Concurrent flexural strength and ductility design of normal- and high-strength concrete beams

The post-peak flexural behaviour of reinforced normal- and high-strength concrete beams has been investigated using complete moment-curvature analysis taking into account the effect of strain reversal in the tension steel. The results reveal that the major factors influencing the flexural ductility of reinforced concrete beams are the concrete grade, compression and tension steels ratios, and compression and tension steels yield strengths. Generally, flexural ductility increases with increase of compression steel and its yield strength, but decreases with increase of tension steel and its yield strength. However, the effect of concrete grade on flexural ductility is more complicated. To quantify how these parameters affect the flexural ductility, the authors have proposed a parameter A as a measure of the degree of a beam section being under-or over-reinforced. Based on A, an equation for direct evaluation of flexural ductility is established. Furthermore, the authors have studied the interrelation between the flexural strength and ductility that could be concurrently achieved and presented the interrelation in the form of charts for design applications.