Abstract:
To study the bond performance between steel-polyvinyl alcohol hybrid fiber high-performance concrete (Steel-Polyvinyl alcohol Hybrid Fiber High Performance Concrete, S-PVA HFHPC) and deformed steel bars under repeated loading after high temperatures, the volume fractions of steel fiber and PVA fiber, as well as the mineral powder replacement rate, were selected as orthogonal factors. Twenty-five groups of specimens were designed and fabricated. After exposure to target temperatures of 200℃, 400℃, 600℃, and 800℃, central pull-out tests under repeated loading were conducted to investigate the bond failure modes, bond stress-slip curves, and variations in bond strength of S-PVA HFHPC with deformed steel bars under different parameters. The experimental study showed that: All specimens after high-temperature exposure exhibited pull-out failure of the steel bars; the bond stress-slip curves were overall symmetric about the origin, displaying an inverted “S” shape, with a “pinching” phenomenon appearing in the middle of the curve; the incorporation of S-PVA hybrid fibers had a positive hybrid effect on the bond strength between concrete and steel bars, with steel fibers showing a more significant increase in bond strength; the bond strength of all specimen groups decreased with increasing target temperature, with the most significant improvement occurring at 200℃, reaching a maximum increase of 56.11%; the incorporation of S-PVA hybrid fibers significantly enhanced hysteretic energy dissipation capability and effectively suppressed the degradation of bond stress and unloading stiffness during repeated loading, with the minimum reduction rates of unloading stiffness and hysteretic energy being 28.33% and 1.60%, respectively; considering the material strength reduction after high temperature and the fiber reinforcement effect, a calculation formula for the bond strength of S-PVA HFHPC with deformed steel bars under repeated loading after high temperatures was established, providing a reference for the design and application of reinforced structures using S-PVA HFHPC under coupled conditions of high temperature and repeated loading.