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Impact and 0 and 7 and Inch and Diameter and Strands.
| 题名： | Impact and 0 and 7 and Inch and Diameter and Strands. |
| 作者： | G. Morcous; K. Hanna; M. K. Tadros; |
| 关键词： | bridge design, concrete, prestressed girders, shear capacity, development length |
| 摘要： | 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. |
| 总页数： | 203p |
| 报告类型： | 科技报告 |
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