Abstract: To study the influence of sand-expandable polyethylene (EPE) composite cushion on the damage and failure of reinforced concrete (RC) sheds, numerical simulations were performed by the coupled method of smooth particle hydrodynamics (SPH) and finite element method (FEM). A refined finite element model of a prototype RC shed with cushion was established. The reliability of adopted material constitutive models and numerical algorithms was validated by reproducing existing impact tests. The dynamic response and damage degree of RC sheds with/without traditional sand cushion and composite cushion under rockfall impacts were compared. The effects of the thickness ratio of sand to EPE in composite cushion, EPЕ density, rockfall mass and impact velocity on the rockfall impact resistance of RC sheds were examined through simulation analyses of parameter influence. The numerical simulation results indicate that: The roof of the shed without cushion suffers shear failure under the rockfall impact, while the roof of the shed with sand or composite cushion sustains flexural failure; Compared to traditional sand cushion, composite cushion can reduce the peak rockfall impact force by 36%, the bending moment of slab roof by 12%, the shear force by 56%, the vertical displacement by 60%, and the damage area by 64%, as well as effectively transform the rockfall impact force from the shed roof to the shed substruction; The rockfall impact resistance of sheds with composite cushion first increases and then decreases with the increase of the thickness ratio of sand to EPE, while decreases with the increase of EPE density.