Construction of the Arch

By Johnny Moler

The Jefferson National Expansion Memorial built on the banks of the Mississippi River in St. Louis, Missouri is a marvelous tribute to the growth of the United States. The monument is more than large enough to symblize the greatness of America. At a cost of nearly a million dollars and 40 city blocks, the project was completed. Inside the Memorial is the well know Arch designed by Eero Saarinen.

For the foundation, reinforced concrete was sunk 60ft into the ground 30 of which is in bedrock, helping give the arch its excellent structural strength. 252 alloy-steel tensioning bars per leg were extended 34 ft. deep into the foundation to secure the monument to the base. These bars are 1-3/4" in diameter and made of alloy steel with an ultimate strength of 145 ksi. They were attached into the equilateral triangle legs of the Arch.

Next, the foundation was prestressed to 18,000 tons of pressure per leg with a hydraulic jack. Each Arch leg is double walled with a 40 ft. wide core tapering to 15-1/2 ft. at the top. The inside skin is A-7 carbon steel, 3/8 in. thick and the outer skin is made from 900 tons of polished stainless steel. The stainless steel panels were MIG welded with a mixture of 75% argon and 25% carbon on the polished side. The welds were tested and the stainless steel was cleaned because halos formed from the heat from welding.

The structure is made of sections and were placed onto the base with cranes. A creeper crane would lift the completed section from the welding pad into their place. Then the sections would be fastened together using 35-ton jack screws. Above 72 ft., creeper derricks pulled the 12 ft. high, 50 ton sections into place. To support the creeper derricks above 530 ft., a stabilizing truss was made. This was used to keep the two individual legs from falling.

After the truss was built, 21 more section were put into place. Once the final section was put into place the creeper derricks helped let the truss down and then slowly creeped down the legs assembling themselves as they went. The Arch was built so strong that if subjected to a 150 mph wind it would only deflect at most 18 in. at the top of the Arch.

Eero Saarinen


By Shane Thomas

Eero Saarinen is one of the most renowned Architects of the twentieth century. Saarinen's most famous work other than the Arch is the General Motors Technical Center in Detroit, MI, Dulles International Airport in Washington D.C. and TWA Terminal in New York City, NY.

His architectural background began when he was a boy. Having been around his parents, Eliel Saarinen (his father - a successful Architect) and Loja Saarinen (his mother - an architectural model maker), he gained the basic knowledge for architectural design and construction. At age 12, Eero won his first award for a matchstick design. Later, he would win several contests and awards for his talented designs.

He worked with his father in an architectural firm in Cranbrook, Michigan for several years after studying in Europe. At age 37, Saarinen finally got his big break when his project, for the Jefferson National Expansion Memorial, was selected.

The St. Louis Arch, completed after Saarinen's death in 1961, is by far his most notorious design - a powerful and long lasting memorial to commemorate the westward expansion of the United States in the 19th century.