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چکیده
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This research investigates the post-heating performance of steel fiber reinforced self-compacting concrete (SFR-SCC) beams using experimental tests at both the material and elemental levels, as well as analytical methodologies. The study includes a series of forty-eight cylindrical specimens of SCC and SFR-SCC materials tested at elevated temperatures, with a peak temperature of 600°C, to document the degradation of mechanical properties such as compressive and tensile strength and Young’s modulus. Additionally, thirty-two identical beams (100×100×900 mm) were tested to evaluate their response under ambient and post-heating conditions. The flexural behavior of heat-damaged beams, both unstrengthened and strengthened using near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips, was carefully analyzed. Results indicate that incorporating steel fibers in SCC enhances tensile and bending behavior across varying temperatures, while slightly decreasing compressive strength and Young’s modulus. Strengthening heat-damaged SFR-SCC beams with one NSM-CFRP strip led to a significant improvement in flexural capacity, with an increase of up to 139 % compared to control specimens at ambient temperature. Furthermore, the addition of a second NSM-CFRP strip increased stiffness, toughness, and flexural strength by up to 213 %, though it shifted the failure mode from flexural to shear. Based on these results, a newly proposed analytical approach for estimating the ultimate load capacity of unstrengthened and strengthened SFR-SCC beams with NSM-CFRP strips at varying temperatures was developed and verified against the experimentally derived results.
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