High-strength self-consolidating concrete girders subjected to elevated compressive fiber stresses, part 2: Structural behavior

摘要

>The design of prestressed concrete members is restricted by the requirement that the extreme compressive fiber stress at midspan be less than 60% of the concrete compressive strength at release of prestressing. Thepurported purpose of this limit is to provide serviceability performance, but it places unnecessary limits on the capability of the materials. For this research program, six prestressed concrete girders were produced with high-strength, self-consolidating concrete and subjected to elevated compressive fiber stress levels ranging from 65% to 84% of initial concrete compressive strength at release of prestressing. Part 1 of this series analyzed time-dependent prestress losses and camber behavior and compared these values with the results from typical prediction methods. This second part examines the flexural and shear behavior of the same girders. The results of structural testing indicated little reduction in flexural capacity of girders subjected to elevated stress levels, but further testing in shear is needed to reduce the variability in the results. The results reported here suggest that an increase in the allowable compressive stress limit up to at least 70% of the initial concrete compressive strength at release of prestressing at any location is feasible.>References>1. Brewe, J., and J. J. Myers. 2010. target="_blank" title="High-Strength Self-Consolidating Concrete Girders Subjected to Elevated Compressive Fiber Stresses, Part 1: Prestress Loss and Camber Behavior." href="http://dx.doi.org/10.15554/pcij.09012010.59.77 ">High-Strength Self-Consolidating Concrete Girders Subjected to Elevated Compressive Fiber Stresses, Part 1: Prestress Loss and Camber Behavior. PCI Journal, V.  55, No. 4 (Fall): pp. 59-77. >2. Liniers, A. D. 1987. target="_blank" title="Microcracking of Concrete under Compression and Its Influence on Tensile Strength" href="http://dx.doi.org/10.1007/bf02472746 ">Microcracking of Concrete under Compression and Its Influence on Tensile Strength. Materials and Structures, V. 20, No. 116 (March): pp. 111-116. >3. Smadi, M. M., and F. O. Slate. 1989.target="_blank" title=" Microcracking of High and Normal Strength Concretes under Short- and Long-Term Loadings. " href="http://dx.doi.org/10.14359/2264 "> Microcracking of High and Normal Strength Concretes under Short- and Long-Term Loadings. ACI Materials Journal, V. 86, No. 2 (March-April): pp. 117-127. >4. Birrcher, D. B., R. G. Tuchscherer, D. Mraz, A. Castro, O. Bayrak, and M. E. Kreger. 2006. Effects of Increasing the Allowable Compressive Release Stress of Pretensioned Girders. In The PCI  National Bridge Conference: Proceedings, October 23-25, 2006, Grapevine, Texas. CD-ROM. >5. American Association of State Highway and Transportation Officials (AASHTO). 2007. AASHTO LRFD Bridge Design Specifications. 4th ed. Washington, DC: AASHTO. >6. ACI Committee 318. 2005. Building Code Requirements for Structural Concrete (ACI 318-05) and  Commentary (ACI 318R-05). Farmington Hills, MI: American Concrete Institute (ACI).>7. PCI Industry Handbook Committee. 2004. PCI Design Handbook: Precast and Prestressed Concrete. 6th ed.  Chicago, IL: PCI. >8. target="_blank" title="ASTM A416" href=" http://dx.doi.org/10.1520/a0416_a0416m-10 ">ASTM A416. Standard Specification for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete. West  Conshohocken, PA: ASTM International.>9. target="_blank" title="ASTM A615" href="http://dx.doi.org/10.1520/a0615_a0615m-09 ">ASTM A615. Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement. West Conshohocken, PA: ASTM International.>10. Collins, M. P., and D. Mitchell. 1991. Prestressed Concrete Structures.  Prentice-Hall Inc. >11. American Association of State Highway and Transportation Officials (AASHTO). AASHTO LRFD Bridge Design Specifications-2