Experimental Study of the Axial Compression–Bending Interaction Behavior of Square Fiber–Reinforced Concrete Columns with GFRP Reinforcement

Glass fiber–reinforced polymer (GFRP)–RC columns can fail in a brittle manner under combined axial compression and bending moment. Discrete macrofiber addition can improve the pseudoductility of GFRP-RC elements by enhancing postpeak behavior. This study attempts to develop the axial compression (P)–bending moment (M) interaction diagram for GFRP-RC columns with discrete macrofibers. Two types of discrete fibers, namely synthetic and hybrid (synthetic and steel), with three different dosages, are considered to understand the effectiveness of fiber type and fiber dosages. Four combinations of axial load–bending moment cases are considered to develop the P-M interaction behavior of GFRP fiber–reinforced concrete (FRC) columns. The results revealed that hybrid fiber–reinforced columns showed higher capacity and increased deformation index than counterpart synthetic polyolefin FRC columns at the same dosages under all combinations of bending and axial compression loads. The contribution of GFRP rebars to the overall load resistance improved significantly due to fiber addition at all combinations of axial load and bending moment. Moreover, the deformability factor also increased in all scenarios when fibers were added. At higher dosages of fibers, the columns demonstrated enhanced strength and ductility, along with the increased strain of GFRP rebars at peak loads.