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<p>This study investigates the shear behavior of high-strength concrete (HSC) beams with large circular web openings subjected to elevated temperatures. Internal (steel fibers at 0.5% and 1.0% by volume) and external (ferrocement jackets) retrofitting techniques were evaluated. Nine beams were experimentally tested, including solid control specimens, un-strengthened beams, and retrofitted beams. Exposure to 500&#xa0;°C resulted in a shear capacity reduction of up to 68% for beams with 150&#xa0;mm openings. After thermal exposure, steel fibers enhanced the residual shear strength by up to 16.4%, while ferrocement jackets achieved recovery levels of up to 14.5%. A parametric finite element study was conducted considering opening diameters ranging from 100 to 200&#xa0;mm and temperature levels between 400 and 600&#xa0;°C, demonstrating strong agreement with experimental results (average deviation ≤ 3%). The findings provide validated insights into the combined effects of geometric discontinuities and thermal degradation and support the development of effective retrofitting strategies for HSC beams under fire conditions.</p>

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Shear behavior of high-strength reinforced concrete beams with circular openings under fire exposure

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月22日

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  • Ahmed E. Sedawy,
  • Ashraf A. A. Beshr,
  • Islam Ali Mahmoud

摘要

This study investigates the shear behavior of high-strength concrete (HSC) beams with large circular web openings subjected to elevated temperatures. Internal (steel fibers at 0.5% and 1.0% by volume) and external (ferrocement jackets) retrofitting techniques were evaluated. Nine beams were experimentally tested, including solid control specimens, un-strengthened beams, and retrofitted beams. Exposure to 500 °C resulted in a shear capacity reduction of up to 68% for beams with 150 mm openings. After thermal exposure, steel fibers enhanced the residual shear strength by up to 16.4%, while ferrocement jackets achieved recovery levels of up to 14.5%. A parametric finite element study was conducted considering opening diameters ranging from 100 to 200 mm and temperature levels between 400 and 600 °C, demonstrating strong agreement with experimental results (average deviation ≤ 3%). The findings provide validated insights into the combined effects of geometric discontinuities and thermal degradation and support the development of effective retrofitting strategies for HSC beams under fire conditions.