Spacing and bundling effects on rate-dependent pullout behavior of various steel fibers embedded in ultra-high-performance concrete

Abstract

This study examines the effects of fiber geometry, spacing, and loading rate on the pullout resistance of steel fibers in ultrahigh-performance concrete (UHPC). For this, three different types of steel fibers, four different fiber spacings, and three different loading rates ranging from 0.018 to 740 mm/s were considered. Test results indicated that the single straight fiber in UHPC was most rate sensitive for pullout resistance, followed by the single twisted and then hooked fibers. The bond strengths and pullout energy of specimens with multiple straight fibers were improved by increasing the loading rate but were not affected by fiber spacing. Closer fiber spacing had a detrimental effect on the dynamic pullout resistance of multiple hooked steel fibers in UHPC, while no enhancement of average bond strength of multiple twisted fibers was observed as fiber spacing and loading rate varied. The average bond strengths of single and bundled hooked and twisted steel fibers in UHPC were clearly improved by increasing the loading rate. Bundling of fibers enhanced the impact pullout resistance of all the steel fibers in UHPC. The highest dynamic increase factors for the bundled straight, hooked, and twisted fibers were approximately 3.78, 1.57, and 1.41, respectively, at the impact loads.

Simultaneous prediction the strain and energy absorption capacity of ultra-high performance fiber reinforced concretes by using multi-output regression model

“…Hence, the inclusion of fibers improves the tensile capacity since they can transfer part of the matrix's tensile strength over the fissures and, under the right circumstances, even larger stresses [43,44]. Numerous studies [45][46][47][48][49] have been carried out to improve the reinforcing effectiveness of various types of steel fibers i.e., straight, hooked, twisted, and half-hooked in UHPC. Thus, the researchers developed new types of steel fibers, such as novel curvilinear steel fiber [50], slip-hardening straight steel fiber [51] and optimum engineered steel fibers [52] as well as improved fiber surface using an ethylenediaminetetraacetic acid electrolyte solution, cold gas plasma, and nanosilica coating [53].…”

Estudio numérico probabilístico de la capacidad resistente de tubos de HRFA con distribución aleatoria de fibras

“…Varios autores (11)(12)(13)(14)(15)(16) han estudiado este tema previamente a nivel material, analizando las causas de los cambios en la orientación y distribución de las fibras así como también la influencia que estos cambios producen en varias propiedades del material. Sin embargo, hay poca información en la literatura actual acerca de como estos cambios pueden afectar la resistencia mecánica de tubos de hormigón.…”

On the Pull-out Behavior of Hooked-End Shape Memory Alloys Fibers Embedded in Ultra-High Performance Concrete

“…Abdallah and Rees [18] compared the pull-out behavior of different types of hook fibers from ordinary concrete. Kim and Yoo [19] examined the effects of fiber spacing, geometry, and loading rate on the pullout resistance of steel fibers in Ultra-High-Performance…”