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چکیده
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Using bar splices in reinforced concrete structures is inevitable due to transportation and construction limitations. On the other hand, executing lap splices in flexural members such as beams allows these members to potentially fail at the splice zone before reaching their ultimate flexural capacity. The failure of the beam at the splice location results from different factors, one of which is the exposure of concrete members to elevated temperatures. To address this, the flexural behavior of beams with lap-spliced bars after exposure to heat was examined, and the feasibility of improving their flexural performance by incorporating hybrid steelpolypropylene fibers was studied in the work. Here, 24 reinforced concrete beam specimens were constructed in 12 groups and exposed to the four-point bending test. Variables considered in the manufacturing and testing of these specimens included the splicing method (continuous reinforcement, simple lap splice, and hooked-end lap splice), concrete mix type (plain and fiber-reinforced), and exposure temperature (25 and 600 ◦C). Parameters under study included the load–deflection behavior, crack pattern, cracking load, ultimate load, failure mode, initial stiffness, effective stiffness, energy-absorption capacity, and ductility of the beams. The results indicated that exposing the spliced concrete beams to elevated temperatures changed the failure mode from flexural to splitting; however, adding hybrid fibers to the concrete mix improved the behavior of these members, with a more pronounced improvement in the specimens with the hooked-end splice. In addition, the simultaneous use of the hooked-end splice and hybrid fibers in the beams that had been exposed to heat prevented the splitting failure mode in these members. Furthermore, splicing the bar in the heated and unheated beam specimens lowered the energy-absorption capacity and ductility of the beams. The addition of fibers improved the energy absorption and ductility of the heated and unheated specimens, and the beams with the hooked-end splice showed a more significant improvement.
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