Residual load-carrying performance of ECC-RC composite beam after drop hammer impact

Abstract

Four types of specimens with various thicknesses of ECC layer in the tensile side of RC beam are fabricated. The influence of ECC layer on the dynamic response and residual capacity of RC beams is investigated through drop hammer impact test and post-impact static loading test. The results reveal that increasing the thickness of the ECC layer in the tensile side leads to less major cracks and more tiny cracks on the beam side under impact, and the damage of concrete in the impact zone alleviates. The incorporation of the ECC layer plays an insignificant role in displacement restitution and residual load-carrying capacity. However, ECC-RC composite beams effectively mitigate displacement ductility degradation. Compared to RC beam, ECC-RC composite beams also exhibit superior energy dissipation capacity at the post-impact loading stage. The parametric analysis indicates that a thicker ECC layer in composite beams with a low tensile reinforcement ratio effectively reduces maximum impact displacement but has a negligible influence on residual load-carrying capacity. In contrast, increasing the ECC layer in beams with a high tensile reinforcement ratio offers a limited reduction in maximum impact displacement but its residual load-carrying capacity significantly improves after impact.