style="text-align: left;">Vertical cracks, termed a€?pre-release cracks,a€? beginning at the top flange and propagating downwardinto the section depth have been observed to develop during the production of long-span prestressed concrete bridge girders. The cracking, which is attributed to the restrained shrinkage of the concrete and thermal effects during the curing period prior to release of the prestressing strands, tends to be more critical for long-span girders with deep sections and large amounts of prestressing strands. Studies were conducted at the University of Minnesota to investigate the effects ofpre-release cracks on the behavior of bridge girders. The effects of the size of pre-release cracks on beam stresses and crack-closure behavior were studied with finite element models. Full-scale Mn/DOT Type-28M prestressed concrete bridge girders incorporating artificially-made pre-release cracks were tested under four-point bending to verify the findings. Closing of the pre-release cracks and the beam strains and deflections were monitored continuously during the load tests. The pre-release cracks were found to cause local changes in the beam strains near the crack locations. Beams with pre-release cracks were observed to undergo flexural crack initiation and crack re-opening at lower loads than similar beams without pre-release cracks. >References style="text-align: left;">1. Ahlborn, T., French, C., and Shield, C., a€?High-Strength Prestressed Concrete Bridge Girders,a€? Minnesota Department of Transportation, Research Report MN/RC-2000-32, 2000, St. Paul, MN. style="text-align: left;">2. Roller, J. J., Martin, B. T., Russell, H. G., and Bruce, R. N., target="_blank" title="a€?Performance of Prestressed High Strength Concrete Bridge Girders,a€?" href="http://dx.doi.org/10.15554/pcij.05011993.34.45 ">a€?Performance of Prestressed High Strength Concrete Bridge Girders,a€? PCI JOURNAL, V. 38, No. 3, May-June 1993, pp. 34-45. style="text-align: left;">3. Roller, J. J., Russell, H. G., Bruce, R. N., and Martin, B. T., target="_blank" title="a€?Long-Term Performance of Prestressed, Pretensioned High Strength Concrete Bridge Girders,a€?" href="http://dx.doi.org/10.15554/pcij.11011995.48.59 ">a€?Long-Term Performance of Prestressed, Pretensioned High Strength Concrete Bridge Girders,a€? PCI JOURNAL, V. 46, No. 6, November- December 1995, pp. 48-59. style="text-align: left;">4. Green, J. K., Cookson, P. J., and Johnson, K. A. L., a€?The Performance of Pretensioned Concrete Beams That Have Cracked Before Transfer of Prestress,a€? The Structural Engineer, V. 62B, No. 4, December 1984, pp. 79-85. style="text-align: left;">5. Zia, P., Kowalsky, M. J., Ellen, G. C., and Longo, S. E., a€?Fatigue Testing of Two Full-Size Pre-Cracked AASHTO Bridge Girders,a€? Large-Scale Structural Testing, SP 211, 2003, American Concrete Institute, Farmington Hills, MI, pp. 1-16. style="text-align: left;">6. Zia, P., and Caner, A., a€?Cracking in Large-Sized Long-Span Prestressed Concrete AASHTO Girders,a€? North Carolina Center for Transportation Engineering Studies, Research Report FHWAINC/94-003, 1993, Raleigh, NC. style="text-align: left;">7. Wyffels, T., French, C., and Shield, C., a€?Effects of Pre-Release Cracks in High-Strength Prestressed Girders,a€? Minnesota Department of Transportation, Research Report MN/RC-2000-25, 2000, St. Paul, MN. style="text-align: left;">8. Hibbit, Karisson & Sorensen, Inc., ABAQUS. Version 5.4, Pawtucket, RI, 1994. style="text-align: left;">9. Baran, E., French, C., and Shield, C., a€?Effects of Vertical Pre-Release Cracks on Prestressed Bridge Girders,a€? Minnesota Department of Transportation, Research Report MN/RC-2003-33, 2002, St. Paul, MN. style="text-align: left;">10. Shanafelt, G. 0., and Horn, W. B., a€?Guidelines for Evaluation and Repair
展开▼
