Enhancing the Flexural Behavior of Over-Reinforced Concrete Beams

Abstract This study investigates the enhancement of ductility in over-reinforced concrete beams, which are distinguished by their friable breakdown, using various approaches applied in the compression zone. Brittleness increases in over-reinforced portions, leading to abrupt and unforeseen failures. Concrete design codes avoid usage of over-reinforced sections. However, excessive adding of reinforcement might reduce the depth of a beam. In the study, three methods were used. The initial strengthening technique consisted of concrete confinement achieved through the application of various transverse reinforcement systems, including helical stirrups, conventional stirrup ties, and steel wire mesh. To ensure proper fixation and alignment of these elements, two mild steel bars with a nominal diameter of 8 mm were incorporated at the top of the specimens to function as stirrup hangers and to contribute to enhancing the capacity of the compression zone. The improvement was placed in the compression zone under the applied load and extended to the surrounding area with a 300 mm length. The second strategy consists of using steel fiber-reinforced concrete within the compression zone. The final reinforcement configuration involved the placement of upper longitudinal steel bars with diameters of 12 mm and 16 mm, as well as Glass Fiber-Reinforced Polymer (GFRP) bars with a diameter of 12 mm, along the entire length of the specimens. The numerical simulation method was employed by ABAQUS software to conduct the investigation. FEM was validated by contrasting its results with the outcomes of experiments. The results conclude that the failure mode of the control beam changes from brittle to ductile failure for the three improvement methods, but the beams with steel fiber and helical stirrups are more valuable than the others. Subsequent numerical analyses explored various parameters to complete a parametric study on two groups (diameter and spacing of stirrup-ties in the compression zone). An increase in spacing exerts a detrimental influence on structural behavior, whereas an enlargement of stirrup-tie diameter yields a favorable effect.