Significance of the shape of the assumed concrete compression block on the analysis and design of reinforced concrete sections under pure flexural loading

Abstract

The inelastic stress-strain relationship of concrete under compressive loading is difficult to express in mathematical terms. In flexural analysis and design of reinforced concrete sections, a number of simplified shapes have been proposed to date for the concrete compression block. The parabolicrectangular as well as the rectangular stress blocks are among the most common ones. In this study, the effect of assuming a parabolic-rectangular or rectangular shape of the concrete compression block on the analysis and design of reinforced concrete beams has been investigated. Analytical expressions are derived for the steel reinforcement ratio, the concrete compressive force coefficient and the design bending moment coefficient and the corresponding graphs are plotted in parallel. It is also shown with the aid of examples that the selected shape of the concrete compression block has little influence on the analysis and design of reinforced concrete rectangular sections.

Key words: Simplified stress block, Stress-strain, Parabolic-Rectangular, Flexure in RC sections