Role of Fibers in Controlling Failure Modes of High-Strength Concrete Beams

摘要

The paper investigates the shear strength and the failure modes of high strength concrete beams with and without steel fibers (f_c approx approx 110 MPa). Sixteen reinforced high strength concrete beams (3600x350x200 mm) were tested under different combinations of shear force and bending moment. The beams were singly reinforced and without shear (web) reinforcement. The test results indicated that the addition of steel fibers to high strength concrete increases the ultimate shear strength, improves the brittle characteristic and transforms the failure mode into a more ductile one. The average gain of the ultimate shear strength due to the addition of steel fibers varied from about 14percent to 141percent depending on the shear span to depth ratio and the longitudinal steel ratio. Four modes of failure of reinforced high strength concrete are clearly distinguished as; diagonal tension, shear compression, shear flexure, and flexural failure. In general, cracks in fiber reinforced concrete beams are closer, narrower, and more than those in beams without fibers. This reflects the effect of steel fibers in redistributing the streses beyond cracking.