Development device for prestressing strands in beams

A grouted sleeve device for gripping prestressing steel, developed and tested in previous research by Potter 2009, was embedded into the end regions of prestressed concrete bridge beams in an attempt to anchor the terminal ends of the strands. The goal was to produce enough bond strength in the device to effectively act as a strand anchor and reduce the development length of the strand. Anchored strand could also serve to increase ductility, improve ultimate capacity and reduce the number of stirrups required in the end region.;Four test series were performed, each focusing on separate aspects of the research. Test Series 1 focused on prestress release testing using 0.6-in.-diameter prestressing strand with different steel sleeve sizes and grout types; the results of these tests were used to finalize the anchorage device design. Series 2 incorporated two different designs into the fabrication of two half-scale AASHTO Type II prestressed concrete beams. These beams were fitted with strain gauges for monitoring the transfer length during detensioning. In Series 3, the beams from the previous test series were tested in a shear test configuration to failure, and results were compared to a control specimen. For Series 4, unstressed pull-out specimens were created to test the bond performance of the second anchorage type embedded in a beam of Series 2 and 3.;Finalization of device design and field installation method in Test Series 1 provided a path for the research to take. The transfer length testing that followed established that reducing the transfer length (Lt) in a prestressed beam by means of an embedded anchor was possible. Improvement of the transfer length due to the grouted device is considered negligible after accounting for concrete strength, but the second anchor type (coil confinement) showed a reduction in Lt of 30%. Both types of embedded anchors showed an improvement in ductility and ultimate capacity, but proper end region detailing using shear steel would be beneficial in future tests to more thoroughly test the performance of the anchor.