Experimental study on shear-span to effective-depth ratio of steel fiber reinforced concrete T-beams

In this study, twelve reinforced concrete (RC) T-beams were tested to failure under two-point flexural loading to investigate the influence of shear span-to-effective depth ( a/d ) ratio on their ultimate resistance and failure modes. All test specimens had exactly same cross-section and longitudinal steel ratio without any transverse stirrups along their lengths. The percentage of steel fibers used in the concrete mix ranged from 0 to 1.5 %, whereas the values of a/d ratio were varied as 1.6, 2.5 and 3.0 for each case. Steel fiber reinforced concrete (SFRC) specimens exhibited the higher ultimate resistance, displacement ductility and flexural toughness as compared to the RC beams without steel fibers for all values of a/d ratio. The diagonal-tension (shear) mode of failure is noticed in the RC specimen for the a/d ratio of 3.0, whereas the flexural mode of failure is noticed for the SFRC specimen with 1 % steel fibers for the a/d ratio of 1.6. The flexural strengths of SFRC specimens as noted in the experiments are compared with the theoretical values predicted using the ultimate design approach.