Abstract
Reinforced concrete beams with discrete hooked-end steel fibers at 0.5% volume fraction are tested with a shear span to depth (a/d) ratio equal to 1.8. Digital image correlation (DIC) technique was used to obtain the full-filed displacements from the beam. The formation and propagation of a shear crack which directly influences the load response and the peak load in the load response of the beam is monitored using the displacement information available from DIC. There is a continuous increase in slip across the crack faces with increasing load, which produces an increase in the crack opening. The dilatant behavior indicated by the proportion of crack opening to slip displacement obtained from the control and the SFRC beams is identical. Failure in control beams is brittle and was produced by the opening of dominant shear crack within the shear span. At the peak load, the shear crack pattern in fiber reinforced concrete is identical to the crack pattern in the control beam. The fiber reinforced concrete beams exhibit post peak load carrying capacity with continued slip of the dominant shear crack. The crack bridging stress provided by the fibers results in a significant increase shear transfer across the crack which provides significant post-peak load carrying capacity with increasing slip of the shear crack.
Highlights
Often in shear critical members, the requirement of shear reinforcement leads to close spacing of stirrups
The load response of the steel fiber reinforced concrete (SFRC) beams is nominally similar to the load response obtained from the control specimens up to the peak load of the control beams
In the 0.5% SFRC beams, there is a small increase in the peak load when compared to the control beams
Summary
Often in shear critical members, the requirement of shear reinforcement leads to close spacing of stirrups. This problem is compounded while considering the ductile detailing requirements to meet the concerns of seismic design, which requires provision of extra stirrup. Methods of reducing steel congestion, which provide the required capacity and ductility have often involved the use of fiber reinforcement in concrete. Most of the data in the literature has been obtained for slender beams with shear span to depth (a/d) ratios greater than 2.5 in which beam action governs the failure. There is very limited data available from beams with low a/d ratio i.e short beams for which arch action governs the failure. For small a/d ratio, failure is shown to be produced by a shear crack within a small region [2, 3, 9], which allows for studying the behavior of the shear crack
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