The paper presents a new concept for designing using sandwich plates made of steel skins with light-weight concrete core for deck-like structures and other types of marine and offshore structures where accidental impact resistance is one of the main design criteria. A series of experiments has been carried out to evaluate the performance of the proposed steel-concrete-steel (i.e. SCS) composite sandwich structures under projectile impact load. The SCS Sandwich structures comprising steel faceplates acting compositely using innovative J-J shear connector with a compact fibre reinforced concrete core can replace stiffened steel plate, precast and reinforced concrete in deck-like structures. Its stiffness and strength are tailored to meet particular dynamic requirements. Local plate buckling is precluded. The SCS with J-J shear connector is simpler, performs better and is cost competitive.