Evaluation of Moment Curvature Relationship of Reinforced Concrete Beam

Abstract

In accordance with the development of industrial society and the expansion of the magnitude of economies, structures have become larger and more complex. The safety and serviceability assessment of those complex structures necessitate the development of accurate and reliable methods and models for their analysis. As Reinforced concrete (RC) structures which are brittle compared to steel structures, it is very important to describe the behaviour of the RC structures under over-load conditions and estimate their ultimate strength accurately.

Increase grade of concrete offers many advantages in terms of performance, and also costs but its brittle behaviour is a major drawback in case of seismic application. Increase grade of concrete results in reducing ductility of member.

In this research analytical as well as experimental study is carried out to study effect of different grade of concrete such as M30, M40 and M50 on moment Curvature relationship of reinforced concrete beam section. A well-established model of Stress-Strain for concrete and steel material are used. Models showing relationship of Stress-Strain for both confined and unconfined concrete are studied. A MATLAB program is developed to derive Moment-Curvature relationship for RC beam elements.

An experimental study is carried out to evaluate moment Curvature relationship of singly under reinforced concrete beam section. Three sample specimens of dimension 120mm × 150mm × 1350mm are prepared and tested for each grade of concrete leading to total nine numbers of specimens. They are designed to tested under Two Point load flexural test.

It has been observed that with increase grade of concrete results in increasing moment resisting capacity of the section on the other side Curvature ductility reduces. It means for higher grade of concrete yield occurs later than lower grade concrete but ultimate rotation occurs earlier. Which lead to reduction in plastic hinge formation capacity of RC section. Apart this deflection of RC beam specimens can be compared with analytically by Macaulay's deflection method. Upto the yield load experimental results are nearer to analytical results due to constant flexure rigidity