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

摘要

style="text-align: left;">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. >References style="text-align: left;">1. AASHTO, AASHTO LRFD Bridge Design Specifications, American Association of State Highway and Transportation Officials, Washington, DC, 1994. style="text-align: left;">2. Collins, M. P., and Mitchell, D., Prestressed Concrete Structures, Prentice Hall, New York, NY, 1991, pp. 343-374. style="text-align: left;">3. Vecchio, F. J., and Collins, M. P., target="_blank" title="a€?The Modified Compression Field Theory for Reinforced Concrete Elements Subjected to Shear,a€?" href=" http://dx.doi.org/10.14359/10416 ">a€?The Modified Compression Field Theory for Reinforced Concrete Elements Subjected to Shear,a€? ACI Journal, V. 83, No. 2, March-April 1986,  pp. 219-231. style="text-align: left;">4. Vecchio, F. J., and Collins, M. P., target="_blank" title="a€?Predicting the Response of Reinforced Concrete Beams Subjected to Shear Using Modified Compression Field Theory,a€?" href="http://dx.doi.org/10.14359/2515 ">a€?Predicting the Response of Reinforced Concrete Beams Subjected to Shear Using Modified Compression Field Theory,a€? ACI Structural Journal, V. 85, No. 3,  May-June 1988, pp. 258- 268. style="text-align: left;">5. Shahawy, M., and Cai, C. S., target="_blank" title="a€?Enhancement of the Performance of Prestressed Concrete Girders Using Strand Anchorage,a€?" href=" http://dx.doi.org/10.15554/pcij.09012001.82.96 ">a€?Enhancement of the Performance of Prestressed Concrete Girders Using Strand Anchorage,a€? PCI JOURNAL,  V. 46, No. 5, September-October 2001, pp. 82-96. style="text-align: left;">6. Ma, Z., Tadros, M. K., and Baishya, M., target="_blank" title="a€?Shear Behavior of Pretensioned High-Strength Concrete Bridge I-Girders,a€?" href=" http://dx.doi.org/10.14359/848 ">a€?Shear Behavior of Pretensioned High-Strength Concrete Bridge I-Girders,a€? ACI Structural Journal, V. 97, No. 1, January-February 2000, pp. 185-192. style="text-align: left;">7. Noppakunwijai, P., Jongpitakseel, N., Ma, Z., Yehia, S. A., and Tadros, M.  K., target="_blank" title="a€?Pullout Capacity of Non-Prestressed Bent Strands for Prestressed Concrete Girders,a€? " href="http://dx.doi.org/10.15554/pcij.07012002.90.103 ">a€?Pullout Capacity of Non-Prestressed Bent Strands for Prestressed Concrete Girders,a€? PCI JOURNAL, V. 47, No. 4,  July-August 2002, pp. 90- 103. style="text-align: left;">8. Tan, K. H., and Naaman, A. E., target="_blank" title="a€?Strutand Tie Model for Externally Prestressed Concrete Beams,a€?" href=" http://dx.doi.org/10.14359/4492 ">a€?Strutand Tie Model for Externally Prestressed Concrete Beams,a€? ACI Structural Journal, V. 90, No. 6, November-December 1993, pp. 683-691. style="text-align: left;">9. Rami