Monitoring of the 205-ft long Pretensioned Precast Super Girders of the Alaskan Way Viaduct, Seattle, WA


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Title: Monitoring of the 205-ft long Pretensioned Precast Super Girders of the Alaskan Way Viaduct, Seattle, WA

Author(s): S.S. Badie, D. Chapman, A. Mizumori, Y. Jiang, S.J. Seguirant, and B. Khaleghi

Publication: Special Publication

Volume: 304


Appears on pages(s): 41-52


Date: 10/27/2015

The Alaskan Way Viaduct replacement project is a joint program between the Washington State Department of Transportation (WSDOT), the Federal Highway Administration (FHWA), the City of Seattle, King County and the Port of Seattle. The project consists of several sub-tasks including the total replacement of the State Route 99 double-deck viaduct. The Alaskan Way Viaduct is a vital factor for economic sustainability while serving as a major transportation artery for the greater Seattle metropolitan area. Span 2C of this project is 210-ft (64.01 m) long and consists of an 8-inch (203 mm) thick cast-in-place concrete slab supported on seventeen WF100G precast pretensioned concrete girders. Construction is split into two phases: Phase I includes eight girders spaced at 6 ft-5 inches (1.96 m) on center and Phase II includes nine girders spaced at 6 ft (1.83 m) on center. This span has an eleven-degree skew and includes four cast-in-place concrete diaphragms at quarter points in addition to the end diaphragms. The WF100G girders are each 205-ft (62.48 m) long and 100-inch (2540 mm) deep. Each girder is reinforced with eighty (80) 0.6-in. (15.24 mm) diameter, 270 ksi (1860 MPa), low-relaxation seven-wire strands. WSDOT in collaboration with Concrete Technology Corporation (CTC) and the George Washington University (GW) have instrumented four girders of the second phase with about forty (40) vibrating wire gauges. This paper presents the details of the on-going plan developed by the WSDOT/CTC/GW team to monitor the progress of prestress losses over a period of three years. The paper will also present the challenges that the team faced during the instrumentation stage.