Strength of bearing area confined by fiber-reinforced concrete

The research project described in this paper examined the influence of steel fiber-reinforced concrete (SFRC) on the strength of confined bearing areas. Twenty-four 12 x 24 in. (300 x 610 mm) cylindrical specimens were loaded to failure through 6 and 3 in. (150 and 75 mm) diameter bearing plates. Experimental variables included transverse reinforcement ratios ranging between 0.0 and 0.8%, and steel fiber dosages between 0.0 and 1.5% by volume. Specimens were uniaxially loaded to failure while displacement and load data were collected. Increases in bearing strength between 12 and 38% were obtained for specimens with 1% fibers when compared to similar specimens not containing fibers. Upon conclusion of this study, the authors observed that bearing areas surrounded by concrete containing steel fibers were able to attain a higher resistance to bearing loads than specimens without fibers. As a result, bearing areas confined by SFRC, and by steel fibers in combination with stirrups, may potentially be relied on to resist larger compressive loads than areas not reinforced with steel fibers. The findings of this study support an increase of the ACI 318-11 (Section 10.14) bearing strength limitation for areas surrounded by SFRC.