Influence of Fiber Content on Shear Capacity of Steel Fiber Reinforced Concrete Beams

Abstract

For shear-critical structural elements where the use of stirrups is not desirable, such as slabs or beams with reinforcement congestion, steel fibers can be used as shear reinforcement. The contribution of the steel fibers to the shear capacity lies in the action of the steel fibers bridging the shear crack, which increases the shear capacity and prevents a brittle failure mode. This study evaluates the effect of the amount of fibers in a concrete mix on the shear capacity of steel fiber reinforced concrete beams with mild steel tension reinforcement and without stirrups. For this purpose, twelve beams were tested. Five different fiber volume fractions were studied: 0.0%, 0.3%, 0.6%, 0.9%, and 1.2%. For each different steel fiber concrete mix, the concrete compressive strength was determined on cylinders and the tensile strength was determined in a flexural test on beam specimens. Additionally, the influence of fibers on the shear capacity is analyzed based on results reported in the literature, as well as based on the expressions derived for estimating the shear capacity of steel fiber reinforced concrete beams. The outcome of these experiments is that a fiber percentage of 1.2% or fiber factor of 0.96 can be used to replace minimum stirrups according to ACI 318-14 and a 0.6% fiber volume fraction or fiber factor of 0.48 to replace minimum stirrups according to Eurocode 2. A fiber percentage of 1.2% or fiber factor of 0.96 was observed to change the failure mode from shear failure to flexural failure. The results of this presented study support the inclusion of provisions for steel fiber reinforced concrete in building codes and provides recommendations for inclusion in ACI 318-14 and Eurocode 2, so that a wider adoption of steel fiber reinforced concrete can be achieved in the construction industry.

ANN-Based Shear Capacity of Steel Fiber-Reinforced Concrete Beams without Stirrups

“…The fiber factor F [125][126][127][128] takes into account the geometry of the fibers (length and diameter) [53,129], the amount of fibers (fiber volume fraction) [69,70,130], and the bond properties of the fibers, which depends on the fiber type [4,[131][132][133]. A challenge here was to ascribe bond properties to the less common fiber types that were encountered in the literature.…”

Enhancement of Concrete Properties using Steel Fibers - Review

“…The failure of the models used in the study [66] One of the studies that dealt with the type of failure and shear behavior of reinforced concrete beams was presented by researchers Torres and Eva [68] using (10) concrete beams without stirrups reinforcement and dimensions (100 * 120 * 970mm) steel fibers were used in proportions (0.0-0.3-0.6-0.9-1.2% ) with the specifications of length (60mm), diameter (0.75mm), tensile stress (1225MPa), and after examining the models, the researchers concluded that the percentage of steel fibers (1.2%) of the concrete volume can compensate for the use of the minimum shear reinforcing and the type of failure was for the beams For all ratios, shear failure, except for the beams that used (1.2%) steel fibers, the type of failure was Flexure Failure, and the following figure shows the models upon inspection…”

Effect of Fibers on Durability of Concrete: A Practical Review

“…Since FRC has high toughness and resistance to impact, its use may be beneficial in the precast industry due to reduced susceptibility to damage during transport and handling. Furthermore, the use of steel fibers has been shown to result in higher resistance to shear failure of reinforced concrete beams, thereby reducing the need for stirrups [ 20 , 21 , 22 ]. In compressed elements, conventional reinforcement (i.e., rebars) may be replaced by fiber reinforcement [ 23 ].…”