High-velocity projectile impact resistance of reinforced concrete slabs with ultra-high performance concrete strengthening-A numerical study

This paper adopted numerical simulations to explore the high-velocity projectile impact (HVPI) performance of 180 mm thick reinforced concrete (RC) slabs with ultra-high performance concrete (UHPC) strengthening. Finite -element modelling of the RC slab and UHPC layer subjected to HVPI was firstly performed to verify the numerical model related to the local damage and projectile residual velocity. Then, the slab configuration parameters concerning the steel rebar layer number and grid size in the UHPC layer, the spacing between the RC slab and UHPC layer, and the layout positions of the UHPC layer were investigated to determine the optimal strength-ening strategy to resist projectile perforation. The numerical results demonstrated that snugly placing the UHPC layer without steel rebars upon the impact face of the RC slab was the most effective and efficient strengthening strategy. With the optimal slab configuration, the influences resulting from the unconfined compressive strength of UHPC, projectile mass and nose shape on the projectile perforation of UHPC strengthened RC slabs were explored. For each influencing factor, the relations between the projectile residual velocity and UHPC layer thickness were obtained at various projectile striking velocities. In the light of the simulated data, an empirical formula was established to estimate the ballistic limit of the 180 mm thick RC slab with UHPC strengthening..