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Journal of Engineering Research

Journal of Engineering Research

Abstract

This paper presents the results of an experimental study involving nine simply supported beams featuring lap-spliced bars within the constant moment zone. All beams shared identical reinforcement details, including three longitudinal reinforcement bars (12 mm diameter) and two top reinforcement bars (8 mm diameter) for shear stirrup hanging. The lap-spliced specimens were created with a splice length of thirty times the bar diameter (360 mm). The study focused on two key parameters: the fiber content of hooked-end steel fibers used in the concrete mix and the presence of stirrups in the lap-splice region. The hooked-end steel fiber used was with an aspect ratio of 50 (Lf = 50 mm and df = 1.0 mm) and was incorporated into the concrete mix at varying volumetric contents ranging from 0% to 2%. For specimens with stirrups, two approaches were examined: only three closed stirrups in the splice zone (spaced at 180 mm) or seven closed stirrups (spaced at 90 mm) in the splice region.

To assess the behavior and ductility of the beams, four-point loading tests were conducted, during these experiments, beam deflection, steel strains, crack propagation, and failure modes were observed and recorded, and then all these results were compared to those of conventional concrete specimens with and without lap splice. The results revealed that increasing the fiber content in the concrete mix led to higher yielding and ultimate loads in the beams, as well as increasing beam ductility. Notably, lap splice beams with a fiber content starting from 1.5% showed a comparable behavior to the reference RC beam without lap splice.

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