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This thesis presents the outcome of an investigation into the experimental and theoretical flexural behavior and strength of doubly-reinforced concrete beams with and without hollow plastic spheres. Tests are conducted on two types of beams having simply supported end conditions. To obtain experimental results, a gradually increasing two-point loading is used up to collapse. The experimental load-deflection and load-strain curves are recorded. Theoretical analysis is based on developing non-linear moment-curvature relationships for cross sections with and without hollow spheres. These moment-curvature relationships are then coupled with three separate numerical methods namely, finite difference method, finite integral method and Newmark’s method to predict load-deflection relationships for both beams. These three approximate analysis methods gave practically the same results. In addition, a theoretical study is conducted to predict the load-deflection curves, and the cracking and collapse load indices of full-scale beams with and without hollow spheres. The predicted cracking and peak load values are in good agreement with those found in the laboratory experiments. The study shows that the use of hollow plastic spheres in reinforced concrete beams results in a substantial decrease in self-weight without compromising the ultimate strength. |
