A COMPARATIVE STUDY OF THE BEHAVIOUR OF HYBRID FIBER-REINFORCED CONCRETE (HFRC) BEAMS SUBJECTED TO LOW-VELOCITY IMPACT LOADS UNDER VARIOUS BOUNDARY CONDITIONS

This study investigates the structural behaviour of Hybrid Fiber-Reinforced Concrete (HFRC) beams with the incorporation of steel and polypropylene fibers, considering various boundary conditions under low-velocity impact loading. Forty-eight beams, each measuring (150x200x1800) mm, were modeled and analyzed using ABAQUS software. Half of these beams were subjected to simply supported conditions, while the other half were under fixed support. Two types of fibers were employed, with aspect ratios of 60 for steel fibers and 231 for polypropylene fibers, while maintaining a constant fiber volume fraction of 1% of the specimen's total volume. The impact load was applied using a 100 kg hammer with a tip diameter of 16 mm, resulting in a hemispherical contact area of 201 mm², at four different velocities: 3.13 m/s, 4.42 m/s, 5.43 m/s, and 6.11 m/s. The findings indicate that the addition of hybrid fibers led to a reduction in beam deflection for both boundary conditions studied. When subjected to different impact velocities, the response of the beams followed a distinct pattern. In the case of fixed supported beams, the deflection initially exhibited a linear behaviour, followed by a sinusoidal waveform. Conversely, for simply supported beams, the deflection INITIALLY DISPLAYED A LINEAR RESPONSE BEFORE TRANSITIONING INTO THE PLASTIC DEFORMATION STAGE.