EFFECT OF MATERIAL PROPERTIES ON BEHAVIOR OF OVER-REINFORCED CONCRETE BEAMS

Reinforced concrete structures are made up of two materials with different characteristics, namely, concrete and steel. The typical stage in the load-deformation behavior of a reinforced concrete simply supported beam is highly nonlinear and the response can be roughly divided into three ranges of behavior: the uncracked elastic stage, the crack propagation stage and the plastic (yielding of steel or crushing of concrete) stage. The stressstrain relation of concrete is not only nonlinear, but is different in tension than in compression. A nonlinear numerical model has been developed considering material and geometric nonlinearities. Material nonlinearity is simulated by considering parabolic stressstrain relationship of concrete and bilinear relationship of reinforcing steel which can model both elastic-perfectly plastic and plastic strain hardening. The modified Newton-Raphson technique has been used for the solution of the nonlinear equations. The load-deformation behavior of the over-reinforced high strength concrete beams has been carried out with the model. From the analyses it is observed that for the high strength concrete the increase in steel content increases the strength and stiffness but decreases the ductility.