Impact resistance of reinforced ultra-high-performance concrete beams with different steel fibers

Ten large reinforced ultra-high-performance concrete (UHPC) beams were fabricated and tested under drop-weight impacts. The test parameters included the potential energy, fiber volume content, and steel fiber type and length. The important parameters obtained from an experimental program were summarized to provide a fundamental data set belonging to a research area that is limited within the literature. The test results showed that the addition of 2% (by volume) steel fibers was effective in decreasing the maximum and residual deflections by impact, improving residual capacities after impact damage, redistributing the tensile stress associated with microcracking, and preventing local failure at the contact surface. The use of long smooth steel fibers also resulted in the improvement of both the impact and residual capacities-that is, a decrease in the maximum and residual deflections by impact and an increase in the residual moment capacity and deflection capacity at the ultimate state. In contrast, the fiber content and type had negligible influences on the ratios of the moment capacities under impact and quasi-static loadings. Finally, a step-by-step procedure to assess the residual capacities after impact damage was proposed based on the quasi-static flexural response and the maximum deflection by impact.