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Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Size Effect in Large Prestressed Concrete Deep Beams
Author(s): K. H. Tan, H. Y. Lu, and S. Teng
Publication: Structural Journal
Appears on pages(s): 937-946
Keywords: building codes; cracking (fracturing); deep beams; deflection; diagonal tension; prestressed concrete; shear strength.
Abstract:This paper presents an experimental investigation on the size effect in large prestressed-concrete deep beams. Twelve specimens with a total main-steel-and-strand ratio rc maintained close to 2.50% were tested to failure; two parameters were studied: viz. beam height h, ranging from 500 to 1750 mm, and shear-span-to-height ratio a/h, varying between 0.50 and 1.00. All of the beams had cylinder strengths of about 40 MPa; web reinforcement was omitted to study the effect of beam size on concrete shear strength. In comparison to reinforced-concrete deep beams, it is evident that prestressing improves the diagonal cracking and serviceability strengths and generally enhances ultimate shear capacity if bearing failure can be prevented. Test results reveal that the ultimate shear stress is size-dependent but the diagonal cracking stress is not. With increasing h, prestressed deep beams tend to be more brittle, even though the brittleness is somewhat offset by the location and degree of prestressing. The 12 test results are then compared with predictions based on the American ACI Code, the Canadian CSA Code, and the U.K. CIRIA. The CSA Code predictions provide uniform safety margin for large-and medium-sized beams, but conservatism in both the ACI and CIRIA predictions reduces with increasing h and a/h ratio. An explanation is also given for the uniform safety margin predicted by the CSA Code.
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