Structural performance of nuclear containment structures and power plant facilities is of critical importance for public safety.The performance of concrete in a high-speed hard projectile impact is a complex problem due to a combination of multiple failure modes including brittle tensile fracture,crushing,and spalling.In this study,reinforced concrete (RC) and steel-concrete-steel sandwich (SCSS) panels are investigated under high-speed hard projectile impact.Two modeling techniques,smoothed particle hydrodynamics (SPH) and conventional finite element (FE) analysis with element erosion are used.Penetration depth and global deformation are compared between doubly RC and SCSS panels in order to identify the advantages of the presence of steel plates over the reinforcement layers.A parametric analysis of the front and rear plate thicknesses of the SCSS configuration showed that the SCSS panel with a thick front plate has the best performance in controlling the hard projectile.While a thick rear plate is effective in the case of a large and soft projectile as the plate reduces the rear deformation.The effects of the impact angle and impact velocity are also considered.It was observed that the impact angle for the flat nose missile is critical and the front steel plate is effective in minimizing penetration depth.