Abstract: This study investigates the dynamic response and damage mechanisms of reinforced concrete (RC) sheds with gravel cushions under rockfall impacts through numerical simulations using LS-DYNA, and proposes a performance-based design method for rockfall impact resistance. A refined finite element model of a prototype RC shed with a gravel cushion was established. By replicating existing impact tests on RC slabs and cushion layers, the reliability of the numerical simulation method was validated. Comparisons were numerically performed on the damage degree, on the rockfall impact force and, on the deformation and bendingresponses of the shed roof under different impact conditions (rockfall mass: 10-60 t, impact velocity: 10-50 m/s). The research results showed that: the damage to the shed was concentrated at the impact location on the roof, while the inner walls and columns remained largely undamaged. As the rockfall impact energy increased, the bending response of the roof intensified, leading to greater deformation and more severe damage, causing the failure mode to transition from bending failure to bending-shear failure. Based on the simulated results, the ratio of the roof’s bending response induced by rockfall impact to its bending resistance capacity was adopted as a damage evaluation factor for RC sheds with gravel cushions. Then, four damage levels, i.e., minor, moderate and severe damage as well as partial collapse were defined, and three performance objectives for rockfall impact resistance were developed. Finally, a performance-based design method for RC sheds with gravel cushions against rockfall impacts was proposed and validated.