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原文传递 THE TIES THAT BIND: THE 10-YEAR FIGHT FOR 0.6-INCH DIAMETER STRANDS.

题名：	THE TIES THAT BIND: THE 10-YEAR FIGHT FOR 0.6-INCH DIAMETER STRANDS.
作者：	Lane-S; Rekenthaler-D Jr.
关键词：	HIGH-PERFORMANCE; REINFORCED-CONCRETE; STEEL-FIBERS; PRESTRESSING-STRANDS; SPACING-; FEDERAL-HIGHWAY-ADMINISTRATION; BONDING-STRENGTH; SPECIFICATIONS-; SAFETY-; PRESTRESSED-CONCRETE-BEAMS
摘要：	In 1988, steel strand manufacturers were interested in bumping the 0.5-in (12.7-mm) diameter threshold to 0.6 in (15.24 mm) to increase structural durability and strength. Although the prestressed strands were to be a boon to structural engineers, the growing prominence of improved construction materials, such as high-performance concrete that requires an equally powerful strand, forced manufacturers to consider even stronger strands. In conjunction with their 0.6-in (15.24-mm) proposal, manufacturers also wanted to maintain the minimum spacing between the strands at 2 in (60.96 mm) and break with the requirement that strand spacing be four times the strand diameter. This represented a significant increase in the load transferred to the concrete part of the beam and was a safety issue. However, to add an additional 0.4 in (10.16 mm) to the spacing requirement would force manufacturers to completely retool their prestressing operations to accommodate the new spacing requirements, and this was prohibitively expensive. In October 1988, the Federal Highway Administration (FHWA) Bridge Division issued a memorandum that forbade the use of 0.6-in strands or changing the strand spacing requirement until additional studies were carried out to determine their safety. In addition, the FHWA ruled that a 1.6 multiplier be added to the bonding equation as a safety factor. The memorandum created quite an uproar across the country. In addition to research by the FHWA, a dozen studies were launched at colleges and institutes to address these issues. In May 1996, the FHWA released a memorandum announcing that 0.6-in-diameter strands were acceptable. The agency also stated that 2-in spacing for 0.6-in-diameter strands was acceptable and that designers could use 0.5-in-diameter strands at 1.75-in (44.45-mm) spacing if they wanted. One year later, members of the American Association of State Highway and Transportation Officials passed by voice vote the allowance for these new specifications.
总页数：	Public Roads. 1998/03. 61(5) pp27-29 (5 Phot.)
报告类型：	科技报告