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Structural Engineering and Mechanics Volume 47, Number 2, July25 2013 , pages 185-207 DOI: https://doi.org/10.12989/sem.2013.47.2.185 |
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Improving design limits of strength and ductility of NSC beam by considering strain gradient effect |
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J.C.M. Ho and J. Peng
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| Abstract | ||
| In flexural strength design of normal-strength concrete (NSC) beams, it is commonly accepted that the distribution of concrete stress within the compression zone can be reasonably represented by an equivalent by a and B to stipulate the width and depth of the stress block. Currently in most of the reinforced concrete (RC) design codes, a and B are usually taken as 0.85 and 0.80 respectively for NSC. Nonetheless, in an experimental study conducted earlier by the authors on NSC columns, it was found that a increases significantly with strain gradient, which means that larger concrete stress can be developed in flexure. Consequently, less tension steel will be required for a given design flexural strength, which improves the ductility performance. In this study, the authors\' previously proposed strain-gradient-dependent concrete stress block will be adopted to produce a series of design charts showing the maximum design limits of flexural strength and ductility of singly-and boubly- NSC beams. Through the design charts, it can be verified that the consideration of strain gradient effect can improve significantly the flexural strength and ductility design limits of NSC beams. | ||
| Key Words | ||
| beams; concrete stress block; design; ductility; normal-strength concrete; strain gradient; strength | ||
| Address | ||
| J.C.M. Ho : School of Civil Engineering, The University of Queensland, QLD 4072, Australia J. Peng : Department of Civil Engineering, The University of Hong Kong, Hong Kong | ||