 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 Saint Louis and St. Louis County to the west beyond the city. On a clear day, one can see up to thirty miles (48 km).

Mathematics 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: $y=A\; left\; (\; cosh\; frac\; \{x\}\{L\}\; C-\; 1\; ight\; ),$ or, equivalently $x=frac\; \{L\}\{C\}\; cosh^\{-1\}\; left\; (\; 1+\; frac\; \{y\}\{A\}\; ight\; ),$ where $A\; =\; frac\; \{f\_c\}\{frac\{Q\_b\}\{Q\_t\}-1\}\; =\; 68.7672$ $C\; =\; cosh^\{-1\}\; frac\; \{Q\_b\}\{Q\_t\}\; =\; 3.0022$ $f\_c\; =\; mbox\{maximum\; height\; of\; centroid\; (in\; feet)\}\; =\; 625.0925$ $Q\_b\; =\; mbox\{maximum\; cross\; sectional\; area\; of\; arch\; at\; base\; (in\; sq.\; feet)\}\; =\; 1262.6651$ $Q\_t\; =\; mbox\{minimum\; cross\; sectional\; area\; of\; arch\; at\; top\; (in\; sq.\; feet)\}\; =\; 125.1406$ $L\; =\; mbox\{half\; width\; of\; centroid\; at\; the\; base\; (in\; feet)\}\; =\; 299.2239$