Experimental study on the plastic rotation capacity of reinforced high strength concrete beams

This paper describes an experimental study on the plastic rotation capacity of reinforced high strength concrete beams. Thirty-six beams with various compressive strengths of concrete, tensile reinforcement ratios, compressive reinforcement ratios, and patterns of loading (1 point loading and 2-point loading) were tested to evaluate the plastic rotation capacity, extreme fiber concrete compressive strain and equivalent plastic hinge length, etc. The same quantities were also obtained from numerical analysis and compared with experimental data. According to the results, the yield curvatures obtained from experiments turned out to be quite close to those obtained from theoretical approach. However, the experimental results for ultimate curvatures were significantly larger than those of theoretical prediction based on the assumption of ε_cu = 0.003. Based on these observations, a new formula for ultimate strain is proposed for high strength concrete beams. Also the test results for plastic rotation capacity were found to be closer to those obtained using moment-curvature relationship considering tension stiffening of concrete and shear effect than those obtained using equivalent plastic hinge length. This substantiates that for accurate evaluation of plastic rotation capacity the consideration of tension stiffening of concrete and shear effect is most important.