Effects of alkali-silica reaction and delayed ettringite formation on anchorage of prestressing strands in trapezoidal box beams with dapped ends

摘要

>Concern about the effects of alkali-silica reaction (ASR) and delayed ettringite formation (DEF) on dapped prestressed concrete trapezoidal box beams in Houston, Tex., prompted an investigation of their shear strength. Beams originally intended for a highway bridge project were stored in a local precast concrete yard and were exposed to the environment for 15 years. During that period, ASR/DEF deterioration of varying severity occurred. Load tests were conducted on five specimens (two of which are discussed in this paper) with varying levels of distress to study the performance of the dapped end and to assess the effect of the ASR/DEF deterioration on the in-service beams. The strength of each specimen was governed by shear-induced anchorage failure confirmed both by the formation of cracks in the development region and slip of the prestressing strands. The length available for the evelopment of the flexural reinforcement was limited, and ASR/ DEF cracking along the development length exacerbated the problem.>References>1. PCI Industry Handbook Committee. 2004. PCI Design Handbook: Precast and Prestressed Concrete. MNL-120. 6th ed. Chicago, IL: PCI.>2. Larson, Nancy A., Oguzhan Bayrak, and James Jirsa. 2010. a€?Structural Performance of ASR/DEF Damaged Prestressed Concrete Trapezoidal Box Beams with Dapped Ends.a€? Mastera€?s thesis, University of Texas at Austin, Center for Transportation Research.>3. Morgan, Edward. 2010. a€?UT ASR DEF: Petrographic Analysis.a€? Unpublished report, Texas Department of Transportation, Austin, TX.>4. Bauer, Stacy, et al. 2006. Alkali-Silica Reaction and Delayed Ettringite Formation in Concrete: A Litera - ture Review. CTR technical report 0-4085-1. Austin, TX: University of Texas at Austin, Center for Transportation Research. href="http://www.utexas.edu/research/ctr/pdf_reports/0_4085_1.pdf" title="http://www.utexas.edu/research/ctr/pdf_reports/0_4085_1.pdf" target="_blank">http://www.utexas.edu/research/ctr/pdf_reports/0_4085_1.pdf.>5. Deschenes, Dean J., Oguzhan Bayrak, and Kevin J. Folliard. 2009. ASR/DEF-Damaged Bent Caps: Shear Tests and Field Implications. Technical report 12- 8XXIA006. Austin, TX: University of Texas at Austin.href=" http://fsel.engr.utexas.edu/publications/docs/IAC-12-8XXIA006.pdf" title=" http://fsel.engr.utexas.edu/publications/docs/IAC-12-8XXIA006.pdf" target="_blank"> http://fsel.engr.utexas.edu/publications/docs/IAC-12-8XXIA006.pdf.