SHEAR STRENGTH AND DUCTILITY OF BEAMS REINFORCED WITH SYNTHETIC MACRO-FIBERS

The application for synthetic macro fibers has been extended beyond shrinkage and cracking control to include some structural applications such as composite metal deck and industrial floors. One issue that has remained a matter of concern for engineers and designers is the shear behavior of the concrete when macro synthetic fibers are incorporated in the concrete mix. This paper is part of a recent research project that showed macro synthetic fibers to significantly improve the shear strength and ductility of reinforced concrete beams. The paper presents results from testing of 14 large beams under center-point monotonic loading. The beams were tested with a shear span to depth ratio of 2.3 and 3.5. The beam cross-section was 390 × 230 mm. Macro synthetic fibers were added at three volume fractions of 0.5 %, 0.75 %, and 1.0 %, which is equivalent to 4.6, 6.9, and 9.2 kg/m 3 . The results showed that the addition of macro synthetic fibers significantly improved the shear strength and ductility of the RC beams and modified the cracking and failure behavior. The ultimate shear strength of slender and short beams was increased up to 30% compared to the control RC beams.