The behaviour of reinforced concrete deep beams is complex due to small shear span-to-depth ratios, which deviates its behaviour from the classical Bernoullis beam behaviour. Such behaviour is predominant in cases where members are supported over small spans carrying heavy concentrated or distributed loads. Such is the case in the structural members like pile cap, transfer girder, panel beam, strap beam in foundation, walls of rectangular water tank, shear wall etc. This paper reports on the influence of Poly propylene fibers combined with and without steel fibers on the stiffness, spall resistance and shear strength of RC deep beams. A total of 21 beams were tested to failure under two-point loading, which were compared with the ACI code provisions. The shear span-to-depth ratios adopted were 0.7 to 0.9 incorporating three steel fiber volume fractions of 0%, 1%, 1.25% along with two different fibers of Steel and Poly propylene with volume fractions of (1.0 + 0.0) %, and (1.0 + 1.0) %. The beams with shear span-to-depth ratios 0.7, 0.8 and 0.9 showed an increase of 21.9%, 23.43% and 23.9% in the ultimate load carrying capacity with combined steel and poly propylene fibers as replacement of web reinforcement with reference to that of the beam without web reinforcement. With the above combinations, the shear strength and stiffness of the beams have been found to be improved. When the horizontal shear reinforcement was increased, the shear strength was found to increase.
Ultimate strength analysis of RC deep beams using strut-and-tie models.
