Indirect Ductility Evaluation of Hollow and Solid Concrete Beams Reinforced with GFRP Bars Under Repeated Loading

The use of Glass Fiber-Reinforced Polymer (GFRP) bars to reinforce concrete beams can provide high resistance to corrosion, high performance, high sustainability, and reasonable strength but with low ductility. This study focused on the structural behavior and indirect evaluation of the ductility index of hollow and solid beam specimens reinforced with GFRP bars, steel bars, or both (hybrid). Eight simply supported beam specimens with dimensions of 1200 mm (length), 150 mm (height), and 100 mm (width) were made using self-compacted concrete (SCC) and tested using two-point repeated loading. The tests results showed that the ultimate load capacity of the tested solid and hollow beams reinforced with GFRP bars were 78% and 67% higher than that of the corresponding solid and hollow beam specimens with steel-bar reinforcement. The measured energy absorption is “instantaneous” energy absorption because the residual stress disappears after the load is removed at the end of the test and any cracks will close due to the semi-linear response of the beam specimens reinforced with GFRP bars. Regarding the solid beam specimens, those containing GFRP bars showed an increase in energy absorption of 64–127% compared with the corresponding reference beams. The hollow beam specimens containing GFRP bars showed an increase in energy absorption of 21–68% compared with the corresponding reference beam containing three steel bars.