Ductility of Reinforced Concrete Beams

Abstract

Concrete structures are designed by satisfying two criteria namely, safety and serviceability. Safety criterion checks whether the structure is safe in carrying the designed load or not. Serviceability criterion checks whether the developed deflections and crack widths are within the permissible limits or not. The evaluation of adequate margin of safety of concrete structures against failure can be assured by the accurate prediction of ultimate load and the complete Moment-curvature response. If the moment-curvature relationship is available, then the strength, stiffness and the ductility characteristics of the cross-section can be predicted. In this paper, an attempt has been made to study the variation of the strength, stiffness and the ductility of the singly reinforced concrete beams of M25 and M35 grades, using Moment-Curvature diagrams. Working Stress Method and Limit State Method are used for designing the reinforced concrete beams. Force equilibrium equations, Strain compatibility equations and Material models are used in developing the Moment-curvature diagrams. The Concrete strain and the percentage of tension steel are the input parameters. It is observed that for a given percentage of Tension Steel, the Moment and the Curvature are increasing with respect to the increase in the Concrete strain. But the decrease in Curvature value with the increase in percentage of Tension Steel reduced the energy absorption capacity (ductility).