Shear Design Performance of Beams Reinforced with Steel Fibers and Stirrups

Many researchers have established the effectiveness of steel fibers in shear strength enhancement in RC beams. Use of steel fibers as shear reinforcements can be attractive in load bearing structures where beams span over window and door openings as well as in thin concrete section where conventional reinforcements can not be used. Moreover, in reinforced concrete frames, relief of stirrups in congested areas, crack control and ductility improvement can also be achieved with use of steel fibers. The fact that steel fiber reinforced concrete (SFRC) is a ready to use material implies that fabrication of stirrups and manual labor required for fixing is reduced or avoided. These merits result in robust and faster structure construction in which cost savings can be made leading to adequate and affordable supply of shelter. However, practical application of SFRC in RC beam is hampered by lack of design guidelines. In this study, a simple shear design method for steel fiber RC beams is proposed and tested. Preliminary tests were undertaken on six small RC beams reinforced with stirrups and variable amount of steel fibers (0.5% to1.5% content) determined to match the number of stirrups. Further tests were conducted on larger designed stirrup and fiber RC beams. Empirical shear strength formulations found in the literature for SFRC were applied as a check on the proposed design formulation. Test results confirmed the effectiveness of the proposed method and it is shown that fibrous beams posses a better shear resistance mechanism than that of an equivalently stirrup reinforced beams.