Experimental study on torsional behavior of FRC and ECC beams reinforced with GFRP bars

The influence of fibers on the torsional behavior of GFRP reinforced concrete beams was studied. The polypropylene fiber (PP) was incorporated into concrete to improve the mechanical properties of the beams. A total of eight GFRP bars reinforced concrete beams with different fiber contents were tested under pure torsional loading. The test results indicated that the PP fibers could inhibit the crack propagations effectively, the spacing and width of the cracks were decreased. Under the allowable crack width of 0.7 mm, the torsional moment of the fiber reinforced concrete (FRC) beams and engineered cementitious composite (ECC) beams were 10% and 40% greater than ordinary concrete beams respectively. Besides, within the fiber contents of 1.5%, the utilization intensity of the stirrups were enhanced by the fibers, the more the fiber contents was, the greater the torsional strength and the toughness of the beams were improved. Finally, empirical formulas for both cracking and ultimate torsional moments of the beams were proposed, the predicted values had good agreements with the experimental results.