Innovative Methods Used in the Design and Construction of the New Tacoma Narrows Bridgeby Jeff A. Lavinder, P.E.,
Thomas Spoth, P.E.,
Document Type: Proceeding Paper
Part of: Structures Congress 2008: Crossing Borders
On September 25, 2002, Notice-to-Proceed for a Design/Build Agreement was issued by the Washington State Department of Transportation (WSDOT), directing Tacoma Narrows Constructors (TNC) to design and construct a new parallel suspension bridge on behalf of the Washington State Department of Transportation. The longest suspension bridge to be built in the United States since New York's Verrazano Narrows Bridge opened in 1964, the new bridge will be the first major suspension bridge in the world to be constructed under a Design/Build contracting arrangement with a fixed price and firm delivery date. The new suspension bridge will consist of a 2,800-ft (854 m) mainspan with side spans of 1400 ft (427 m) and 1200 ft (366 m) respectively. Gravity anchorages located on the hillside of the Narrows resist the tension in the main cables by a combination of base friction and passive resistance of the soil. The anchorages are massive reinforced concrete structures each containing 20,600 cubic yards (15,750 m³) of concrete and 900,000 lbs (408,000 kg) of reinforcing steel. Two- and three-dimensional soil-structure interaction analysis was carried out to determine the stability of the anchorage under cable pull and extreme event seismic loads. A global slope stability analysis was also carried out to evaluate the factor of safety against the failure of the hillside on the shoreward side of each anchorage. Two towers, 510 feet (152.5 m) tall, support the main cables. Three post-tensioned concrete struts brace the two legs of each tower. Tower legs were constructed using the jump form method of construction.
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