Effect of material properties on ductility of reinforced concrete beams

Abstract

Reinforced concrete (RC) is one of the most important building materials and is widely used in civil engineering structures. The constituents of reinforced concrete such as concrete and steel are very complex due to their different mechanical properties. The stress-strain behavior of concrete under short term compression loading is considered parabolic and that of the steel is elastic plastic. Concrete and reinforcing steel are represented by separate material models that are combined together to describe the behavior of the RC beam sections. The end displacements of the steel element are assumed to be compatible with the boundary displacements of the concrete element which implied perfect bond between them. This paper presents the effects of materials properties such as concrete compressive strength, yield strength of steel and reinforcement content on the curvature ductility of singly reinforced concrete beams as well as doubly reinforced concrete beams. From the analyses, it is observed that the ductility of a singly RC beam decreases as the tension steel content is increased, and the presence of compression steel increases the ductility significantly. For the same reinforcement content the increase in compressive strength of concrete increases curvature ductility of reinforced concrete section and for a doubly reinforced section rate of increase of curvature is more than that of a singly reinforced section. However, the moment ratio increases at a relatively slow rate than that of singly reinforced beams. On the other hand the ductility of RC beams decreases as the strength of reinforcement is increased.