The growth of the LNG shipping market in arctic seas, due to the discovery of new gas fields in Northern regions, is a main motivation for research in the area of ice loads for ship structures. The focus of the present work is on accidental loads due to collisions with icebergs. More precisely, the scenario investigated includes an impact between small size iceberg shapes (modeled as rigid bodies) and the side of a LNG ship (realized in two different scantling versions: DNV class notation ICE-1A and standard class). Numerical simulations of these collisions are carried out using the non linear finite element software ABAQUS. The paper discusses the approximations made in order to model the impact within the software ambient. The final output of the work is represented by graphs providing the damage levels in the structures (penetration of the colliding object) as a function of the mass and shape of the iceberg and of the ship speed.