Measurement of Transfer Length on Prestressing Strands in Prestressed ConcreteSpecimens

摘要

Recent studies had indicated that current AASHTO provisions for the transferlength and development length of 0.6-inch prestressing strand were unconservative. On the basis of very limited data, restrictions on 0.6-inch strand were adopted as an interim measure until additional research results were available to either substantiate or restructure code provisions. In response to the research need, the report focuses on determining the transfer length of 0.5-inch and 0.6-inch strand. Sixty-two (62) transfer length specimens were cast and tested. Of these, 26 were single-strand specimens. Eighteen were three-strand specimens, and six were five-strand specimens. Fifty specimens had rectangular cross sections with concentric prestressing. The remaining twelve sections were I-shaped, designed to resemble the cross section for an AASHTO girder. Research variables included the number of strands, strand spacing (2-inch or 2.25-inch), strand diameter (0.5-inch or 0.6-inch), and the effects of transverse reinforcement. The transfer length of debonded strand was also studied. Overall, test results indicated that the behavior of 0.6-inch strand is very similar to the behavior of the 0.5-inch strand.