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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: Conservatism in Reinforced Concrete Frame Theory
Author(s): D.H. Clyde
Publication: Special Publication
Appears on pages(s): 383-403
Abstract:With discussion by M. Z. Cohn and D.H. Clyde. Existing design code requirements of English-speaking countries permit ultimate strength design. This method replaces the traditional stress analysis criteria of brittle behavior at stress level by brittle behavior at the level of moment capacity, possibly because limit design has been ruled out as unsuitable for rigorous design in reinforced concrete due to the limited ductility of concrete. Nevertheless, ultimate load methods have been proposed which allow limited redistribution by taking advantage of whatever ductility is available at moment level and checking against a deformation criterion. Design methods may be checked for conservatism by reference to the yield criterion (or interaction diagram for reinforced concrete cross sections) and to the theorems of limit design, particularly the lower bound theorem. This provides a necessary but not sufficient check on safety where there is a deformation criterion as well as a stress limit. It is shown that: 1. All methods which use an asymmetrical yield envelope and alternative loading systems can lead to unsafe designs; 2. the ultimate load method can lead to designs which satisfy the limit design uniqueness principle and, hence, violate certain assumptions of the method; and 3. the optimum limit design method, in solutions published by the proposers, violate the lower bound theorem of limit design. The correction of the deficiencies is straightforward in terms of the principles used to examine them but further development of the theories is necessary.
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