Analysis of Pull-Out Behaviour of Straight and Hooked End Steel Fibres

Abstract

The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study presents an empirical description of the axial force required to pull out a hooked end steel fibre from a cementitious matrix. It is based upon consistent experimental tests that show the force versus displacement plot is formed from a sequence of events in which partial and full debonding at the interface is followed by bending of the hook knee to raise the force to its maximum. A loss of peak force occurs with the reversed plasticity involved in a full straightening of the fibre that precedes the rapid sliding to its full removal under a falling force. The stages are assembled in the said order with a piecewise connection between linear segments and a curve of exponential decay. A power law can be introduced to describe the knee bending stage if preferred. The normalised co-ordinates were adopted for the simple mathematical discontinuous function of the full pull-out process. Normalising force and displacement for hooked fibre is based upon the maximum values found for straight fibre pull out. This would apply to an overall embedded length of unity and a unit peak force for a full debonding of straight fibre in similar materials. For hooked fibre the normalised co-ordinates given refer to the initiation and duration of each event to be tabulated at fractions of the embedded length with multiples of that force. Such predictions are seen to be in good agreement with average pull-out response curves.

Effects of the addition of short straight steel fibers on the strength and strains of high-strength concrete during compression

“…The adhesion of smooth, straight fibers to the matrix is due only to adhesion and friction, while fibers deformed in the process (e.g. hooked) are additionally conditioned by mechanical anchorage 36 . This observation provides a better understanding of the differences in the rate of descent of σ-ε curve parts in the results from our own research and those from the literature.…”

Flexural behavior and minimum reinforcement condition in hybrid‐reinforced concrete beams

“…On the other hand, a rigid-softening constitutive law has been used to describe the slippage of the short fibers. Following the suggestions reported in the literature on the basis of experimental pull-out tests, [47][48][49] different softening laws need to be considered in the case of straight steel fibers and hooked-end steel fibers. In the case of a straight fiber, the pull-out behavior is well described by a descending power law (Figure 4a; n = 0.5).…”

Flexural Behaviour of Two Ribbed SFRC Slab Reinforced with GFRP Bars

“…Therefore, steel fibres with a hooked end are utilised to resolve the issues. According to (Abdallah & Rees, 2019), the pullout value of physical testing for hooked-end steel fibres indicates that the fibres' maximum capacity is reached as they pull through. This indicates that at high deformations, the fibres reach their full capacity.…”