Experimental and numerical behavior of hybrid-fiber-reinforced concrete compression members under concentric loading

The modern research is aimed to enhance the tensile properties of concrete so that its performance should be made better in various reinforced concrete structures. In the current study, twenty hybrid-fiber-reinforced concrete (HFRC) columns and one plain concrete column were cast to examine the effect of hybrid fibers on the axial capacity, load-deflection response and cracking patterns of columns under axial concentric loading. All specimens were square in cross section having a side length of 150 mm and a height of 1200 mm. Two different types of fibers were used; one is steel fibers (SF) and second is polypropylene fibers (PPF). Four different volumetric ratios of SF (0.7%, 0.8%, 0.9%, 1.0%) and five different ratios of PPF (0.1%, 0.3%, 0.5%, 0.7%, 0.9%) were used in the current study. The results indicate that the combination of 0.8% SF and 0.5% PPF performed well for load-carrying capacity and a combination of 0.9% SF and 0.3% PPF presented the best performance for the ductility of HFRC columns. Moreover, a constitutive finite element model (FEM) was proposed using concrete damaged plastic (CDP) model in ABAQUS for predicting the axial behavior and crack patterns of HFRC columns under concentric loading. A close agreement was observed between the experimental measurements and FE predictions. Finally, a detailed comparison of theoretical axial capacities of HFRC columns was performed using the predictions of various codes and proposed equations.