Torsional Response of Fiber Reinforced Concrete Beam

Abstract

External loads on RC elements develops internal actions like, axial force, shear force, bending moment and torsional moment. RC elements in structure are subjected to significant amount of torsional loading in addition of bending and shear force. To improve torsional resistance of structural elements fibers can be used in concrete elements. In fiber reinforced concrete, fiber acts as secondary reinforcement in concrete. Many types of fibers are widely used in concrete, which enhance the properties of concrete in terms of abrasion resistance, impact resistance and flexural capacity of beam elements. The major objective of the present work is to study the effect of polypropylene fiber, glass fiber and carbon fiber with three different proportions in concrete beam elements on torsional resistance. An experimental investigation is conducted on fiber reinforced concrete beam subjected to torsion and also include the mechanical properties of fiber reinforced concrete. The study is aimed to recognize optimum dosage of fibers for effective behavior of concrete beam under torsional loading. Total 21 beam specimens with M30 grade of concrete is prepared having same dimensions of 150 mm × 150 mm cross-section and 700 mm in length. Out of 21 beam specimens, 3 beam specimens as control beam specimens and 2 beam specimens for each dosage of fibers. The beam specimens are to be tested under torsional loading using specially fabricated torsion loading frame to investigate ultimate torsion, torque v/s twist behavior and failure pattern to be observed. Comparison of torque v/s twist, ultimate torque for beam specimens with different dosage of fibers has been done. Mechanical properties of fiber reinforced concrete much affected by the dispersion of fibers in concrete mix which is depending upon the method of mixing. Compressive strength of FRC improves up to 14% to 46% with increase the dosage of fibers and split tensile strength of FRC improves up to 63% with respect to control concrete. Ultimate torque exceeds up to 58% for FRC beam specimen with respect to control concrete beam specimen. Ultimate torque for PP-FRC beam specimen is improved with increase fiber dosage in concrete mix, when for GF-FRC and CF-FRC beam specimen ultimate torque is more at 0.15\% dosage of fiber. There is brittle and sudden failure observed for all the beam specimens under torsional loading.