Development of the non linear model for RC beams

Abstract

The relationship between the moment and curvature of reinforced sections is a very important parameter for nonlinear analysis of RC framed structure. A clear view of the strength, stiffness, ductility, and energy dissipation capacity structure can be obtained from this relationship. The moment-curvature relationship would enable us to observe the strength reduction beyond the peak point and degradation of the flexural rigidity. The present study focuses on the momentcurvature (M-φ) relation of rectangular beam section. A user friendly software programme to generate moment-curvature relation of rectangular reinforced concrete beams developed using stress-strain curves of concrete and steel as per
IS 456:2000. A thorough study is done to see the how different parameters (such as0 grade of concrete and steel, effective cover, amount of tension steel reinforcement etc.) affect the moment-curvature relation. Also a study is done on the variation of neutral axis in an underreinforced
rectangular doubly reinforced section with varying strain in the extreme compression fiber of concrete.
It is found from the study that increasing tension steel reinforcement substantially increases the moment capacity of the section but reduces the ductility. Increase in the grade of concrete marginally increases moment capacity but substantially increases the ductility. Both moment
capacity and ductility of the beam decreases with the increase of effective cover. Fe 415 grade of steel makes the beam more ductile than that with Fe 500. It is observed that with the increase in the compressive strain in the extreme fiber the neutral axis depth initially increases followed by a steep decrease till the failure of the beam.