Ultimate Strength and Cracking Resistance of Lightly Reinforced Beams


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Title: Ultimate Strength and Cracking Resistance of Lightly Reinforced Beams

Author(s): S. D. Lash

Publication: Journal Proceedings

Volume: 49

Issue: 2

Appears on pages(s): 573-582

Keywords: no keywords

Date: 2/1/1953

The ultimate strength of beams reinforced with 1 percent or less of inter-mediate grade steel is somewhat greater than that indicated by either the plastic or conventional theories. This is because the theories neglect the effect of concrete in tension below the neutral axis. The excess is not great except for beams made with high strength concrete and small amounts of steel. Cracking resistance of lightly reinforced beams depends upon the strength of the concrete and the amount of reinforcement. The tensile modulus of rupture of the concrete is increased significantly by the presence of reinforcement. Deflection of a beam at yield of steel is independent of the amount of steel, provided the ratio of reinforcement is 0.7 percent or more. Below this limit the deflection diminishes and may be quite small.