Effects of Strand Anchorage Devices on Shear Strength of Pretensioned Concrete Beams

摘要

A series of 12 pretensioned beams were loaded to failure in the laboratory under a concentrated load, placed to produce a shear span with a length-to-depth ratio of 1.5, so as to fail the beam in shear. In an attempt to reduce the prestress transfer length for the strands and increase the shear strength of the beam near the support, anchorage devices were attached to the ends of the prestressing strands before casting. For most beams, these devices were totally encased in concrete during the casting process. These modified beams exhibited no significant increase in shear strength relative to otherwise identical reference beams fabricated without the devices. A final set of beams was fabricated with the anchorage devices bearing externally on the ends -of the beams, and with a deliberate debonding between the strand and concrete near the ends of the beams. These girders exhibited higher failure loads and enhanced ductility, developing a very distinct strut-and-tie mechanism at failure. The study indicated the potential of strand end anchorage to enhance shear capacity in the end regions of pretensioned girders.