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Accession Number PB2013-100414
Title Impact and 0 and 7 and Inch and Diameter and Strands.
Publication Date Jun 2011
Media Count 203p
Personal Author G. Morcous K. Hanna M. K. Tadros
Abstract Since the Federal Highway Administration (FHW A) allowed the use of 0.6 in. (15.2 mm) diameter strands at 2 in. (51 mm) minimum spacing in 1996, they have been increasingly used in the production of pretensioned concrete bridge girders. For several years, 0.7 in. (17.8 mm) diameter strands have been successfully used in cable bridges and for mining applications. Using these large diameter strands in pretensioned concrete girders at 2 in. (51 mm) spacing will result in approximately 350/0 increase in the prestressing force compared to the same number of 0.6 in. (15.2 mm) diameter strands, which will, consequently, allow for longer spans, shallower structural depth, and/or wider girder spacing. For the same prestressing force, using 0.7 in. (17.8 mm) diameter strands results in fewer strands to jack and release, fewer chucks, and higher flexural capacity due to lowering the center of gravity of the strands. In this report, the design and production challenges of using 0.7 in. (17.8 mm) diameter strands in pretensioned concrete bridge girders are discussed. Several experimental investigations were carried out to determine the mechanical properties of 0.7 in. (17.8 mm) diameter strands, address production concerns, and evaluate transfer length, development length, and end zone cracking associated with using such large diameter strands in pretensioned members. Specimens included pretensioned rectangular prisms, 24 in. deep T -girders, NU900, and NUIIOO girders. Positive production experience and predictable test results indicated that 0.7 in. (17.8 mm) diameter strands can be used with no major changes to the current production practices and/or design criteria according to the current AASHTO LRFD specifications.
Keywords Bridge design
Bridge girders
Bridges
Concrete
Development length
Prestressed girders
Shear capacity


 
Source Agency Federal Highway Administration
NTIS Subject Category 50A - Highway Engineering
85H - Road Transportation
91B - Transportation & Traffic Planning
Corporate Author Nebraska Univ., Lincoln.
Document Type Technical report
Title Note Final rept.
NTIS Issue Number 1302
Contract Number N/A

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