|Chicago River Bascule Bridges, Spanning Chicago River & its north & south branches, Chicago, Cook County, IL HAER ILL, 16-CHIG, 137-6. Larger reference image (JPEG - 150K bytes)Highest resolution image (TIFF - 19739K bytes).|
The records in HABS/HAER were created for the U.S. Government and are considered to be in the public domain. the Library of Congress is not aware of any U.S. copyright protection
Survey number HAER IL-111. Unprocessed field note material exists for this structure (N642). Building/structure dates: 1900 initial construction. Significance: The development of the Chicago trunnion bascule bridge occurred during the first three decades of the twentieth century. Despite the controversy over patent infringement -- Joseph E. Strauss charged the City of Chicago engineers with infringing on his patented Strauss-Trunion bascule bridge -- the Chicago bascule received great acclaim within the civil engineering profession.
Between 1865 and 1890, the City of Chicago built 55 movable highway bridges over waterways within municipal limits. All were center-pier swing spans. Despite its ubiquity, the swing span was not universally admired. Its critics pointed to the fact that the center-pier design was becoming a navigational hazard for the ever-larger vessels of the late nineteenth century.
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The Sears Tower is a skyscraper in Chicago, Illinois. It has been the tallest building in the United States since 1973, surpassing the World Trade Center, which itself had surpassed the Empire State Building only a year earlier. Commissioned by Sears, Roebuck and Company, it was designed by chief architect Bruce Graham and structural engineers Srinivasa and Fazlur Khan of Skidmore, Owings and Merrill.
Construction commenced in August 1970 and the building reached its originally anticipated maximum height on May 3, 1973. When completed, the Sears Tower had overtaken the roof of the World Trade Center in New York City as the world's tallest building. The tower has 108 stories as counted by standard methods, though the building owners count the main roof as 109 and the mechanical penthouse roof as 110. The distance to the roof is 442 m (1,450 ft 7 in), measured from the east entrance.
In February 1982, two television antennas were added to the structure, increasing its total height to 520 m (1,705 ft). The western antenna was later extended to 527 m (1,730 ft) on June 5, 2000 to improve reception of local NBC station WMAQ-TV.
Black bands appear on the tower around the 29th–33rd, 64th–66th, 88th–90th, and 104th–109th floors. These are louvers which allow ventilation for service equipment and obscure the structure's belt trusses which Sears Roebuck did not want to be visible as on the John Hancock Center. The Sears Tower has the second most total floor space of any building in the United States, only behind The Pentagon.
The building's official address is 233 South Wacker Drive, Chicago, Illinois 60606.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article, Sears Tower
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