Reliability of Transfer Length Estimation from Strand End Slip

The force in a prestressing strand is transferred by bond to
the concrete in the release operation. At this stage, strand
stress varies from zero at the free end of the member to a
maximum value (effective stress). Transfer length is defined
as the distance required to develop the effective stress in the
prestressing strand.
1 Variation in strand stress along the
transfer length involves slip between the strand and the
concrete. The measurement of the strand end slip is an indirect
method to determine the transfer length.
2 Most experimental
standards 3-6
are based on this method, and it has been proposed
as a simple nondestructive assurance procedure by which the
quality of bond can be monitored within precasting plants.7
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