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

Abstract

This study investigates the effects of hooked-end fiber geometry and volume fraction on the flexural behavior of concrete pedestrian decks. To achieve this, three different fiber geometries, i.e., three-dimensional (3D), four-dimensional (4D), and five-dimensional (5D), and volume fractions of 0.37%, 0.6%, and 1.0% were considered. Test results indicate that a higher number of hook ends can more effectively enhance the flexural strength and flexural strength margin at all volume fractions than a lower number, so that the order of effectiveness of hooked-end fibers on the flexural strength parameters was as follows: 5D > 4D > 3D. To satisfy the ductility index of 0.39, the amounts of 3D, 4D, and 5D hooked steel fibers should be in the range of 0.98%‒1.10%. Moreover, at a fiber volume fraction of 1.0%, only multiple cracking behaviors were observed, and the numerical results indicated that the volume fraction should be equal to 1.0% to guarantee a deflection-hardening response of pedestrian decks, regardless of the hooked-end fiber geometry. Consequently, a 1.0% by volume of hooked-end steel fiber is recommended to replace the minimum longitudinal steel rebars and guarantee a ductile flexural behavior with multiple cracks for pedestrian decks made of high-strength concrete.

Model for estimating the flexural performance of concrete reinforced with hooked end steel fibers using three‐point bending tests

“…Values in parentheses within Table 3 (and in all tables in the paper) correspond to the coefficient of variation ( CV ). A data classification was defined in terms of the CV obtained from 3PBT performed in previous studies 6–8, 29–32 ; that is, a CV lower than 15% reflects slight variation, a CV ranging from 15% to 25% suggests intermediate variation, and CV greater than 25% reflects high variation. As shown in Table 3, air content increased with fiber dosage and number of hooked ends.…”

“…To calibrate the proposed model, a database with 236 results of 3PBT reported by Venkateshwaran et al, 6 Tiberti et al 29 and Galeote et al, 35 Soetens et al, 30 Montaignac et al, 38 Poh et al, 39 Barros et al, 40, 41 Pereira et al, 42 Barragan, 32 Bencardino, 31 Grimaldi et al, 43 Abdallah et al, 7 Lee et al 8 and Cuenca et al 12 was assembled. Corresponding values of compressive strength ( f c ), volumetric fraction ( V f ), aspect ratio ( l f /d f ), tensile strength ( f u ) and number of hooked ends of steel fibers ( N ) of each mixture evaluated are also included in Table 5.…”

“…For structural applications, steel is the most common material used for producing fibers due to the inherent high strength, ductility and durability of steel in concrete 1 . Previous studies 2–5 have reported the improved performance of concrete when hooked end fibers are used; it has been indicated that the performance of steel fiber reinforced concrete (SFRC) is enhanced as the number of hooked ends of the fibers increases 6–8 . In flexure‐controlled elements, the use of SFRC allows for a reduction of conventional reinforcement, and very importantly, of construction time and costs of transportation, bending and cutting activities, preparation and storage of steel deformed bars or welded wire meshes 3 .…”

Optimization of the Fine to Coarse Aggregate Ratio for the Workability and Mechanical Properties of High Strength Steel Fiber Reinforced Concretes

“…The volume fractions of steel fibers, cement, and water, as Hooked-ended steel fibers used in this investigation were as given in Figure 2, while their physico-mechanical properties are presented in Table 2. Hooked-ended steel fibers of 1% volume fraction were used, based on the recommendations of the available literature [18][19][20].…”

“…ACI 318 code [ 18 ] recommends incorporating 1% of volume fraction of hooked-end fibers to improve the ductile flexural behavior. The incorporation 0.98‒1.10% of hooked-end fibers was required to satisfy the minimum reinforcement ratio [ 19 ], and 1.0% volume fraction of fiber is required to achieve a multiple cracking behavior [ 20 ].…”