Bond Behavior of 15.2-mm (0.6-INCH) Diameter Prestreesing Strands In San Angelo Bridge Research Beams

The objective of this research was to determine the transfer and development lengths for fully bonded, 15.2 mm (0.6 in.) diameter strand on a 51 mm (2 in.) grid in full-size, I-shaped concrete beams. Two Texas Type C beams were fabricated with high-strength concrete and two were fabricated with normal-strength concrete. The high-strength and normal-strength concrete had 56-day and 28-day compressive strengths of approximately 90 MPa (13,000 psi) and 48 MPa (7000 psi), respectively. The laboratory research beams were intended to have characteristics similar to the AASHTO Type IV beams of a bridge under design, and now completed, in San Angelo, Texas. Also, to assess the surface condition of the strand and its effect on bond, pull-out tests were performed on strand samples embedded in concrete blocks.

Results from transfer and development length tests performed on the laboratory research beams were compared with values predicted by equations from the American Concrete Institute code and the American Association of State Highway Transportation Officials specifications. Results also were compared with values predicted by equations proposed by other researchers.