Ship collisions, groundings and penetration of objects through the shell plating of the ship can lead to loss of ship buoyancy and possibility to progressive flooding inside the ship. The size and location of the opening therefore define the seriousness of the incident and form initial conditions for the prediction of the flooding process and this way define also the time to evacuation and extent of the final damage. Therefore, prediction of the opening size has fundamental importance in ship safety assessment. Finnish coast is shallow and this increases possibility for groundings. Frequent cross-traffic further increases the risk of grounding. Cold temperature and its effects to hull girder temperature gradient makes the problem challenging as the steel used in shell plating is known to have temperature dependent stress-strain relation and also the fracture point. This project focuses on Finite Element simulations based on shell elements and their validation with material and structural testing. The study shows that use of shell elements is feasible as it can result in accurate predictions in reasonable computing time. However, this requires that the failure strain is defined based on both stress and strain state and element size instead of the commonly used scaling based purely on tensile testing.