Abstract If steel manufactures usually comply with the minimum code specifications, the nominal yield strength of rebar can however be significantly exceeded in many countries, depending on the steel manufacturing processes. Such an increase in yield strength can have negative effects on the flexural behavior of beams designed as tension controlled, and reduce their ductility, an essential property in seismic resisting structures. An experimental and analytical study of the flexural behavior of reinforced concrete (RC) beams was conducted through the investigation of the Moment-Curvature relationships and the ultimate steel strains. The main variable was the level of the actual steel yield stress as compared to the nominal value. It was found that unexpectedly high values of steel yield stress reduce the beam ductility and violate the tension-control condition which was enforced in the design stage. Appropriate design corrections are proposed to account for high yield stress values in order to achieve the desired ductility of beams while maintaining the moment capacities.

This paper presents analytical and experimental results on ductility of reinforced lightweight concrete beams and columns in the form of moment curvature relationships, and compares the response with that of normal reinforced concrete members. The experimental part is limited to flexural tests on beams made of lightweight concrete. The latter is obtained with natural lightweight aggregates. Concrete and steel stress-strain models in compression and tension are integrated analytically through the section in order to derive the resulting moment and axial force. Lightweight concrete beams and columns showed a more ductile behavior than normal concrete members and the analytical model reproduced the response with very good accuracy. The lightweight ductility was more pronounced in columns subjected to axial compression forces and bending.