Anchorage mechanisms of novel geometrical hooked-end steel fibres

Abstract

This study is aimed at fully understanding the anchorage mechanisms of steel fibres with novel hook geometries, e.g. 4DH and 5DH fibres, which were subjected to pull-out loading. The fibres were also embedded in four different matrixes with a compressive strength ranging from 33 to 148 MPa. The results showed that the anchorage and pull out behaviour was not only dependent on the geometry of the hooked end of steel fibres, but also closely related to the characteristics of matrix. Both maximum pullout load and total pull-out work of 5DH fibre were considerably higher than those of 4DH and the controlled 3DH fibres for all matrixes. All fibres embedded in normal strength concrete and medium strength concrete matrixes were completely pulled out without the occurrence of full deformation and straightening of the hook, while the controlled 3DH and 4DH fibres ruptured at hook portion when embedded in ultra-high performance mortar matrix. To fully utilize the high mechanical anchorage, 5DH fibres should be used for reinforcing high or ultra-high performance matrixes in practice.

Effects of Hooked-End Steel Fiber Geometry and Volume Fraction on the Flexural Behavior of Concrete Pedestrian Decks

“…The typical picture of 3D, 4D, and 5D hooked fibers used in this study is shown in Figure 1. The 5D hooked-end steel fiber provided 11% and 73% higher maximum pullout load and 53% and 92% higher pullout energy than the 4D and 3D hooked-end steel fibers, respectively [10]. Such a superior bond performance is achieved because of the improved mechanical anchorage, owing to the increased number of hook ends.…”

“…Owing to a better mechanical anchorage effect of the highly deformed hooked-end fibers, the order of bond performance was reported as follows: 5D > 4D > 3D [10]. Abdallah and Fan [10] noted that the maximum pullout load and energy absorption capacity of 5D hooked-end steel fibers embedded in normal-strength concrete are obviously higher than those of 3D and 4D fibers, respectively. In addition, three different volume fractions, i.e., 0.37%, 0.60%, and 1.00%, of hooked-end steel fibers were adopted to produce deflection-softening and deflection-hardening SFRCs, based on three-point bending test results [19].…”

“…The length and diameter of all 3D, 4D, and 5D hooked-end steel fibers were 60 mm and 0.9 mm, respectively, resulting in an aspect ratio (l f /d f ) of approximately 65. Owing to a better mechanical anchorage effect of the highly deformed hooked-end fibers, the order of bond performance was reported as follows: 5D > 4D > 3D [10]. Abdallah and Fan [10] noted that the maximum pullout load and energy absorption capacity of 5D hooked-end steel fibers embedded in normal-strength concrete are obviously higher than those of 3D and 4D fibers, respectively.…”

“…In recent years, some researchers [10][11][12][13][14] developed a novel multiple hook-end steel fiber and verified its effectiveness based on pullout and tensile tests. Abdallah and Fan [10] reported that the maximum pullout load and energy of conventional hooked-end steel fibers with three-dimensional (3D) geometry are significantly improved by using four-dimensional (4D) and five-dimensional (5D) geometries. The typical picture of 3D, 4D, and 5D hooked fibers used in this study is shown in Figure 1.…”

Comparisons Between Pull-Out Behaviour of Various Hooked-End Fibres in Normal–High Strength Concretes

“…Of these, Dramix hooked end fibres of 4D (double bend) and 5D (triple bend) geometries were developed specifically to increase the crack-bridging ability of SFRC. The high mechanical anchorage effect of these fibres was demonstrated in a number of prior studies showing that their strong bonding to the matrix resulted in a high resistance to pull-out (Abdallah and Fan 2017). Fibre with more a complex pre-deformed geometry place a higher complexity on the analysis of its pull-out response (Abdallah et al 2017c, d).…”