Abstract
This study examined the influences of fiber geometry, inclination angle, and loading rate on the pullout behavior of multiple steel fibers in ultra-high-performance concrete (UHPC). For this, two different steel fiber types, i.e., straight (S-) and hooked (H-), four different inclination angles (0°–60°), and four different loading rates (0.018 mm/s to 1200 mm/s) were considered. Test results indicated that the pullout performance of S-fibers in UHPC was improved by increasing the loading rate. The highest maximum pullout load of the S-fiber was obtained at the inclination angle of 30° or 45°. The maximum pullout loads of H-fibers also increased with increases in the loading rate, while their slip capacities rather decreased. No specific inclination angle was identified in the case of H-fibers that caused the highest maximum pullout load. The H-fibers yielded higher average bond strengths than S-fibers, but similar or even smaller pullout energies under the impact loads. The aligned S-fiber in UHPC was most sensitive to the loading rate compared to the inclined S-fiber and aligned H-fiber. The rate sensitivity became moderate with the fiber inclination angle. Consequently, the aligned S-fiber was recommended to achieve the best energy absorption capacity and interfacial bond strength at various impact loads.
Highlights
For several decades, concrete has been one of the most important construction materials because of its high compressive strength, durability, and low price
The slip steel fibers in ultra-high-performance concrete (UHPC) was gradually increased at the initial stage, while a speedy of steel fibers in UHPC was gradually increased at the initial stage, while a increase of the slip was obtained after reaching the peak load
In order examine the implications of the number and spacing of fibers on the dynamic pullout behavior and rate sensitivity, the previous test results reported by Tai and El-Tawil [24] were compared because similar mix proportions and steel fiber types were applied
Summary
Concrete has been one of the most important construction materials because of its high compressive strength, durability, and low price. Have examined the effects of the sand ratio, silica fume, and glass powder on the pullout behavior of single aligned straight steel fiber in UHPC at different particle sizes and with and without nanosilica particles. They [14] reported some important findings that improved dispersion of fine particles based on enhanced particle packing and the use of nanosilica particles achieved a slip hardening response up to large slips, thereby causing very high-equivalent bond strengths beyond 20 MPa. Yoo et al [16]. Have recently studied the pullout behavior of singly aligned and inclined twisted, hooked, and straight steel fibers in UHPC under quasi-static and impact loads. In order to rationally understand the pullout test results, failure modes, such as fiber pullout, rupture, and matrix spalling, were evaluated using image analyses, and the matrix spalling was quantitatively evaluated
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