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Field Measurement and Evaluation of Time-Dependent Losses in Prestressed Concrete Bridges
Author(s) and Affiliation(s):
Okey Onyemelukwe and Chris Mills, University of Central Florida, Orlando, Florida Moussa Issa, Florida Department of Transportation Structures Laboratory, Tallahassee, Florida
Principal Investigator:
Okey Onyemelukwe
Florida Department of Transportation
Research Start Date:
August 1995
Expected Completion Date:
August 1998
Research Objectives:
The first phase of the project, involving bridge instrumentation and data collection, was initiated in August 1995. The primary objective is to determine the time-dependent losses in prestressed concrete bridges. The Westbound Gandy Bridge in Tampa, Florida, currently under construction, is instrumented to measure prestress losses. Typical approach span units of the bridge were originally designed as 4-span continuous post-tensioned girders of 144 ft. However, the contractor's value engineering study called for a modified design consisting primarily of 3 simply supported spans with pretensioned girders of 144 ft. The girder used is a modified AASHTO Type VI girder, which is 6 inches deeper than the Florida Bulb-T providing 18% additional area. The girder has a 44% greater moment of inertia and 64% greater ultimate capacity, thus allowing the change from 4-span continuous to 3 simply supported pretensioned spans.
Expected Products or Deliverables:
Design charts and tables accounting for the effect of time-dependent losses in design.

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